SERVER-13641 Pull TransactionExperiment up to top level request processor

44 files changed, 420 insertions, 263 deletions

diff --git a/src/mongo/db/cloner.cpp b/src/mongo/db/cloner.cpp
index 37d28f334ad..96dfea73572 100644
--- a/src/mongo/db/cloner.cpp
+++ b/src/mongo/db/cloner.cpp
@@ -558,7 +558,7 @@ namespace mongo {
             return Status::OK();
         }
         CmdClone() : Command("clone") { }
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             string from = cmdObj.getStringField("clone");
             if ( from.empty() )
                 return false;
@@ -583,10 +583,9 @@ namespace mongo {
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context context( dbname );
-            DurTransaction txn;
 
             Cloner cloner;
-            bool rval = cloner.go(&txn, context, from, opts, &clonedColls, errmsg);
+            bool rval = cloner.go(txn, context, from, opts, &clonedColls, errmsg);
 
             BSONArrayBuilder barr;
             barr.append( clonedColls );
@@ -630,7 +629,7 @@ namespace mongo {
                  "is placed at the same db.collection (namespace) as the source.\n"
                  ;
         }
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             string fromhost = cmdObj.getStringField("from");
             if ( fromhost.empty() ) {
                 errmsg = "missing 'from' parameter";
@@ -666,8 +665,7 @@ namespace mongo {
 
             cloner.setConnection( myconn.release() );
 
-            DurTransaction txn;
-            return cloner.copyCollection(&txn, collection, query, errmsg, true, false, copyIndexes);
+            return cloner.copyCollection(txn, collection, query, errmsg, true, false, copyIndexes);
         }
     } cmdCloneCollection;
 
@@ -782,7 +780,7 @@ namespace mongo {
             help << "usage: {copydb: 1, fromhost: <connection string>, fromdb: <db>, todb: <db>"
                  << "[, slaveOk: <bool>, username: <username>, nonce: <nonce>, key: <key>]}";
         }
-        virtual bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             string fromhost = cmdObj.getStringField("fromhost");
             bool fromSelf = fromhost.empty();
             if ( fromSelf ) {
@@ -813,7 +811,6 @@ namespace mongo {
                                              static_cast<Lock::ScopedLock*>( new Lock::GlobalWrite() ) :
                                              static_cast<Lock::ScopedLock*>( new Lock::DBWrite( todb ) ) );
 
-            DurTransaction txn;
 
             Cloner cloner;
             string username = cmdObj.getStringField( "username" );
@@ -847,7 +844,7 @@ namespace mongo {
                 cloner.setConnection(conn);
             }
             Client::Context ctx(todb);
-            return cloner.go(&txn, ctx, fromhost, cloneOptions, NULL, errmsg );
+            return cloner.go(txn, ctx, fromhost, cloneOptions, NULL, errmsg );
         }
     } cmdCopyDB;
 
diff --git a/src/mongo/db/commands.cpp b/src/mongo/db/commands.cpp
index 045e475568f..27aba2bf5ae 100644
--- a/src/mongo/db/commands.cpp
+++ b/src/mongo/db/commands.cpp
@@ -90,6 +90,15 @@ namespace mongo {
         return ResourcePattern::forExactNamespace(NamespaceString(ns));
     }
 
+    bool Command::newRun(TransactionExperiment* txn,
+                      const string& db,
+                      BSONObj& cmdObj,
+                      int options,
+                      string& errmsg,
+                      BSONObjBuilder& result,
+                      bool fromRepl) {
+        return run(db, cmdObj, options, errmsg, result, fromRepl);
+    }
 
     void Command::htmlHelp(stringstream& ss) const {
         string helpStr;
diff --git a/src/mongo/db/commands.h b/src/mongo/db/commands.h
index a679dc3e5ff..36fc09d3bd1 100644
--- a/src/mongo/db/commands.h
+++ b/src/mongo/db/commands.h
@@ -33,6 +33,7 @@ namespace mongo {
     class Client;
     class Database;
     class Timer;
+    class TransactionExperiment;
 
 namespace mutablebson {
     class Document;
@@ -70,8 +71,16 @@ namespace mutablebson {
                       normally do not want to log the command to the local oplog.
 
            return value is true if succeeded.  if false, set errmsg text.
+
+           Default impl forwards to private run(). It will go away soon.
         */
-        virtual bool run(const string& db, BSONObj& cmdObj, int options, string& errmsg, BSONObjBuilder& result, bool fromRepl = false ) = 0;
+        virtual bool newRun(TransactionExperiment* txn,
+                         const string& db,
+                         BSONObj& cmdObj,
+                         int options,
+                         string& errmsg,
+                         BSONObjBuilder& result,
+                         bool fromRepl = false );
 
         /**
          * This designation for the command is only used by the 'help' call and has nothing to do 
@@ -192,7 +201,8 @@ namespace mutablebson {
                                          int queryOptions = 0);
         static Command * findCommand( const string& name );
         // For mongod and webserver.
-        static void execCommand(Command* c,
+        static void execCommand(TransactionExperiment* txn,
+                                Command* c,
                                 Client& client,
                                 int queryOptions,
                                 const char *ns,
@@ -200,7 +210,8 @@ namespace mutablebson {
                                 BSONObjBuilder& result,
                                 bool fromRepl );
         // For mongos
-        static void execCommandClientBasic(Command* c,
+        static void execCommandClientBasic(TransactionExperiment* txn,
+                                           Command* c,
                                            ClientBasic& client,
                                            int queryOptions,
                                            const char *ns,
@@ -223,6 +234,11 @@ namespace mutablebson {
         static int testCommandsEnabled;
 
     private:
+        // This method is deprecated. It should only be used by commands that don't transactions
+        virtual bool run(const string& db, BSONObj& cmdObj, int options, string& errmsg, BSONObjBuilder& result, bool fromRepl = false ) {
+            invariant(false);
+        }
+
         /**
          * Checks to see if the client is authorized to run the given command with the given
          * parameters on the given named database.
@@ -242,6 +258,12 @@ namespace mutablebson {
                                           bool fromRepl);
     };
 
-    bool _runCommands(const char *ns, BSONObj& jsobj, BufBuilder &b, BSONObjBuilder& anObjBuilder, bool fromRepl, int queryOptions);
+    bool _runCommands(TransactionExperiment* txn,
+                      const char* ns,
+                      BSONObj& jsobj,
+                      BufBuilder& b,
+                      BSONObjBuilder& anObjBuilder,
+                      bool fromRepl,
+                      int queryOptions);
 
 } // namespace mongo
diff --git a/src/mongo/db/commands/apply_ops.cpp b/src/mongo/db/commands/apply_ops.cpp
index a189af5db6f..b86d8716d08 100644
--- a/src/mongo/db/commands/apply_ops.cpp
+++ b/src/mongo/db/commands/apply_ops.cpp
@@ -59,7 +59,7 @@ namespace mongo {
             // applyOps can do pretty much anything, so require all privileges.
             RoleGraph::generateUniversalPrivileges(out);
         }
-        virtual bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
 
             if ( cmdObj.firstElement().type() != Array ) {
                 errmsg = "ops has to be an array";
@@ -84,7 +84,6 @@ namespace mongo {
             // SERVER-4328 todo : is global ok or does this take a long time? i believe multiple 
             // ns used so locking individually requires more analysis
             Lock::GlobalWrite globalWriteLock;
-            DurTransaction txn;
 
             // Preconditions check reads the database state, so needs to be done locked
             if ( cmdObj["preCondition"].type() == Array ) {
@@ -132,7 +131,7 @@ namespace mongo {
                 invariant(Lock::nested());
 
                 Client::Context ctx(ns);
-                bool failed = applyOperation_inlock(&txn, ctx.db(), temp, false, alwaysUpsert);
+                bool failed = applyOperation_inlock(txn, ctx.db(), temp, false, alwaysUpsert);
                 ab.append(!failed);
                 if ( failed )
                     errors++;
@@ -163,7 +162,7 @@ namespace mongo {
                     }
                 }
 
-                logOp(&txn, "c", tempNS.c_str(), cmdBuilder.done());
+                logOp(txn, "c", tempNS.c_str(), cmdBuilder.done());
             }
 
             return errors == 0;
diff --git a/src/mongo/db/commands/cleanup_orphaned_cmd.cpp b/src/mongo/db/commands/cleanup_orphaned_cmd.cpp
index 5a851307535..fcc81a00c59 100644
--- a/src/mongo/db/commands/cleanup_orphaned_cmd.cpp
+++ b/src/mongo/db/commands/cleanup_orphaned_cmd.cpp
@@ -61,7 +61,8 @@ namespace mongo {
      *
      * If the collection is not sharded, returns CleanupResult_Done.
      */
-    CleanupResult cleanupOrphanedData( const NamespaceString& ns,
+    CleanupResult cleanupOrphanedData( TransactionExperiment* txn,
+                                       const NamespaceString& ns,
                                        const BSONObj& startingFromKeyConst,
                                        bool secondaryThrottle,
                                        BSONObj* stoppedAtKey,
@@ -116,7 +117,8 @@ namespace mongo {
 
         // Metadata snapshot may be stale now, but deleter checks metadata again in write lock
         // before delete.
-        if ( !getDeleter()->deleteNow( ns.toString(),
+        if ( !getDeleter()->deleteNow( txn,
+                                       ns.toString(),
                                        orphanRange.minKey,
                                        orphanRange.maxKey,
                                        keyPattern,
@@ -177,7 +179,8 @@ namespace mongo {
         // Output
         static BSONField<BSONObj> stoppedAtKeyField;
 
-        bool run( string const &db,
+        bool newRun( TransactionExperiment* txn,
+                  string const &db,
                   BSONObj &cmdObj,
                   int,
                   string &errmsg,
@@ -231,7 +234,8 @@ namespace mongo {
             }
 
             BSONObj stoppedAtKey;
-            CleanupResult cleanupResult = cleanupOrphanedData( NamespaceString( ns ),
+            CleanupResult cleanupResult = cleanupOrphanedData( txn,
+                                                               NamespaceString( ns ),
                                                                startingFromKey,
                                                                secondaryThrottle,
                                                                &stoppedAtKey,
diff --git a/src/mongo/db/commands/collection_to_capped.cpp b/src/mongo/db/commands/collection_to_capped.cpp
index 0ed6f1bc15d..f1a375e6694 100644
--- a/src/mongo/db/commands/collection_to_capped.cpp
+++ b/src/mongo/db/commands/collection_to_capped.cpp
@@ -142,7 +142,7 @@ namespace mongo {
                                              NamespaceString(dbname, collection)),
                                      targetActions));
         }
-        bool run(const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
             string from = jsobj.getStringField( "cloneCollectionAsCapped" );
             string to = jsobj.getStringField( "toCollection" );
             double size = jsobj.getField( "size" ).number();
@@ -155,9 +155,8 @@ namespace mongo {
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(dbname);
-            DurTransaction txn;
 
-            Status status = cloneCollectionAsCapped( &txn, ctx.db(), from, to, size, temp, true );
+            Status status = cloneCollectionAsCapped( txn, ctx.db(), from, to, size, temp, true );
             return appendCommandStatus( result, status );
         }
     } cmdCloneCollectionAsCapped;
@@ -197,12 +196,11 @@ namespace mongo {
             return std::vector<BSONObj>();
         }
 
-        bool run(const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
             // calls renamecollection which does a global lock, so we must too:
             //
             Lock::GlobalWrite globalWriteLock;
             Client::Context ctx(dbname);
-            DurTransaction txn;
 
             Database* db = ctx.db();
 
@@ -222,28 +220,28 @@ namespace mongo {
             string longTmpName = str::stream() << dbname << "." << shortTmpName;
 
             if ( db->getCollection( longTmpName ) ) {
-                Status status = db->dropCollection( &txn, longTmpName );
+                Status status = db->dropCollection( txn, longTmpName );
                 if ( !status.isOK() )
                     return appendCommandStatus( result, status );
             }
 
-            Status status = cloneCollectionAsCapped( &txn, db, shortSource, shortTmpName, size, true, false );
+            Status status = cloneCollectionAsCapped( txn, db, shortSource, shortTmpName, size, true, false );
 
             if ( !status.isOK() )
                 return appendCommandStatus( result, status );
 
             verify( db->getCollection( longTmpName ) );
 
-            status = db->dropCollection( &txn, longSource );
+            status = db->dropCollection( txn, longSource );
             if ( !status.isOK() )
                 return appendCommandStatus( result, status );
 
-            status = db->renameCollection( &txn, longTmpName, longSource, false );
+            status = db->renameCollection( txn, longTmpName, longSource, false );
             if ( !status.isOK() )
                 return appendCommandStatus( result, status );
 
             if (!fromRepl)
-                logOp(&txn, "c",(dbname + ".$cmd").c_str(), jsobj);
+                logOp(txn, "c",(dbname + ".$cmd").c_str(), jsobj);
             return true;
         }
     } cmdConvertToCapped;
diff --git a/src/mongo/db/commands/compact.cpp b/src/mongo/db/commands/compact.cpp
index 97508e62b5f..a469347d677 100644
--- a/src/mongo/db/commands/compact.cpp
+++ b/src/mongo/db/commands/compact.cpp
@@ -83,7 +83,7 @@ namespace mongo {
             return IndexBuilder::killMatchingIndexBuilds(db->getCollection(ns), criteria);
         }
 
-        virtual bool run(const string& db, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& db, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             string coll = cmdObj.firstElement().valuestr();
             if( coll.empty() || db.empty() ) {
                 errmsg = "no collection name specified";
@@ -145,7 +145,6 @@ namespace mongo {
             Lock::DBWrite lk(ns.ns());
             BackgroundOperation::assertNoBgOpInProgForNs(ns.ns());
             Client::Context ctx(ns);
-            DurTransaction txn;
 
             Collection* collection = ctx.db()->getCollection(ns.ns());
             if( ! collection ) {
@@ -162,7 +161,7 @@ namespace mongo {
 
             std::vector<BSONObj> indexesInProg = stopIndexBuilds(ctx.db(), cmdObj);
 
-            StatusWith<CompactStats> status = collection->compact( &txn, &compactOptions );
+            StatusWith<CompactStats> status = collection->compact( txn, &compactOptions );
             if ( !status.isOK() )
                 return appendCommandStatus( result, status.getStatus() );
 
diff --git a/src/mongo/db/commands/create_indexes.cpp b/src/mongo/db/commands/create_indexes.cpp
index ddc9fa9b535..06b0b6e20b7 100644
--- a/src/mongo/db/commands/create_indexes.cpp
+++ b/src/mongo/db/commands/create_indexes.cpp
@@ -70,7 +70,7 @@ namespace mongo {
             return b.obj();
         }
 
-        virtual bool run( const string& dbname, BSONObj& cmdObj, int options,
+        virtual bool newRun(TransactionExperiment* txn,  const string& dbname, BSONObj& cmdObj, int options,
                           string& errmsg, BSONObjBuilder& result,
                           bool fromRepl = false ) {
 
@@ -167,13 +167,12 @@ namespace mongo {
             Client::WriteContext writeContext( ns.ns(),
                                                storageGlobalParams.dbpath,
                                                false /* doVersion */ );
-            DurTransaction txn;
             Database* db = writeContext.ctx().db();
 
-            Collection* collection = db->getCollection( &txn, ns.ns() );
+            Collection* collection = db->getCollection( txn, ns.ns() );
             result.appendBool( "createdCollectionAutomatically", collection == NULL );
             if ( !collection ) {
-                collection = db->createCollection( &txn, ns.ns() );
+                collection = db->createCollection( txn, ns.ns() );
                 invariant( collection );
             }
 
@@ -191,7 +190,7 @@ namespace mongo {
                     }
                 }
 
-                status = collection->getIndexCatalog()->createIndex(&txn, spec, true);
+                status = collection->getIndexCatalog()->createIndex(txn, spec, true);
                 if ( status.code() == ErrorCodes::IndexAlreadyExists ) {
                     if ( !result.hasField( "note" ) )
                         result.append( "note", "index already exists" );
@@ -205,7 +204,7 @@ namespace mongo {
 
                 if ( !fromRepl ) {
                     std::string systemIndexes = ns.getSystemIndexesCollection();
-                    logOp( &txn, "i", systemIndexes.c_str(), spec );
+                    logOp( txn, "i", systemIndexes.c_str(), spec );
                 }
             }
 
diff --git a/src/mongo/db/commands/drop_indexes.cpp b/src/mongo/db/commands/drop_indexes.cpp
index f7655fdbcb3..ea60d797f69 100644
--- a/src/mongo/db/commands/drop_indexes.cpp
+++ b/src/mongo/db/commands/drop_indexes.cpp
@@ -92,12 +92,11 @@ namespace mongo {
         }
 
         CmdDropIndexes() : Command("dropIndexes", false, "deleteIndexes") { }
-        bool run(const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& anObjBuilder, bool fromRepl) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& anObjBuilder, bool fromRepl) {
             Lock::DBWrite dbXLock(dbname);
-            DurTransaction txn;
-            bool ok = wrappedRun(&txn, dbname, jsobj, errmsg, anObjBuilder);
+            bool ok = wrappedRun(txn, dbname, jsobj, errmsg, anObjBuilder);
             if (ok && !fromRepl)
-                logOp(&txn, "c",(dbname + ".$cmd").c_str(), jsobj);
+                logOp(txn, "c",(dbname + ".$cmd").c_str(), jsobj);
             return ok;
         }
         bool wrappedRun(TransactionExperiment* txn,
@@ -213,7 +212,7 @@ namespace mongo {
             return IndexBuilder::killMatchingIndexBuilds(db->getCollection(ns), criteria);
         }
 
-        bool run(const string& dbname , BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool /*fromRepl*/) {
+        bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool /*fromRepl*/) {
             static DBDirectClient db;
 
             BSONElement e = jsobj.firstElement();
@@ -223,7 +222,6 @@ namespace mongo {
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(toDeleteNs);
-            DurTransaction txn;
 
             Collection* collection = ctx.db()->getCollection( toDeleteNs );
 
@@ -255,7 +253,7 @@ namespace mongo {
             }
             result.appendNumber( "nIndexesWas", collection->getIndexCatalog()->numIndexesTotal() );
 
-            Status s = collection->getIndexCatalog()->dropAllIndexes(&txn, true);
+            Status s = collection->getIndexCatalog()->dropAllIndexes(txn, true);
             if ( !s.isOK() ) {
                 errmsg = "dropIndexes failed";
                 return appendCommandStatus( result, s );
@@ -264,7 +262,7 @@ namespace mongo {
             for ( list<BSONObj>::iterator i=all.begin(); i!=all.end(); i++ ) {
                 BSONObj o = *i;
                 LOG(1) << "reIndex ns: " << toDeleteNs << " index: " << o << endl;
-                Status s = collection->getIndexCatalog()->createIndex(&txn, o, false);
+                Status s = collection->getIndexCatalog()->createIndex(txn, o, false);
                 if ( !s.isOK() )
                     return appendCommandStatus( result, s );
             }
diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index 34370d6907a..98aab888860 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -65,7 +65,7 @@ namespace mongo {
             find_and_modify::addPrivilegesRequiredForFindAndModify(this, dbname, cmdObj, out);
         }
         /* this will eventually replace run,  once sort is handled */
-        bool runNoDirectClient( const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
+        bool runNoDirectClient( TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
             verify( cmdObj["sort"].eoo() );
 
             const string ns = dbname + '.' + cmdObj.firstElement().valuestr();
@@ -96,7 +96,7 @@ namespace mongo {
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(ns);
             
-            return runNoDirectClient( ns , 
+            return runNoDirectClient( txn, ns , 
                                       query , fields , update , 
                                       upsert , returnNew , remove , 
                                       result , errmsg );
@@ -122,7 +122,8 @@ namespace mongo {
             result.append( "value" , p.transform( doc ) );
         }
 
-        static bool runNoDirectClient(const string& ns, 
+        static bool runNoDirectClient(TransactionExperiment* txn,
+                                      const string& ns, 
                                       const BSONObj& queryOriginal,
                                       const BSONObj& fields,
                                       const BSONObj& update,
@@ -134,8 +135,7 @@ namespace mongo {
 
             Lock::DBWrite lk( ns );
             Client::Context cx( ns );
-            DurTransaction txn;
-            Collection* collection = cx.db()->getCollection( &txn, ns );
+            Collection* collection = cx.db()->getCollection( txn, ns );
 
             const WhereCallbackReal whereCallback = WhereCallbackReal(StringData(ns));
 
@@ -222,7 +222,7 @@ namespace mongo {
             if ( remove ) {
                 _appendHelper(result, doc, found, fields, whereCallback);
                 if ( found ) {
-                    deleteObjects(&txn, cx.db(), ns, queryModified, true, true);
+                    deleteObjects(txn, cx.db(), ns, queryModified, true, true);
                     BSONObjBuilder le( result.subobjStart( "lastErrorObject" ) );
                     le.appendNumber( "n" , 1 );
                     le.done();
@@ -252,8 +252,7 @@ namespace mongo {
                     // the shard version below, but for now no
                     UpdateLifecycleImpl updateLifecycle(false, requestNs);
                     request.setLifecycle(&updateLifecycle);
-                    UpdateResult res = 
-                            mongo::update(&txn, cx.db(), request, &cc().curop()->debug());
+                    UpdateResult res = mongo::update(txn, cx.db(), request, &cc().curop()->debug());
                     if ( !collection ) {
                         // collection created by an upsert
                         collection = cx.db()->getCollection( ns );
@@ -298,11 +297,11 @@ namespace mongo {
             return true;
         }
         
-        virtual bool run(const string& dbname, BSONObj& cmdObj, int x, string& errmsg, BSONObjBuilder& result, bool y) {
-            static DBDirectClient db;
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int x, string& errmsg, BSONObjBuilder& result, bool y) {
+            DBDirectClient db(txn);
 
             if (cmdObj["sort"].eoo()) {
-                return runNoDirectClient(dbname, cmdObj, x, errmsg, result, y);
+                return runNoDirectClient(txn, dbname, cmdObj, x, errmsg, result, y);
             }
 
             const string ns = dbname + '.' + cmdObj.firstElement().valuestr();
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 7c39fee77e4..7a540a8a3ef 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -1208,7 +1208,7 @@ namespace mongo {
                 addPrivilegesRequiredForMapReduce(this, dbname, cmdObj, out);
             }
 
-            bool run(const string& dbname , BSONObj& cmd, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+            bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmd, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
                 Timer t;
                 Client& client = cc();
                 CurOp * op = client.curop();
@@ -1240,8 +1240,7 @@ namespace mongo {
 
                 BSONObjBuilder countsBuilder;
                 BSONObjBuilder timingBuilder;
-                DurTransaction txn;
-                State state( &txn, config );
+                State state( txn, config );
                 if ( ! state.sourceExists() ) {
                     errmsg = "ns doesn't exist";
                     return false;
@@ -1354,7 +1353,7 @@ namespace mongo {
 
                                 reduceTime += t.micros();
 
-                                txn.checkForInterrupt();
+                                txn->checkForInterrupt();
                             }
 
                             pm.hit();
@@ -1365,7 +1364,7 @@ namespace mongo {
                     }
                     pm.finished();
 
-                    txn.checkForInterrupt();
+                    txn->checkForInterrupt();
 
                     // update counters
                     countsBuilder.appendNumber("input", numInputs);
@@ -1447,7 +1446,7 @@ namespace mongo {
                 actions.addAction(ActionType::internal);
                 out->push_back(Privilege(ResourcePattern::forClusterResource(), actions));
             }
-            bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
+            bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
                 ShardedConnectionInfo::addHook();
                 // legacy name
                 string shardedOutputCollection = cmdObj["shardedOutputCollection"].valuestrsafe();
@@ -1464,8 +1463,7 @@ namespace mongo {
                 CurOp * op = client.curop();
 
                 Config config( dbname , cmdObj.firstElement().embeddedObjectUserCheck() );
-                DurTransaction txn;
-                State state(&txn, config);
+                State state(txn, config);
                 state.init();
 
                 // no need for incremental collection because records are already sorted
diff --git a/src/mongo/db/commands/rename_collection.cpp b/src/mongo/db/commands/rename_collection.cpp
index cd72f781707..07bf511141b 100644
--- a/src/mongo/db/commands/rename_collection.cpp
+++ b/src/mongo/db/commands/rename_collection.cpp
@@ -91,15 +91,14 @@ namespace mongo {
             IndexBuilder::restoreIndexes( indexesInProg );
         }
 
-        virtual bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             Lock::GlobalWrite globalWriteLock;
-            DurTransaction txn;
-            bool ok = wrappedRun(&txn, dbname, cmdObj, errmsg, result, fromRepl);
+            bool ok = wrappedRun(txn, dbname, cmdObj, errmsg, result, fromRepl);
             if (ok && !fromRepl)
-                logOp(&txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
+                logOp(txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
             return ok;
         }
-        virtual bool wrappedRun(DurTransaction* txn,
+        virtual bool wrappedRun(TransactionExperiment* txn,
                                 const string& dbname,
                                 BSONObj& cmdObj,
                                 string& errmsg,
diff --git a/src/mongo/db/commands/test_commands.cpp b/src/mongo/db/commands/test_commands.cpp
index 263b7af7f88..428298868b9 100644
--- a/src/mongo/db/commands/test_commands.cpp
+++ b/src/mongo/db/commands/test_commands.cpp
@@ -55,7 +55,7 @@ namespace mongo {
         virtual void help( stringstream &help ) const {
             help << "internal. for testing only.";
         }
-        virtual bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
             string coll = cmdObj[ "godinsert" ].valuestrsafe();
             log() << "test only command godinsert invoked coll:" << coll << endl;
             uassert( 13049, "godinsert must specify a collection", !coll.empty() );
@@ -64,17 +64,16 @@ namespace mongo {
 
             Lock::DBWrite lk(ns);
             Client::Context ctx( ns );
-            DurTransaction txn;
             Database* db = ctx.db();
             Collection* collection = db->getCollection( ns );
             if ( !collection ) {
-                collection = db->createCollection( &txn, ns );
+                collection = db->createCollection( txn, ns );
                 if ( !collection ) {
                     errmsg = "could not create collection";
                     return false;
                 }
             }
-            StatusWith<DiskLoc> res = collection->insertDocument( &txn, obj, false );
+            StatusWith<DiskLoc> res = collection->insertDocument( txn, obj, false );
             return appendCommandStatus( result, res.getStatus() );
         }
     };
@@ -134,7 +133,7 @@ namespace mongo {
         virtual void addRequiredPrivileges(const std::string& dbname,
                                            const BSONObj& cmdObj,
                                            std::vector<Privilege>* out) {}
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool) {
             string coll = cmdObj[ "captrunc" ].valuestrsafe();
             uassert( 13416, "captrunc must specify a collection", !coll.empty() );
             NamespaceString nss( dbname, coll );
@@ -142,7 +141,6 @@ namespace mongo {
             bool inc = cmdObj.getBoolField( "inc" ); // inclusive range?
 
             Client::WriteContext ctx( nss.ns() );
-            DurTransaction txn;
             Collection* collection = ctx.ctx().db()->getCollection( nss.ns() );
             massert( 13417, "captrunc collection not found or empty", collection);
 
@@ -155,7 +153,7 @@ namespace mongo {
                 Runner::RunnerState state = runner->getNext(NULL, &end);
                 massert( 13418, "captrunc invalid n", Runner::RUNNER_ADVANCED == state);
             }
-            collection->temp_cappedTruncateAfter( &txn, end, inc );
+            collection->temp_cappedTruncateAfter( txn, end, inc );
             return true;
         }
     };
@@ -182,27 +180,26 @@ namespace mongo {
             return IndexBuilder::killMatchingIndexBuilds(db->getCollection(ns), criteria);
         }
 
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             string coll = cmdObj[ "emptycapped" ].valuestrsafe();
             uassert( 13428, "emptycapped must specify a collection", !coll.empty() );
             NamespaceString nss( dbname, coll );
 
             Client::WriteContext ctx( nss.ns() );
-            DurTransaction txn;
             Database* db = ctx.ctx().db();
             Collection* collection = db->getCollection( nss.ns() );
             massert( 13429, "emptycapped no such collection", collection );
 
             std::vector<BSONObj> indexes = stopIndexBuilds(db, cmdObj);
 
-            Status status = collection->truncate(&txn);
+            Status status = collection->truncate(txn);
             if ( !status.isOK() )
                 return appendCommandStatus( result, status );
 
             IndexBuilder::restoreIndexes(indexes);
 
             if (!fromRepl)
-                logOp(&txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
+                logOp(txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
             return true;
         }
     };
diff --git a/src/mongo/db/commands/touch.cpp b/src/mongo/db/commands/touch.cpp
index 6427fba7b64..2011758f042 100644
--- a/src/mongo/db/commands/touch.cpp
+++ b/src/mongo/db/commands/touch.cpp
@@ -77,7 +77,8 @@ namespace mongo {
         }
         TouchCmd() : Command("touch") { }
 
-        virtual bool run(const string& dbname,
+        virtual bool newRun(TransactionExperiment* txn,
+                         const string& dbname,
                          BSONObj& cmdObj,
                          int,
                          string& errmsg,
@@ -104,7 +105,6 @@ namespace mongo {
             }
 
             Client::ReadContext context( nss.ns() );
-            DurTransaction txn;
 
             Database* db = context.ctx().db();
             Collection* collection = db->getCollection( nss.ns() );
@@ -114,7 +114,7 @@ namespace mongo {
             }
 
             return appendCommandStatus( result,
-                                        collection->touch( &txn,
+                                        collection->touch( txn,
                                                            touch_data, touch_indexes,
                                                            &result ) );
         }
diff --git a/src/mongo/db/commands/validate.cpp b/src/mongo/db/commands/validate.cpp
index d9d20610b45..3fba9dd4b00 100644
--- a/src/mongo/db/commands/validate.cpp
+++ b/src/mongo/db/commands/validate.cpp
@@ -59,7 +59,7 @@ namespace mongo {
         }
         //{ validate: "collectionnamewithoutthedbpart" [, scandata: <bool>] [, full: <bool> } */
 
-        bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+        bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
             string ns = dbname + "." + cmdObj.firstElement().valuestrsafe();
 
             NamespaceString ns_string(ns);
@@ -76,7 +76,6 @@ namespace mongo {
             }
 
             Client::ReadContext ctx(ns_string.ns());
-            DurTransaction txn;
 
             Database* db = ctx.ctx().db();
             if ( !db ) {
@@ -93,7 +92,7 @@ namespace mongo {
             result.append( "ns", ns );
 
             ValidateResults results;
-            Status status = collection->validate( &txn, full, scanData, &results, &result );
+            Status status = collection->validate( txn, full, scanData, &results, &result );
             if ( !status.isOK() )
                 return appendCommandStatus( result, status );
 
diff --git a/src/mongo/db/commands/write_commands/batch_executor.cpp b/src/mongo/db/commands/write_commands/batch_executor.cpp
index 160ed358bab..d7295a5458f 100644
--- a/src/mongo/db/commands/write_commands/batch_executor.cpp
+++ b/src/mongo/db/commands/write_commands/batch_executor.cpp
@@ -89,10 +89,12 @@ namespace mongo {
 
     using mongoutils::str::stream;
 
-    WriteBatchExecutor::WriteBatchExecutor( const BSONObj& wc,
+    WriteBatchExecutor::WriteBatchExecutor( TransactionExperiment* txn,
+                                            const BSONObj& wc,
                                             Client* client,
                                             OpCounters* opCounters,
                                             LastError* le ) :
+        _txn(txn),
         _defaultWriteConcern( wc ),
         _client( client ),
         _opCounters( opCounters ),
@@ -577,7 +579,10 @@ namespace mongo {
         }
     }
 
-    static void finishCurrentOp( Client* client, CurOp* currentOp, WriteErrorDetail* opError ) {
+    static void finishCurrentOp( TransactionExperiment* txn,
+                                 Client* client,
+                                 CurOp* currentOp,
+                                 WriteErrorDetail* opError ) {
 
         currentOp->done();
         int executionTime = currentOp->debug().executionTime = currentOp->totalTimeMillis();
@@ -600,8 +605,7 @@ namespace mongo {
         }
 
         if ( currentOp->shouldDBProfile( executionTime ) ) {
-            DurTransaction txn;
-            profile( &txn, *client, currentOp->getOp(), *currentOp );
+            profile( txn, *client, currentOp->getOp(), *currentOp );
         }
     }
 
@@ -614,18 +618,23 @@ namespace mongo {
     // - error
     //
 
-    static void singleInsert( const BSONObj& docToInsert,
+    static void singleInsert( TransactionExperiment* txn,
+                              const BSONObj& docToInsert,
                               Collection* collection,
                               WriteOpResult* result );
 
-    static void singleCreateIndex( const BSONObj& indexDesc,
+    static void singleCreateIndex( TransactionExperiment* txn,
+                                   const BSONObj& indexDesc,
                                    Collection* collection,
                                    WriteOpResult* result );
 
-    static void multiUpdate( const BatchItemRef& updateItem,
+    static void multiUpdate( TransactionExperiment* txn,
+                             const BatchItemRef& updateItem,
                              WriteOpResult* result );
 
-    static void multiRemove( const BatchItemRef& removeItem, WriteOpResult* result );
+    static void multiRemove( TransactionExperiment* txn,
+                             const BatchItemRef& removeItem,
+                             WriteOpResult* result );
 
     //
     // WRITE EXECUTION
@@ -644,7 +653,8 @@ namespace mongo {
         /**
          * Constructs a new instance, for performing inserts described in "aRequest".
          */
-        explicit ExecInsertsState(const BatchedCommandRequest* aRequest);
+        explicit ExecInsertsState(TransactionExperiment* txn,
+                                  const BatchedCommandRequest* aRequest);
 
         /**
          * Acquires the write lock and client context needed to perform the current write operation.
@@ -677,6 +687,8 @@ namespace mongo {
          */
         Collection* getCollection() { return _collection; }
 
+        TransactionExperiment* txn;
+
         // Request object describing the inserts.
         const BatchedCommandRequest* request;
 
@@ -796,7 +808,7 @@ namespace mongo {
         // particularly on operation interruption.  These kinds of errors necessarily prevent
         // further insertOne calls, and stop the batch.  As a result, the only expected source of
         // such exceptions are interruptions.
-        ExecInsertsState state(&request);
+        ExecInsertsState state(_txn, &request);
         normalizeInserts(request, &state.normalizedInserts);
 
         ElapsedTracker elapsedTracker(128, 10); // 128 hits or 10 ms, matching RunnerYieldPolicy's
@@ -832,7 +844,7 @@ namespace mongo {
         incOpStats( updateItem );
 
         WriteOpResult result;
-        multiUpdate( updateItem, &result );
+        multiUpdate( _txn, updateItem, &result );
 
         if ( !result.getStats().upsertedID.isEmpty() ) {
             *upsertedId = result.getStats().upsertedID;
@@ -840,7 +852,7 @@ namespace mongo {
 
         // END CURRENT OP
         incWriteStats( updateItem, result.getStats(), result.getError(), currentOp.get() );
-        finishCurrentOp( _client, currentOp.get(), result.getError() );
+        finishCurrentOp( _txn, _client, currentOp.get(), result.getError() );
 
         if ( result.getError() ) {
             result.getError()->setIndex( updateItem.getItemIndex() );
@@ -859,11 +871,11 @@ namespace mongo {
 
         WriteOpResult result;
 
-        multiRemove( removeItem, &result );
+        multiRemove( _txn, removeItem, &result );
 
         // END CURRENT OP
         incWriteStats( removeItem, result.getStats(), result.getError(), currentOp.get() );
-        finishCurrentOp( _client, currentOp.get(), result.getError() );
+        finishCurrentOp( _txn, _client, currentOp.get(), result.getError() );
 
         if ( result.getError() ) {
             result.getError()->setIndex( removeItem.getItemIndex() );
@@ -875,7 +887,9 @@ namespace mongo {
     // IN-DB-LOCK CORE OPERATIONS
     //
 
-    WriteBatchExecutor::ExecInsertsState::ExecInsertsState(const BatchedCommandRequest* aRequest) :
+    WriteBatchExecutor::ExecInsertsState::ExecInsertsState(TransactionExperiment* txn,
+                                                           const BatchedCommandRequest* aRequest) :
+        txn(txn),
         request(aRequest),
         currIndex(0),
         _collection(NULL) {
@@ -906,8 +920,7 @@ namespace mongo {
         _collection = database->getCollection(request->getTargetingNS());
         if (!_collection) {
             // Implicitly create if it doesn't exist
-            DurTransaction txn;
-            _collection = database->createCollection(&txn, request->getTargetingNS());
+            _collection = database->createCollection(txn, request->getTargetingNS());
             if (!_collection) {
                 result->setError(
                         toWriteError(Status(ErrorCodes::InternalError,
@@ -948,10 +961,10 @@ namespace mongo {
         try {
             if (state->lockAndCheck(result)) {
                 if (!state->request->isInsertIndexRequest()) {
-                    singleInsert(insertDoc, state->getCollection(), result);
+                    singleInsert(state->txn, insertDoc, state->getCollection(), result);
                 }
                 else {
-                    singleCreateIndex(insertDoc, state->getCollection(), result);
+                    singleCreateIndex(state->txn, insertDoc, state->getCollection(), result);
                 }
             }
         }
@@ -989,7 +1002,7 @@ namespace mongo {
                       result.getStats(),
                       result.getError(),
                       currentOp.get());
-        finishCurrentOp(_client, currentOp.get(), result.getError());
+        finishCurrentOp(_txn, _client, currentOp.get(), result.getError());
 
         if (result.getError()) {
             *error = result.releaseError();
@@ -1002,7 +1015,8 @@ namespace mongo {
      *
      * Might fault or error, otherwise populates the result.
      */
-    static void singleInsert( const BSONObj& docToInsert,
+    static void singleInsert( TransactionExperiment* txn,
+                              const BSONObj& docToInsert,
                               Collection* collection,
                               WriteOpResult* result ) {
 
@@ -1010,15 +1024,14 @@ namespace mongo {
 
         Lock::assertWriteLocked( insertNS );
 
-        DurTransaction txn;
-        StatusWith<DiskLoc> status = collection->insertDocument( &txn, docToInsert, true );
+        StatusWith<DiskLoc> status = collection->insertDocument( txn, docToInsert, true );
 
         if ( !status.isOK() ) {
             result->setError(toWriteError(status.getStatus()));
         }
         else {
-            logOp( &txn, "i", insertNS.c_str(), docToInsert );
-            txn.commitIfNeeded();
+            logOp( txn, "i", insertNS.c_str(), docToInsert );
+            txn->commitIfNeeded();
             result->getStats().n = 1;
         }
     }
@@ -1029,16 +1042,16 @@ namespace mongo {
      *
      * Might fault or error, otherwise populates the result.
      */
-    static void singleCreateIndex( const BSONObj& indexDesc,
+    static void singleCreateIndex( TransactionExperiment* txn,
+                                   const BSONObj& indexDesc,
                                    Collection* collection,
                                    WriteOpResult* result ) {
-        DurTransaction txn;
 
         const string indexNS = collection->ns().getSystemIndexesCollection();
 
         Lock::assertWriteLocked( indexNS );
 
-        Status status = collection->getIndexCatalog()->createIndex(&txn, indexDesc, true);
+        Status status = collection->getIndexCatalog()->createIndex(txn, indexDesc, true);
 
         if ( status.code() == ErrorCodes::IndexAlreadyExists ) {
             result->getStats().n = 0;
@@ -1047,12 +1060,13 @@ namespace mongo {
             result->setError(toWriteError(status));
         }
         else {
-            logOp( &txn, "i", indexNS.c_str(), indexDesc );
+            logOp( txn, "i", indexNS.c_str(), indexDesc );
             result->getStats().n = 1;
         }
     }
 
-    static void multiUpdate( const BatchItemRef& updateItem,
+    static void multiUpdate( TransactionExperiment* txn,
+                             const BatchItemRef& updateItem,
                              WriteOpResult* result ) {
 
         const NamespaceString nsString(updateItem.getRequest()->getNS());
@@ -1082,10 +1096,9 @@ namespace mongo {
         Client::Context ctx( nsString.ns(),
                              storageGlobalParams.dbpath,
                              false /* don't check version */ );
-        DurTransaction txn;
 
         try {
-            UpdateResult res = executor.execute(&txn, ctx.db());
+            UpdateResult res = executor.execute(txn, ctx.db());
 
             const long long numDocsModified = res.numDocsModified;
             const long long numMatched = res.numMatched;
@@ -1113,7 +1126,8 @@ namespace mongo {
      *
      * Might fault or error, otherwise populates the result.
      */
-    static void multiRemove( const BatchItemRef& removeItem,
+    static void multiRemove( TransactionExperiment* txn,
+                             const BatchItemRef& removeItem,
                              WriteOpResult* result ) {
 
         const NamespaceString nss( removeItem.getRequest()->getNS() );
@@ -1145,10 +1159,9 @@ namespace mongo {
         Client::Context writeContext( nss.ns(),
                                       storageGlobalParams.dbpath,
                                       false /* don't check version */);
-        DurTransaction txn;
 
         try {
-            result->getStats().n = executor.execute(&txn, writeContext.db());
+            result->getStats().n = executor.execute(txn, writeContext.db());
         }
         catch ( const DBException& ex ) {
             status = ex.toStatus();
diff --git a/src/mongo/db/commands/write_commands/batch_executor.h b/src/mongo/db/commands/write_commands/batch_executor.h
index c45443231ef..6406474e396 100644
--- a/src/mongo/db/commands/write_commands/batch_executor.h
+++ b/src/mongo/db/commands/write_commands/batch_executor.h
@@ -43,6 +43,7 @@ namespace mongo {
     class BSONObjBuilder;
     class CurOp;
     class OpCounters;
+    class TransactionExperiment;
     struct LastError;
 
     struct WriteOpStats;
@@ -58,7 +59,8 @@ namespace mongo {
         // State object used by private execInserts.  TODO: Do not expose this type.
         class ExecInsertsState;
 
-        WriteBatchExecutor( const BSONObj& defaultWriteConcern,
+        WriteBatchExecutor( TransactionExperiment* txn,
+                            const BSONObj& defaultWriteConcern,
                             Client* client,
                             OpCounters* opCounters,
                             LastError* le );
@@ -132,6 +134,8 @@ namespace mongo {
                             const WriteErrorDetail* error,
                             CurOp* currentOp );
 
+        TransactionExperiment* _txn;
+
         // Default write concern, if one isn't provide in the batches.
         const BSONObj _defaultWriteConcern;
 
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index f64c1fa7545..bcc297cf4b6 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -102,7 +102,8 @@ namespace mongo {
     // Write commands are counted towards their corresponding opcounters, not command opcounters.
     bool WriteCmd::shouldAffectCommandCounter() const { return false; }
 
-    bool WriteCmd::run(const string& dbName,
+    bool WriteCmd::newRun(TransactionExperiment* txn,
+                       const string& dbName,
                        BSONObj& cmdObj,
                        int options,
                        string& errMsg,
@@ -132,7 +133,8 @@ namespace mongo {
         // TODO: fix this for sane behavior where we query repl set object
         if ( getLastErrorDefault ) defaultWriteConcern = *getLastErrorDefault;
 
-        WriteBatchExecutor writeBatchExecutor(defaultWriteConcern,
+        WriteBatchExecutor writeBatchExecutor(txn,
+                                              defaultWriteConcern,
                                               &cc(),
                                               &globalOpCounters,
                                               lastError.get());
diff --git a/src/mongo/db/commands/write_commands/write_commands.h b/src/mongo/db/commands/write_commands/write_commands.h
index f8fccacc439..c94c505d5b5 100644
--- a/src/mongo/db/commands/write_commands/write_commands.h
+++ b/src/mongo/db/commands/write_commands/write_commands.h
@@ -72,7 +72,9 @@ namespace mongo {
         virtual bool shouldAffectCommandCounter() const;
 
         // Write command entry point.
-        virtual bool run(const string& dbname,
+        virtual bool newRun(
+                 TransactionExperiment* txn,
+                 const string& dbname,
                  BSONObj& cmdObj,
                  int options,
                  string& errmsg,
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index 2ee1b36f091..8914bb981d0 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -188,6 +188,7 @@ namespace mongo {
         }
 
         virtual void process( Message& m , AbstractMessagingPort* port , LastError * le) {
+            DurTransaction txn;
             while ( true ) {
                 if ( inShutdown() ) {
                     log() << "got request after shutdown()" << endl;
@@ -197,7 +198,7 @@ namespace mongo {
                 lastError.startRequest( m , le );
 
                 DbResponse dbresponse;
-                assembleResponse( m, dbresponse, port->remote() );
+                assembleResponse( &txn, m, dbresponse, port->remote() );
 
                 if ( dbresponse.response ) {
                     port->reply(m, *dbresponse.response, dbresponse.responseTo);
@@ -279,7 +280,9 @@ namespace mongo {
         logStartup();
         startReplication();
         if (serverGlobalParams.isHttpInterfaceEnabled)
-            boost::thread web( boost::bind(&webServerThread, new RestAdminAccess() /* takes ownership */));
+            boost::thread web( boost::bind(&webServerThread,
+                                           new RestAdminAccess(), // takes ownership
+                                           DurTransaction::factory) ); // XXX SERVER-13931
 
 #if(TESTEXHAUST)
         boost::thread thr(testExhaust);
@@ -289,8 +292,8 @@ namespace mongo {
 
 
     void doDBUpgrade( const string& dbName, DataFileHeader* h ) {
-        static DBDirectClient db;
         DurTransaction txn;
+        DBDirectClient db(&txn);
 
         if ( h->version == 4 && h->versionMinor == 4 ) {
             verify( PDFILE_VERSION == 4 );
diff --git a/src/mongo/db/dbcommands.cpp b/src/mongo/db/dbcommands.cpp
index 97ef4247644..16e59026bee 100644
--- a/src/mongo/db/dbcommands.cpp
+++ b/src/mongo/db/dbcommands.cpp
@@ -68,7 +68,6 @@
 #include "mongo/db/repl/is_master.h"
 #include "mongo/db/repl/oplog.h"
 #include "mongo/db/storage/extent_manager.h"
-#include "mongo/db/storage/mmap_v1/dur_transaction.h"
 #include "mongo/db/storage/mmap_v1/mmap_v1_extent_manager.h"
 #include "mongo/db/storage/record.h"
 #include "mongo/db/structure/catalog/namespace_details.h"
@@ -192,7 +191,7 @@ namespace mongo {
 
         CmdDropDatabase() : Command("dropDatabase") {}
 
-        bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             // disallow dropping the config database
             if (serverGlobalParams.configsvr && (dbname == "config")) {
                 errmsg = "Cannot drop 'config' database if mongod started with --configsvr";
@@ -211,17 +210,16 @@ namespace mongo {
                 // and that may need a global lock.
                 Lock::GlobalWrite lk;
                 Client::Context context(dbname);
-                DurTransaction txn;
 
                 log() << "dropDatabase " << dbname << " starting" << endl;
 
                 stopIndexBuilds(context.db(), cmdObj);
-                dropDatabase(&txn, context.db());
+                dropDatabase(txn, context.db());
 
                 log() << "dropDatabase " << dbname << " finished";
 
                 if (!fromRepl)
-                    logOp(&txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
+                    logOp(txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
             }
 
             result.append( "dropped" , dbname );
@@ -277,7 +275,7 @@ namespace mongo {
             return allKilledIndexes;
         }
 
-        bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             BSONElement e = cmdObj.firstElement();
             if ( e.numberInt() != 1 ) {
                 errmsg = "bad option";
@@ -288,7 +286,6 @@ namespace mongo {
             // called within, and that requires a global lock i believe.
             Lock::GlobalWrite lk;
             Client::Context context( dbname );
-            DurTransaction txn;
 
             log() << "repairDatabase " << dbname;
             std::vector<BSONObj> indexesInProg = stopIndexBuilds(context.db(), cmdObj);
@@ -298,7 +295,7 @@ namespace mongo {
             e = cmdObj.getField( "backupOriginalFiles" );
             bool backupOriginalFiles = e.isBoolean() && e.boolean();
             Status status =
-                repairDatabase( &txn, dbname, preserveClonedFilesOnFailure, backupOriginalFiles );
+                repairDatabase( txn, dbname, preserveClonedFilesOnFailure, backupOriginalFiles );
 
             IndexBuilder::restoreIndexes(indexesInProg);
 
@@ -354,13 +351,12 @@ namespace mongo {
 
         }
 
-        bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             // Needs to be locked exclusively, because creates the system.profile collection
             // in the local database.
             //
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(dbname);
-            DurTransaction txn;
 
             BSONElement e = cmdObj.firstElement();
             result.append("was", ctx.db()->getProfilingLevel());
@@ -372,7 +368,7 @@ namespace mongo {
             if ( p == -1 )
                 ok = true;
             else if ( p >= 0 && p <= 2 ) {
-                ok = ctx.db()->setProfilingLevel( &txn, p , errmsg );
+                ok = ctx.db()->setProfilingLevel( txn, p , errmsg );
             }
 
             BSONElement slow = cmdObj["slowms"];
@@ -452,7 +448,7 @@ namespace mongo {
             return IndexBuilder::killMatchingIndexBuilds(db->getCollection(nsToDrop), criteria);
         }
 
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
             const string nsToDrop = dbname + '.' + cmdObj.firstElement().valuestr();
             if (!serverGlobalParams.quiet) {
                 MONGO_TLOG(0) << "CMD: drop " << nsToDrop << endl;
@@ -465,10 +461,9 @@ namespace mongo {
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(nsToDrop);
-            DurTransaction txn;
             Database* db = ctx.db();
 
-            Collection* coll = db->getCollection( &txn, nsToDrop );
+            Collection* coll = db->getCollection( txn, nsToDrop );
             // If collection does not exist, short circuit and return.
             if ( !coll ) {
                 errmsg = "ns not found";
@@ -482,11 +477,11 @@ namespace mongo {
             result.append( "ns", nsToDrop );
             result.append( "nIndexesWas", numIndexes );
 
-            Status s = db->dropCollection( &txn, nsToDrop );
+            Status s = db->dropCollection( txn, nsToDrop );
 
             if ( s.isOK() ) {
                 if (!fromRepl)
-                    logOp(&txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
+                    logOp(txn, "c",(dbname + ".$cmd").c_str(), cmdObj);
                 return true;
             }
             
@@ -600,7 +595,7 @@ namespace mongo {
 
             return Status(ErrorCodes::Unauthorized, "unauthorized");
         }
-        virtual bool run(const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+        virtual bool newRun(TransactionExperiment* txn, const string& dbname , BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
             BSONObjIterator it(cmdObj);
 
             // Extract ns from first cmdObj element.
@@ -630,11 +625,10 @@ namespace mongo {
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx(ns);
-            DurTransaction txn;
 
             // Create collection.
             return appendCommandStatus( result,
-                                        userCreateNS(&txn, ctx.db(), ns.c_str(), options, !fromRepl) );
+                                        userCreateNS(txn, ctx.db(), ns.c_str(), options, !fromRepl) );
         }
     } cmdCreate;
 
@@ -1150,12 +1144,11 @@ namespace mongo {
             out->push_back(Privilege(parseResourcePattern(dbname, cmdObj), actions));
         }
 
-        bool run(const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
+        bool newRun(TransactionExperiment* txn, const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
             const string ns = dbname + "." + jsobj.firstElement().valuestr();
 
             Lock::DBWrite dbXLock(dbname);
             Client::Context ctx( ns );
-            DurTransaction txn;
 
             Collection* coll = ctx.db()->getCollection( ns );
             if ( !coll ) {
@@ -1181,9 +1174,9 @@ namespace mongo {
                         result.appendBool( "usePowerOf2Sizes_old", oldPowerOf2 );
 
                         if ( newPowerOf2 )
-                            coll->setUserFlag( &txn, NamespaceDetails::Flag_UsePowerOf2Sizes );
+                            coll->setUserFlag( txn, NamespaceDetails::Flag_UsePowerOf2Sizes );
                         else
-                            coll->clearUserFlag( &txn, NamespaceDetails::Flag_UsePowerOf2Sizes );
+                            coll->clearUserFlag( txn, NamespaceDetails::Flag_UsePowerOf2Sizes );
 
                         result.appendBool( "usePowerOf2Sizes_new", newPowerOf2 );
                     }
@@ -1232,7 +1225,7 @@ namespace mongo {
                     if ( oldExpireSecs != newExpireSecs ) {
                         // change expireAfterSeconds
                         result.appendAs( oldExpireSecs, "expireAfterSeconds_old" );
-                        coll->getIndexCatalog()->updateTTLSetting( &txn, idx, newExpireSecs.numberLong() );
+                        coll->getIndexCatalog()->updateTTLSetting( txn, idx, newExpireSecs.numberLong() );
                         result.appendAs( newExpireSecs , "expireAfterSeconds_new" );
                     }
                 }
@@ -1243,7 +1236,7 @@ namespace mongo {
             }
             
             if (ok && !fromRepl)
-                logOp(&txn, "c",(dbname + ".$cmd").c_str(), jsobj);
+                logOp(txn, "c",(dbname + ".$cmd").c_str(), jsobj);
 
             return ok;
         }
@@ -1394,7 +1387,8 @@ namespace mongo {
     } cmdWhatsMyUri;
 
 
-    bool _execCommand(Command *c,
+    bool _execCommand(TransactionExperiment* txn,
+                      Command *c,
                       const string& dbname,
                       BSONObj& cmdObj,
                       int queryOptions,
@@ -1403,7 +1397,7 @@ namespace mongo {
                       bool fromRepl) {
 
         try {
-            return c->run(dbname, cmdObj, queryOptions, errmsg, result, fromRepl);
+            return c->newRun(txn, dbname, cmdObj, queryOptions, errmsg, result, fromRepl);
         }
         catch ( SendStaleConfigException& e ){
             LOG(1) << "command failed because of stale config, can retry" << causedBy( e ) << endl;
@@ -1483,7 +1477,8 @@ namespace mongo {
      - context
      then calls run()
     */
-    void Command::execCommand(Command * c ,
+    void Command::execCommand(TransactionExperiment* txn,
+                              Command * c ,
                               Client& client,
                               int queryOptions,
                               const char *cmdns,
@@ -1585,7 +1580,7 @@ namespace mongo {
 
         client.curop()->ensureStarted();
 
-        retval = _execCommand(c, dbname, cmdObj, queryOptions, errmsg, result, fromRepl);
+        retval = _execCommand(txn, c, dbname, cmdObj, queryOptions, errmsg, result, fromRepl);
 
         appendCommandStatus(result, retval, errmsg);
         
@@ -1608,7 +1603,12 @@ namespace mongo {
 
        returns true if ran a cmd
     */
-    bool _runCommands(const char *ns, BSONObj& _cmdobj, BufBuilder &b, BSONObjBuilder& anObjBuilder, bool fromRepl, int queryOptions) {
+    bool _runCommands(TransactionExperiment* txn,
+                      const char* ns,
+                      BSONObj& _cmdobj,
+                      BufBuilder& b,
+                      BSONObjBuilder& anObjBuilder,
+                      bool fromRepl, int queryOptions) {
         string dbname = nsToDatabase( ns );
 
         LOG(2) << "run command " << ns << ' ' << _cmdobj << endl;
@@ -1654,7 +1654,7 @@ namespace mongo {
         Command * c = e.type() ? Command::findCommand( e.fieldName() ) : 0;
 
         if ( c ) {
-            Command::execCommand(c, client, queryOptions, ns, jsobj, anObjBuilder, fromRepl);
+            Command::execCommand(txn, c, client, queryOptions, ns, jsobj, anObjBuilder, fromRepl);
         }
         else {
             Command::appendCommandStatus(anObjBuilder,
diff --git a/src/mongo/db/dbhelpers.cpp b/src/mongo/db/dbhelpers.cpp
index 38815864034..72d60dffbcd 100644
--- a/src/mongo/db/dbhelpers.cpp
+++ b/src/mongo/db/dbhelpers.cpp
@@ -318,7 +318,8 @@ namespace mongo {
         return true;
     }
 
-    long long Helpers::removeRange( const KeyRange& range,
+    long long Helpers::removeRange( TransactionExperiment* txn,
+                                    const KeyRange& range,
                                     bool maxInclusive,
                                     bool secondaryThrottle,
                                     RemoveSaver* callback,
@@ -366,8 +367,7 @@ namespace mongo {
             // Scoping for write lock.
             {
                 Client::WriteContext ctx(ns);
-                DurTransaction txn;
-                Collection* collection = ctx.ctx().db()->getCollection( &txn, ns );
+                Collection* collection = ctx.ctx().db()->getCollection( txn, ns );
                 if ( !collection )
                     break;
 
@@ -437,8 +437,8 @@ namespace mongo {
                 if ( callback )
                     callback->goingToDelete( obj );
 
-                logOp(&txn, "d", ns.c_str(), obj["_id"].wrap(), 0, 0, fromMigrate);
-                collection->deleteDocument( &txn, rloc );
+                logOp(txn, "d", ns.c_str(), obj["_id"].wrap(), 0, 0, fromMigrate);
+                collection->deleteDocument( txn, rloc );
                 numDeleted++;
             }
 
diff --git a/src/mongo/db/dbhelpers.h b/src/mongo/db/dbhelpers.h
index 660ef27f926..c10c6f24a21 100644
--- a/src/mongo/db/dbhelpers.h
+++ b/src/mongo/db/dbhelpers.h
@@ -162,7 +162,8 @@ namespace mongo {
          * Does oplog the individual document deletions.
          * // TODO: Refactor this mechanism, it is growing too large
          */
-        static long long removeRange( const KeyRange& range,
+        static long long removeRange( TransactionExperiment* txn,
+                                      const KeyRange& range,
                                       bool maxInclusive = false,
                                       bool secondaryThrottle = false,
                                       RemoveSaver* callback = NULL,
diff --git a/src/mongo/db/dbwebserver.cpp b/src/mongo/db/dbwebserver.cpp
index cfd6c747e38..e63ad58f0d8 100644
--- a/src/mongo/db/dbwebserver.cpp
+++ b/src/mongo/db/dbwebserver.cpp
@@ -50,6 +50,7 @@
 #include "mongo/db/db.h"
 #include "mongo/db/instance.h"
 #include "mongo/db/stats/snapshots.h"
+#include "mongo/db/storage/mmap_v1/dur_transaction.h"
 #include "mongo/util/admin_access.h"
 #include "mongo/util/md5.hpp"
 #include "mongo/util/mongoutils/html.h"
@@ -73,13 +74,20 @@ namespace mongo {
 
     class DbWebServer : public MiniWebServer {
     public:
-        DbWebServer(const string& ip, int port, const AdminAccess* webUsers)
-            : MiniWebServer("admin web console", ip, port), _webUsers(webUsers) {
+        DbWebServer(const string& ip,
+                    int port,
+                    const AdminAccess* webUsers,
+                    TransactionExperiment::Factory transactionFactory)
+                : MiniWebServer("admin web console", ip, port),
+                  _webUsers(webUsers),
+                  _transactionFactory(transactionFactory) {
+
             WebStatusPlugin::initAll();
         }
 
     private:
         const AdminAccess* _webUsers; // not owned here
+        const TransactionExperiment::Factory _transactionFactory;
 
         void doUnlockedStuff(stringstream& ss) {
             /* this is in the header already ss << "port:      " << port << '\n'; */
@@ -179,6 +187,9 @@ namespace mongo {
             vector<string>& headers, // if completely empty, content-type: text/html will be added
             const SockAddr &from
         ) {
+
+            boost::scoped_ptr<TransactionExperiment> txn(_transactionFactory()); // XXX SERVER-13931
+
             if ( url.size() > 1 ) {
 
                 if ( ! allowed( rq , headers, from ) ) {
@@ -206,7 +217,7 @@ namespace mongo {
                             uassert(13453, "server not started with --jsonp",
                                     callback.empty() || serverGlobalParams.jsonp);
 
-                            handler->handle( rq , url , params , responseMsg , responseCode , headers , from );
+                            handler->handle( txn.get(), rq , url , params , responseMsg , responseCode , headers , from );
 
                             if (responseCode == 200 && !callback.empty()) {
                                 responseMsg = callback + '(' + responseMsg + ')';
@@ -410,7 +421,8 @@ namespace mongo {
     public:
         FavIconHandler() : DbWebHandler( "favicon.ico" , 0 , false ) {}
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
             responseCode = 404;
@@ -424,7 +436,8 @@ namespace mongo {
     public:
         StatusHandler() : DbWebHandler( "_status" , 1 , false ) {}
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
             headers.push_back( "Content-Type: application/json;charset=utf-8" );
@@ -459,7 +472,7 @@ namespace mongo {
                 string errmsg;
 
                 BSONObjBuilder sub;
-                if ( ! c->run( "admin.$cmd" , co , 0, errmsg , sub , false ) )
+                if ( ! c->newRun( txn, "admin.$cmd" , co , 0, errmsg , sub , false ) )
                     buf.append( cmd , errmsg );
                 else
                     buf.append( cmd , sub.obj() );
@@ -475,7 +488,8 @@ namespace mongo {
     public:
         CommandListHandler() : DbWebHandler( "_commands" , 1 , true ) {}
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
             headers.push_back( "Content-Type: text/html;charset=utf-8" );
@@ -527,7 +541,8 @@ namespace mongo {
             return _cmd(cmd) != 0;
         }
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
             string cmd;
@@ -540,7 +555,7 @@ namespace mongo {
             Client& client = cc();
 
             BSONObjBuilder result;
-            Command::execCommand(c, client, 0, "admin.", cmdObj , result, false);
+            Command::execCommand(txn, c, client, 0, "admin.", cmdObj , result, false);
 
             responseCode = 200;
 
@@ -561,11 +576,12 @@ namespace mongo {
 
     // --- external ----
 
-    void webServerThread(const AdminAccess* adminAccess) {
+    void webServerThread(const AdminAccess* adminAccess,
+                         TransactionExperiment::Factory transactionFactory) {
         boost::scoped_ptr<const AdminAccess> adminAccessPtr(adminAccess); // adminAccess is owned here
         Client::initThread("websvr");
         const int p = serverGlobalParams.port + 1000;
-        DbWebServer mini(serverGlobalParams.bind_ip, p, adminAccessPtr.get());
+        DbWebServer mini(serverGlobalParams.bind_ip, p, adminAccessPtr.get(), transactionFactory);
         mini.setupSockets();
         mini.initAndListen();
         cc().shutdown();
diff --git a/src/mongo/db/dbwebserver.h b/src/mongo/db/dbwebserver.h
index 894ad574baf..445f3f2ef33 100644
--- a/src/mongo/db/dbwebserver.h
+++ b/src/mongo/db/dbwebserver.h
@@ -34,6 +34,7 @@
 
 #include "mongo/util/admin_access.h"
 #include "mongo/util/net/sock.h"
+#include "mongo/db/storage/transaction.h"
 
 namespace mongo {
 
@@ -54,7 +55,8 @@ namespace mongo {
 
         virtual bool requiresREST( const string& url ) const { return _requiresREST; }
 
-        virtual void handle( const char *rq, // the full request
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, // the full request
                              const std::string& url,
                              BSONObj params,
                              // set these and return them:
@@ -94,8 +96,7 @@ namespace mongo {
         static vector<WebStatusPlugin*> * _plugins;
 
     };
-
-    void webServerThread( const AdminAccess* admins );
+    void webServerThread( const AdminAccess* admins, TransactionExperiment::Factory transactionFactory );
     string prettyHostName();
 
 };
diff --git a/src/mongo/db/instance.cpp b/src/mongo/db/instance.cpp
index 4db14c1d689..ab711aab742 100644
--- a/src/mongo/db/instance.cpp
+++ b/src/mongo/db/instance.cpp
@@ -96,11 +96,11 @@ namespace mongo {
     inline void opread(Message& m) { if( _diaglog.getLevel() & 2 ) _diaglog.readop((char *) m.singleData(), m.header()->len); }
     inline void opwrite(Message& m) { if( _diaglog.getLevel() & 1 ) _diaglog.writeop((char *) m.singleData(), m.header()->len); }
 
-    void receivedKillCursors(Message& m);
-    void receivedUpdate(Message& m, CurOp& op);
-    void receivedDelete(Message& m, CurOp& op);
-    void receivedInsert(Message& m, CurOp& op);
-    bool receivedGetMore(DbResponse& dbresponse, Message& m, CurOp& curop );
+    void receivedKillCursors(TransactionExperiment* txn, Message& m);
+    void receivedUpdate(TransactionExperiment* txn, Message& m, CurOp& op);
+    void receivedDelete(TransactionExperiment* txn, Message& m, CurOp& op);
+    void receivedInsert(TransactionExperiment* txn, Message& m, CurOp& op);
+    bool receivedGetMore(TransactionExperiment* txn, DbResponse& dbresponse, Message& m, CurOp& curop );
 
     int nloggedsome = 0;
 #define LOGWITHRATELIMIT if( ++nloggedsome < 1000 || nloggedsome % 100 == 0 )
@@ -232,7 +232,7 @@ namespace mongo {
         replyToQuery(0, m, dbresponse, obj);
     }
 
-    static bool receivedQuery(Client& c, DbResponse& dbresponse, Message& m ) {
+    static bool receivedQuery(TransactionExperiment* txn, Client& c, DbResponse& dbresponse, Message& m ) {
         bool ok = true;
         MSGID responseTo = m.header()->id;
 
@@ -253,7 +253,7 @@ namespace mongo {
                 audit::logQueryAuthzCheck(client, ns, q.query, status.code());
                 uassertStatusOK(status);
             }
-            dbresponse.exhaustNS = newRunQuery(m, q, op, *resp);
+            dbresponse.exhaustNS = newRunQuery(txn, m, q, op, *resp);
             verify( !resp->empty() );
         }
         catch ( SendStaleConfigException& e ){
@@ -329,7 +329,10 @@ namespace mongo {
     }
 
     // Returns false when request includes 'end'
-    void assembleResponse( Message &m, DbResponse &dbresponse, const HostAndPort& remote ) {
+    void assembleResponse( TransactionExperiment* txn,
+                           Message& m,
+                           DbResponse& dbresponse,
+                           const HostAndPort& remote ) {
 
         // before we lock...
         int op = m.operation();
@@ -418,10 +421,10 @@ namespace mongo {
         if ( op == dbQuery ) {
             if ( handlePossibleShardedMessage( m , &dbresponse ) )
                 return;
-            receivedQuery(c , dbresponse, m );
+            receivedQuery(txn, c , dbresponse, m );
         }
         else if ( op == dbGetMore ) {
-            if ( ! receivedGetMore(dbresponse, m, currentOp) )
+            if ( ! receivedGetMore(txn, dbresponse, m, currentOp) )
                 shouldLog = true;
         }
         else if ( op == dbMsg ) {
@@ -451,20 +454,20 @@ namespace mongo {
                 if ( op == dbKillCursors ) {
                     currentOp.ensureStarted();
                     logThreshold = 10;
-                    receivedKillCursors(m);
+                    receivedKillCursors(txn, m);
                 }
                 else if ( !nsString.isValid() ) {
                     // Only killCursors doesn't care about namespaces
                     uassert( 16257, str::stream() << "Invalid ns [" << ns << "]", false );
                 }
                 else if ( op == dbInsert ) {
-                    receivedInsert(m, currentOp);
+                    receivedInsert(txn, m, currentOp);
                 }
                 else if ( op == dbUpdate ) {
-                    receivedUpdate(m, currentOp);
+                    receivedUpdate(txn, m, currentOp);
                 }
                 else if ( op == dbDelete ) {
-                    receivedDelete(m, currentOp);
+                    receivedDelete(txn, m, currentOp);
                 }
                 else {
                     mongo::log() << "    operation isn't supported: " << op << endl;
@@ -503,8 +506,7 @@ namespace mongo {
                 LOG(1) << "note: not profiling because doing fsync+lock" << endl;
             }
             else {
-                DurTransaction txn;
-                profile(&txn, c, op, currentOp);
+                profile(txn, c, op, currentOp);
             }
         }
 
@@ -512,7 +514,7 @@ namespace mongo {
         debug.reset();
     } /* assembleResponse() */
 
-    void receivedKillCursors(Message& m) {
+    void receivedKillCursors(TransactionExperiment* txn, Message& m) {
         int *x = (int *) m.singleData()->_data;
         x++; // reserved
         int n = *x++;
@@ -561,7 +563,7 @@ namespace mongo {
         delete database; // closes files
     }
 
-    void receivedUpdate(Message& m, CurOp& op) {
+    void receivedUpdate(TransactionExperiment* txn, Message& m, CurOp& op) {
         DbMessage d(m);
         NamespaceString ns(d.getns());
         uassertStatusOK( userAllowedWriteNS( ns ) );
@@ -609,15 +611,14 @@ namespace mongo {
             return;
 
         Client::Context ctx( ns );
-        DurTransaction txn;
 
-        UpdateResult res = executor.execute(&txn, ctx.db());
+        UpdateResult res = executor.execute(txn, ctx.db());
 
         // for getlasterror
         lastError.getSafe()->recordUpdate( res.existing , res.numMatched , res.upserted );
     }
 
-    void receivedDelete(Message& m, CurOp& op) {
+    void receivedDelete(TransactionExperiment* txn, Message& m, CurOp& op) {
         DbMessage d(m);
         NamespaceString ns(d.getns());
         uassertStatusOK( userAllowedWriteNS( ns ) );
@@ -649,16 +650,15 @@ namespace mongo {
             return;
 
         Client::Context ctx(ns);
-        DurTransaction txn;
 
-        long long n = executor.execute(&txn, ctx.db());
+        long long n = executor.execute(txn, ctx.db());
         lastError.getSafe()->recordDelete( n );
         op.debug().ndeleted = n;
     }
 
     QueryResult* emptyMoreResult(long long);
 
-    bool receivedGetMore(DbResponse& dbresponse, Message& m, CurOp& curop ) {
+    bool receivedGetMore(TransactionExperiment* txn, DbResponse& dbresponse, Message& m, CurOp& curop ) {
         bool ok = true;
 
         DbMessage d(m);
@@ -854,7 +854,7 @@ namespace mongo {
         op.debug().ninserted = i;
     }
 
-    void receivedInsert(Message& m, CurOp& op) {
+    void receivedInsert(TransactionExperiment* txn, Message& m, CurOp& op) {
         DbMessage d(m);
         const char *ns = d.getns();
         op.debug().ns = ns;
@@ -889,13 +889,12 @@ namespace mongo {
             return;
 
         Client::Context ctx(ns);
-        DurTransaction txn;
 
         if (multi.size() > 1) {
             const bool keepGoing = d.reservedField() & InsertOption_ContinueOnError;
-            insertMulti(&txn, ctx, keepGoing, ns, multi, op);
+            insertMulti(txn, ctx, keepGoing, ns, multi, op);
         } else {
-            checkAndInsert(&txn, ctx, ns, multi[0]);
+            checkAndInsert(txn, ctx, ns, multi[0]);
             globalOpCounters.incInsertInWriteLock(1);
             op.debug().ninserted = 1;
         }
@@ -942,6 +941,15 @@ namespace mongo {
         return false;
     }
 
+    DBDirectClient::DBDirectClient() 
+        : _txnOwned(new DurTransaction),
+          _txn(_txnOwned.get())
+    {}
+
+    DBDirectClient::DBDirectClient(TransactionExperiment* txn) 
+        : _txn(txn)
+    {}
+
     QueryOptions DBDirectClient::_lookupAvailableOptions() {
         // Exhaust mode is not available in DBDirectClient.
         return QueryOptions(DBClientBase::_lookupAvailableOptions() & ~QueryOption_Exhaust);
@@ -965,11 +973,11 @@ namespace {
         if ( lastError._get() )
             lastError.startRequest( toSend, lastError._get() );
         DbResponse dbResponse;
-        assembleResponse( toSend, dbResponse , _clientHost );
+        assembleResponse( _txn, toSend, dbResponse , _clientHost );
         verify( dbResponse.response );
         dbResponse.response->concat(); // can get rid of this if we make response handling smarter
         response = *dbResponse.response;
-        getDur().commitIfNeeded();
+        _txn->commitIfNeeded();
         return true;
     }
 
@@ -978,8 +986,8 @@ namespace {
         if ( lastError._get() )
             lastError.startRequest( toSend, lastError._get() );
         DbResponse dbResponse;
-        assembleResponse( toSend, dbResponse , _clientHost );
-        getDur().commitIfNeeded();
+        assembleResponse( _txn, toSend, dbResponse , _clientHost );
+        _txn->commitIfNeeded();
     }
 
     auto_ptr<DBClientCursor> DBDirectClient::query(const string &ns, Query query, int nToReturn , int nToSkip ,
diff --git a/src/mongo/db/instance.h b/src/mongo/db/instance.h
index d848f6f1c09..50a988917ad 100644
--- a/src/mongo/db/instance.h
+++ b/src/mongo/db/instance.h
@@ -35,6 +35,7 @@
 #include "mongo/db/client.h"
 #include "mongo/db/curop-inl.h"
 #include "mongo/db/dbmessage.h"
+#include "mongo/db/storage/transaction.h"
 #include "mongo/db/storage_options.h"
 
 namespace mongo {
@@ -67,7 +68,10 @@ namespace mongo {
 
     extern DiagLog _diaglog;
 
-    void assembleResponse( Message &m, DbResponse &dbresponse, const HostAndPort &client );
+    void assembleResponse( TransactionExperiment* txn,
+                           Message& m,
+                           DbResponse& dbresponse,
+                           const HostAndPort &client );
 
     void getDatabaseNames(vector<std::string> &names,
                           const std::string& usePath = storageGlobalParams.dbpath);
@@ -82,6 +86,9 @@ namespace mongo {
      */
     class DBDirectClient : public DBClientBase {
     public:
+        DBDirectClient(); // DEPRECATED
+        DBDirectClient(TransactionExperiment* txn); // txn must outlive this object
+
         using DBClientBase::query;
 
         virtual auto_ptr<DBClientCursor> query(const string &ns, Query query, int nToReturn = 0, int nToSkip = 0,
@@ -126,6 +133,8 @@ namespace mongo {
 
     private:
         static HostAndPort _clientHost;
+        boost::scoped_ptr<TransactionExperiment> _txnOwned;
+        TransactionExperiment* _txn; // Points either to _txnOwned or a passed-in transaction.
     };
 
     extern int lockFile;
diff --git a/src/mongo/db/query/new_find.cpp b/src/mongo/db/query/new_find.cpp
index 40990a0baa6..9236cb92333 100644
--- a/src/mongo/db/query/new_find.cpp
+++ b/src/mongo/db/query/new_find.cpp
@@ -109,7 +109,8 @@ namespace {
 namespace mongo {
 
     // TODO: Move this and the other command stuff in newRunQuery outta here and up a level.
-    static bool runCommands(const char *ns,
+    static bool runCommands(TransactionExperiment* txn,
+                            const char *ns,
                             BSONObj& jsobj,
                             CurOp& curop,
                             BufBuilder &b,
@@ -117,7 +118,7 @@ namespace mongo {
                             bool fromRepl,
                             int queryOptions) {
         try {
-            return _runCommands(ns, jsobj, b, anObjBuilder, fromRepl, queryOptions);
+            return _runCommands(txn, ns, jsobj, b, anObjBuilder, fromRepl, queryOptions);
         }
         catch( SendStaleConfigException& ){
             throw;
@@ -397,7 +398,11 @@ namespace mongo {
         return Status::OK();
     }
 
-    std::string newRunQuery(Message& m, QueryMessage& q, CurOp& curop, Message &result) {
+    std::string newRunQuery(TransactionExperiment* txn,
+                            Message& m,
+                            QueryMessage& q,
+                            CurOp& curop,
+                            Message &result) {
         // Validate the namespace.
         const char *ns = q.ns;
         uassert(16332, "can't have an empty ns", ns[0]);
@@ -424,7 +429,7 @@ namespace mongo {
             bb.skip(sizeof(QueryResult));
 
             BSONObjBuilder cmdResBuf;
-            if (!runCommands(ns, q.query, curop, bb, cmdResBuf, false, q.queryOptions)) {
+            if (!runCommands(txn, ns, q.query, curop, bb, cmdResBuf, false, q.queryOptions)) {
                 uasserted(13530, "bad or malformed command request?");
             }
 
diff --git a/src/mongo/db/query/new_find.h b/src/mongo/db/query/new_find.h
index 2977a83ab51..149bcce9b0a 100644
--- a/src/mongo/db/query/new_find.h
+++ b/src/mongo/db/query/new_find.h
@@ -39,6 +39,8 @@
 
 namespace mongo {
 
+    class TransactionExperiment;
+
     /**
      * Called from the getMore entry point in ops/query.cpp.
      */
@@ -48,6 +50,10 @@ namespace mongo {
     /**
      * Run the query 'q' and place the result in 'result'.
      */
-    std::string newRunQuery(Message& m, QueryMessage& q, CurOp& curop, Message &result);
+    std::string newRunQuery(TransactionExperiment* txn,
+                            Message& m,
+                            QueryMessage& q,
+                            CurOp& curop,
+                            Message &result);
 
 }  // namespace mongo
diff --git a/src/mongo/db/range_deleter.cpp b/src/mongo/db/range_deleter.cpp
index 0ea7e44e4ec..229f7e82060 100644
--- a/src/mongo/db/range_deleter.cpp
+++ b/src/mongo/db/range_deleter.cpp
@@ -73,7 +73,8 @@ namespace mongo {
     struct RangeDeleter::RangeDeleteEntry {
         RangeDeleteEntry():
                 secondaryThrottle(true),
-                notifyDone(NULL) {
+                notifyDone(NULL),
+                transactionFactory(TransactionExperiment::factoryNULL) { // XXX SERVER-13931
         }
 
         std::string ns;
@@ -99,6 +100,8 @@ namespace mongo {
         // Important invariant: Can only be set and used by one thread.
         Notification* notifyDone;
 
+        TransactionExperiment::Factory transactionFactory;
+
         // For debugging only
         BSONObj toBSON() const {
             return BSON("ns" << ns
@@ -193,7 +196,8 @@ namespace mongo {
         }
     }
 
-    bool RangeDeleter::queueDelete(const std::string& ns,
+    bool RangeDeleter::queueDelete(TransactionExperiment::Factory transactionFactory,
+                                   const std::string& ns,
                                    const BSONObj& min,
                                    const BSONObj& max,
                                    const BSONObj& shardKeyPattern,
@@ -204,6 +208,7 @@ namespace mongo {
         if (errMsg == NULL) errMsg = &dummy;
 
         auto_ptr<RangeDeleteEntry> toDelete(new RangeDeleteEntry);
+        toDelete->transactionFactory = transactionFactory;
         toDelete->ns = ns;
         toDelete->min = min.getOwned();
         toDelete->max = max.getOwned();
@@ -247,7 +252,8 @@ namespace mongo {
         return true;
     }
 
-    bool RangeDeleter::deleteNow(const std::string& ns,
+    bool RangeDeleter::deleteNow(TransactionExperiment* txn,
+                                 const std::string& ns,
                                  const BSONObj& min,
                                  const BSONObj& max,
                                  const BSONObj& shardKeyPattern,
@@ -323,7 +329,7 @@ namespace mongo {
             sleepmillis(checkIntervalMillis);
         }
 
-        bool result = _env->deleteRange(ns, min, max, shardKeyPattern,
+        bool result = _env->deleteRange(txn, ns, min, max, shardKeyPattern,
                                         secondaryThrottle, errMsg);
 
         {
@@ -468,14 +474,18 @@ namespace mongo {
                 _stats->incInProgressDeletes_inlock();
             }
 
-            if (!_env->deleteRange(nextTask->ns,
-                                   nextTask->min,
-                                   nextTask->max,
-                                   nextTask->shardKeyPattern,
-                                   nextTask->secondaryThrottle,
-                                   &errMsg)) {
-                warning() << "Error encountered while trying to delete range: "
-                          << errMsg << endl;
+            {
+                boost::scoped_ptr<TransactionExperiment> txn(nextTask->transactionFactory()); // XXX SERVER-13931
+                if (!_env->deleteRange(txn.get(),
+                                       nextTask->ns,
+                                       nextTask->min,
+                                       nextTask->max,
+                                       nextTask->shardKeyPattern,
+                                       nextTask->secondaryThrottle,
+                                       &errMsg)) {
+                    warning() << "Error encountered while trying to delete range: "
+                              << errMsg << endl;
+                }
             }
 
             {
diff --git a/src/mongo/db/range_deleter.h b/src/mongo/db/range_deleter.h
index b8fd0789c5a..653fb0105b0 100644
--- a/src/mongo/db/range_deleter.h
+++ b/src/mongo/db/range_deleter.h
@@ -37,6 +37,7 @@
 #include "mongo/base/string_data.h"
 #include "mongo/db/clientcursor.h"
 #include "mongo/db/jsobj.h"
+#include "mongo/db/storage/transaction.h"
 #include "mongo/util/concurrency/mutex.h"
 #include "mongo/util/concurrency/synchronization.h"
 
@@ -44,6 +45,7 @@ namespace mongo {
 
     struct RangeDeleterEnv;
     class RangeDeleterStats;
+    class TransactionExperiment;
 
     /**
      * Class for deleting documents for a given namespace and range.  It contains a queue of
@@ -129,7 +131,8 @@ namespace mongo {
          * Returns true if the task is queued and false If the given range is blacklisted,
          * is already queued, or stopWorkers() was called.
          */
-        bool queueDelete(const std::string& ns,
+        bool queueDelete(TransactionExperiment::Factory transactionFactory,
+                         const std::string& ns,
                          const BSONObj& min,
                          const BSONObj& max,
                          const BSONObj& shardKeyPattern,
@@ -144,7 +147,8 @@ namespace mongo {
          * Returns true if the deletion was performed. False if the range is blacklisted,
          * was already queued, or stopWorkers() was called.
          */
-        bool deleteNow(const std::string& ns,
+        bool deleteNow(TransactionExperiment* txn,
+                       const std::string& ns,
                        const BSONObj& min,
                        const BSONObj& max,
                        const BSONObj& shardKeyPattern,
@@ -284,7 +288,8 @@ namespace mongo {
          * Must be a synchronous call. Docs should be deleted after call ends.
          * Must not throw Exceptions.
          */
-        virtual bool deleteRange(const StringData& ns,
+        virtual bool deleteRange(TransactionExperiment* txn,
+                                 const StringData& ns,
                                  const BSONObj& inclusiveLower,
                                  const BSONObj& exclusiveUpper,
                                  const BSONObj& shardKeyPattern,
diff --git a/src/mongo/db/range_deleter_db_env.cpp b/src/mongo/db/range_deleter_db_env.cpp
index 3d2f61c221c..71a0ca86796 100644
--- a/src/mongo/db/range_deleter_db_env.cpp
+++ b/src/mongo/db/range_deleter_db_env.cpp
@@ -54,7 +54,8 @@ namespace mongo {
      * 5. Delete range.
      * 6. Wait until the majority of the secondaries catch up.
      */
-    bool RangeDeleterDBEnv::deleteRange(const StringData& ns,
+    bool RangeDeleterDBEnv::deleteRange(TransactionExperiment* txn,
+                                        const StringData& ns,
                                         const BSONObj& inclusiveLower,
                                         const BSONObj& exclusiveUpper,
                                         const BSONObj& keyPattern,
@@ -80,7 +81,8 @@ namespace mongo {
 
             try {
                 long long numDeleted =
-                        Helpers::removeRange(KeyRange(ns.toString(),
+                        Helpers::removeRange(txn,
+                                             KeyRange(ns.toString(),
                                                       inclusiveLower,
                                                       exclusiveUpper,
                                                       keyPattern),
diff --git a/src/mongo/db/range_deleter_db_env.h b/src/mongo/db/range_deleter_db_env.h
index b55389e3edd..01089fc9d3d 100644
--- a/src/mongo/db/range_deleter_db_env.h
+++ b/src/mongo/db/range_deleter_db_env.h
@@ -51,7 +51,8 @@ namespace mongo {
          *
          * Does not throw Exceptions.
          */
-        virtual bool deleteRange(const StringData& ns,
+        virtual bool deleteRange(TransactionExperiment* txn,
+                                 const StringData& ns,
                                  const BSONObj& inclusiveLower,
                                  const BSONObj& exclusiveUpper,
                                  const BSONObj& keyPattern,
diff --git a/src/mongo/db/range_deleter_mock_env.cpp b/src/mongo/db/range_deleter_mock_env.cpp
index 536d463417e..22ecff1bea4 100644
--- a/src/mongo/db/range_deleter_mock_env.cpp
+++ b/src/mongo/db/range_deleter_mock_env.cpp
@@ -100,7 +100,8 @@ namespace mongo {
         return _deleteList.back();
     }
 
-    bool RangeDeleterMockEnv::deleteRange(const StringData& ns,
+    bool RangeDeleterMockEnv::deleteRange(TransactionExperiment* txn,
+                                          const StringData& ns,
                                           const BSONObj& min,
                                           const BSONObj& max,
                                           const BSONObj& shardKeyPattern,
diff --git a/src/mongo/db/range_deleter_mock_env.h b/src/mongo/db/range_deleter_mock_env.h
index 7b1cd3932e3..4ba3e686d9d 100644
--- a/src/mongo/db/range_deleter_mock_env.h
+++ b/src/mongo/db/range_deleter_mock_env.h
@@ -126,7 +126,8 @@ namespace mongo {
          * but simply keeps a record of it. Can also be paused by pauseDeletes and
          * resumed with resumeDeletes.
          */
-        bool deleteRange(const StringData& ns,
+        bool deleteRange(TransactionExperiment* txn,
+                         const StringData& ns,
                          const BSONObj& min,
                          const BSONObj& max,
                          const BSONObj& shardKeyPattern,
diff --git a/src/mongo/db/range_deleter_stat_test.cpp b/src/mongo/db/range_deleter_stat_test.cpp
index 6de5f15d196..695da1d8a26 100644
--- a/src/mongo/db/range_deleter_stat_test.cpp
+++ b/src/mongo/db/range_deleter_stat_test.cpp
@@ -48,6 +48,9 @@ namespace {
     using mongo::RangeDeleter;
     using mongo::RangeDeleterMockEnv;
     using mongo::RangeDeleterStats;
+    using mongo::TransactionExperiment;
+
+    TransactionExperiment* const noTxn = NULL; // MockEnv doesn't need txn XXX SERVER-13931
 
     TEST(NoDeletes, InitialState) {
         RangeDeleterMockEnv* env = new RangeDeleterMockEnv();
@@ -85,7 +88,8 @@ namespace {
 
         string errMsg;
         Notification notifyDone;
-        ASSERT_TRUE(deleter.queueDelete(ns,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL,
+                                        ns,
                                         BSON("x" << 0),
                                         BSON("x" << 10),
                                         BSON("x" << 1),
@@ -127,7 +131,8 @@ namespace {
 
         Notification deleteDone;
         string errMsg;
-        ASSERT_TRUE(deleter.queueDelete(ns,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns,
                                         BSON("x" << 0),
                                         BSON("x" << 10),
                                         BSON("x" << 1),
@@ -170,7 +175,8 @@ namespace {
 
         string errMsg;
         Notification notifyDone;
-        ASSERT_TRUE(deleter.queueDelete(ns,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns,
                                         BSON("x" << 0),
                                         BSON("x" << 10),
                                         BSON("x" << 1),
@@ -213,6 +219,7 @@ namespace {
         string errMsg;
         boost::thread deleterThread = boost::thread(boost::bind(&RangeDeleter::deleteNow,
                                                                 &deleter,
+                                                                noTxn,
                                                                 ns,
                                                                 BSON("x" << 0),
                                                                 BSON("x" << 10),
@@ -256,6 +263,7 @@ namespace {
         string errMsg;
         boost::thread deleterThread = boost::thread(boost::bind(&RangeDeleter::deleteNow,
                                                                 &deleter,
+                                                                noTxn,
                                                                 ns,
                                                                 BSON("x" << 0),
                                                                 BSON("x" << 10),
@@ -296,7 +304,7 @@ namespace {
 
         const string ns("test.user");
         string errMsg;
-        ASSERT_TRUE(deleter.deleteNow(ns, BSON("x" << 0), BSON("x" << 10),
+        ASSERT_TRUE(deleter.deleteNow(noTxn, ns, BSON("x" << 0), BSON("x" << 10),
                                       BSON("x" << 1), true, &errMsg));
 
         const BSONObj stats(deleter.getStats()->toBSON());
diff --git a/src/mongo/db/range_deleter_test.cpp b/src/mongo/db/range_deleter_test.cpp
index 23a93da14b0..1bc2ac0beae 100644
--- a/src/mongo/db/range_deleter_test.cpp
+++ b/src/mongo/db/range_deleter_test.cpp
@@ -49,6 +49,9 @@ namespace {
     using mongo::RangeDeleter;
     using mongo::RangeDeleterMockEnv;
     using mongo::RangeDeleterStats;
+    using mongo::TransactionExperiment;
+
+    TransactionExperiment* const noTxn = NULL; // MockEnv doesn't need txn XXX SERVER-13931
 
     // Capped sleep interval is 640 mSec, Nyquist frequency is 1280 mSec => round up to 2 sec.
     const int MAX_IMMEDIATE_DELETE_WAIT_SECS = 2;
@@ -62,7 +65,8 @@ namespace {
         deleter.stopWorkers();
 
         string errMsg;
-        ASSERT_FALSE(deleter.queueDelete("test.user",
+        ASSERT_FALSE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                         "test.user",
                                          BSON("x" << 120),
                                          BSON("x" << 200),
                                          BSON("x" << 1),
@@ -84,7 +88,8 @@ namespace {
         env->addCursorId(ns, 345);
 
         Notification notifyDone;
-        ASSERT_TRUE(deleter.queueDelete(ns, BSON("x" << 0), BSON("x" << 10), BSON("x" << 1),
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns, BSON("x" << 0), BSON("x" << 10), BSON("x" << 1),
                                         true, &notifyDone, NULL /* errMsg not needed */));
 
         env->waitForNthGetCursor(1u);
@@ -122,7 +127,8 @@ namespace {
         env->addCursorId(ns, 345);
 
         Notification notifyDone;
-        ASSERT_TRUE(deleter.queueDelete(ns, BSON("x" << 0), BSON("x" << 10),  BSON("x" << 1),
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns, BSON("x" << 0), BSON("x" << 10),  BSON("x" << 1),
                                         true, &notifyDone, NULL /* errMsg not needed */));
 
 
@@ -145,6 +151,7 @@ namespace {
         string errMsg;
         boost::thread deleterThread = boost::thread(boost::bind(&RangeDeleter::deleteNow,
                                                                 &deleter,
+                                                                noTxn,
                                                                 ns,
                                                                 BSON("x" << 0),
                                                                 BSON("x" << 10),
@@ -194,6 +201,7 @@ namespace {
         string errMsg;
         boost::thread deleterThread = boost::thread(boost::bind(&RangeDeleter::deleteNow,
                                                                 &deleter,
+                                                                noTxn,
                                                                 ns,
                                                                 BSON("x" << 0),
                                                                 BSON("x" << 10),
@@ -238,7 +246,8 @@ namespace {
         env->pauseDeletes();
 
         Notification notifyDone1;
-        ASSERT_TRUE(deleter.queueDelete(ns,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns,
                                         BSON("x" << 10),
                                         BSON("x" << 20),
                                         BSON("x" << 1),
@@ -256,7 +265,8 @@ namespace {
         ASSERT_EQUALS(1, inProgressCount);
 
         Notification notifyDone2;
-        ASSERT_TRUE(deleter.queueDelete(blockedNS,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        blockedNS,
                                         BSON("x" << 20),
                                         BSON("x" << 30),
                                         BSON("x" << 1),
@@ -265,7 +275,8 @@ namespace {
                                         NULL /* don't care errMsg */));
 
         Notification notifyDone3;
-        ASSERT_TRUE(deleter.queueDelete(ns,
+        ASSERT_TRUE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                        ns,
                                         BSON("x" << 30),
                                         BSON("x" << 40),
                                         BSON("x" << 1),
@@ -352,12 +363,13 @@ namespace {
         ASSERT_TRUE(errMsg.empty());
 
         errMsg.clear();
-        ASSERT_FALSE(deleter.queueDelete(ns, BSON("x" << 120), BSON("x" << 140),  BSON("x" << 1),
+        ASSERT_FALSE(deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                                         ns, BSON("x" << 120), BSON("x" << 140),  BSON("x" << 1),
                                          false, NULL /* notifier not needed */, &errMsg));
         ASSERT_FALSE(errMsg.empty());
 
         errMsg.clear();
-        ASSERT_FALSE(deleter.deleteNow(ns, BSON("x" << 120), BSON("x" << 140),
+        ASSERT_FALSE(deleter.deleteNow(noTxn, ns, BSON("x" << 120), BSON("x" << 140),
                                        BSON("x" << 1), false, &errMsg));
         ASSERT_FALSE(errMsg.empty());
 
@@ -400,7 +412,8 @@ namespace {
         env->addCursorId(ns, 58);
 
         Notification notifyDone;
-        deleter.queueDelete(ns, BSON("x" << 0), BSON("x" << 10), BSON("x" << 1),
+        deleter.queueDelete(TransactionExperiment::factoryNULL, // XXX SERVER-13931
+                            ns, BSON("x" << 0), BSON("x" << 10), BSON("x" << 1),
                             false, &notifyDone, NULL /* errMsg not needed */);
 
         string errMsg;
@@ -430,6 +443,7 @@ namespace {
         string delErrMsg;
         boost::thread deleterThread = boost::thread(boost::bind(&RangeDeleter::deleteNow,
                                                                 &deleter,
+                                                                noTxn,
                                                                 ns,
                                                                 BSON("x" << 64),
                                                                 BSON("x" << 70),
@@ -468,7 +482,7 @@ namespace {
         ASSERT_FALSE(deleter.removeFromBlackList(ns, BSON("x" << 1234), BSON("x" << 9000)));
 
         // Range should still be blacklisted
-        ASSERT_FALSE(deleter.deleteNow(ns, BSON("x" << 2000), BSON("x" << 4000), BSON("x" << 1),
+        ASSERT_FALSE(deleter.deleteNow(noTxn, ns, BSON("x" << 2000), BSON("x" << 4000), BSON("x" << 1),
                                        false, NULL /* errMsg not needed */));
 
         deleter.stopWorkers();
@@ -485,14 +499,14 @@ namespace {
         ASSERT_TRUE(errMsg.empty());
 
         errMsg.clear();
-        ASSERT_FALSE(deleter.deleteNow(ns, BSON("x" << 600), BSON("x" << 700),
+        ASSERT_FALSE(deleter.deleteNow(noTxn, ns, BSON("x" << 600), BSON("x" << 700),
                                        BSON("x" << 1), false, &errMsg));
         ASSERT_FALSE(errMsg.empty());
 
         ASSERT_TRUE(deleter.removeFromBlackList(ns, BSON("x" << 500), BSON("x" << 801)));
 
         errMsg.clear();
-        ASSERT_TRUE(deleter.deleteNow(ns, BSON("x" << 600), BSON("x" << 700),
+        ASSERT_TRUE(deleter.deleteNow(noTxn, ns, BSON("x" << 600), BSON("x" << 700),
                                       BSON("x" << 1), false, &errMsg));
         ASSERT_TRUE(errMsg.empty());
 
@@ -507,7 +521,7 @@ namespace {
         deleter.addToBlackList("foo.bar", BSON("x" << 100), BSON("x" << 200),
                                NULL /* errMsg not needed */);
 
-        ASSERT_TRUE(deleter.deleteNow("test.user", BSON("x" << 120), BSON("x" << 140),
+        ASSERT_TRUE(deleter.deleteNow(noTxn, "test.user", BSON("x" << 120), BSON("x" << 140),
                                       BSON("x" << 1), true, NULL /* errMsg not needed */));
 
         deleter.stopWorkers();
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index 0be9d7a9bd6..61cb23f914b 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -705,7 +705,7 @@ namespace mongo {
             while (!done) {
                 BufBuilder bb;
                 BSONObjBuilder ob;
-                _runCommands(ns, o, bb, ob, true, 0);
+                _runCommands(txn, ns, o, bb, ob, true, 0);
                 // _runCommands takes care of adjusting opcounters for command counting.
                 Status status = Command::getStatusFromCommandResult(ob.done());
                 switch (status.code()) {
diff --git a/src/mongo/db/repl/replset_web_handler.cpp b/src/mongo/db/repl/replset_web_handler.cpp
index 27ce6a61853..5cd7b14ae48 100644
--- a/src/mongo/db/repl/replset_web_handler.cpp
+++ b/src/mongo/db/repl/replset_web_handler.cpp
@@ -53,7 +53,8 @@ namespace {
             return startsWith( url , "/_replSet" );
         }
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
 
diff --git a/src/mongo/db/repl/resync.cpp b/src/mongo/db/repl/resync.cpp
index 1adc44903e6..1c4322d81cd 100644
--- a/src/mongo/db/repl/resync.cpp
+++ b/src/mongo/db/repl/resync.cpp
@@ -57,7 +57,8 @@ namespace mongo {
         }
 
         CmdResync() : Command("resync") { }
-        virtual bool run(const string& dbname,
+        virtual bool newRun(TransactionExperiment* txn,
+                         const string& dbname,
                          BSONObj& cmdObj,
                          int,
                          string& errmsg,
@@ -67,7 +68,6 @@ namespace mongo {
             const std::string ns = parseNs(dbname, cmdObj);
             Lock::GlobalWrite globalWriteLock;
             Client::Context ctx(ns);
-            DurTransaction txn;
 
             if (replSettings.usingReplSets()) {
                 if (theReplSet->isPrimary()) {
@@ -90,7 +90,7 @@ namespace mongo {
             if ( !waitForSyncToFinish( errmsg ) )
                 return false;
 
-            ReplSource::forceResyncDead( &txn, "client" );
+            ReplSource::forceResyncDead( txn, "client" );
             result.append( "info", "triggered resync for all sources" );
             return true;
         }
diff --git a/src/mongo/db/restapi.cpp b/src/mongo/db/restapi.cpp
index bb06d522491..bb2243272ea 100644
--- a/src/mongo/db/restapi.cpp
+++ b/src/mongo/db/restapi.cpp
@@ -66,7 +66,8 @@ namespace mongo {
                 url.find_last_of( '/' ) > 0;
         }
 
-        virtual void handle( const char *rq, const std::string& url, BSONObj params,
+        virtual void handle( TransactionExperiment* txn,
+                             const char *rq, const std::string& url, BSONObj params,
                              string& responseMsg, int& responseCode,
                              vector<string>& headers,  const SockAddr &from ) {
 
diff --git a/src/mongo/db/storage/mmap_v1/dur_transaction.cpp b/src/mongo/db/storage/mmap_v1/dur_transaction.cpp
index b4b904527c9..147dc9a71e2 100644
--- a/src/mongo/db/storage/mmap_v1/dur_transaction.cpp
+++ b/src/mongo/db/storage/mmap_v1/dur_transaction.cpp
@@ -74,4 +74,8 @@ namespace mongo {
         return Status( ErrorCodes::Interrupted, killed );
     }
 
+    TransactionExperiment* DurTransaction::factory() {
+        return new DurTransaction();
+    }
+
 }  // namespace mongo
diff --git a/src/mongo/db/storage/mmap_v1/dur_transaction.h b/src/mongo/db/storage/mmap_v1/dur_transaction.h
index c6fe30e98b4..b4a2bd009e3 100644
--- a/src/mongo/db/storage/mmap_v1/dur_transaction.h
+++ b/src/mongo/db/storage/mmap_v1/dur_transaction.h
@@ -62,6 +62,11 @@ namespace mongo {
 
         virtual Status checkForInterruptNoAssert() const;
 
+        /**
+         * Returns a DurTransaction. Caller takes ownership.
+         */
+        static TransactionExperiment* factory();
+
     };
 
 }  // namespace mongo
diff --git a/src/mongo/db/storage/transaction.h b/src/mongo/db/storage/transaction.h
index a025b8f283f..2684342e542 100644
--- a/src/mongo/db/storage/transaction.h
+++ b/src/mongo/db/storage/transaction.h
@@ -125,6 +125,23 @@ namespace mongo {
             return x;
         }
 
+        /**
+         * Returns a TransactionExperiment. Caller takes ownership.
+         *
+         * This interface is used for functions that need to create transactions (aka OpCtx), but
+         * don't know which implementation they should create. It allows the calling code to make
+         * that decision for them.
+         *
+         * TODO come up with a better Factory API once we split this class up (SERVER-13931).
+         */
+        typedef TransactionExperiment* (*Factory)();
+
+        /**
+         * A TransactionExperiment::Factory that always returns NULL. For things that shouldn't be
+         * touching their txns such as mongos or some unittests.
+         */
+        static TransactionExperiment* factoryNULL() { return NULL; }
+
     protected:
         TransactionExperiment() {}
     };