SERVER-9861 explicitly forget temporary collections for versioning in M/R

4 files changed, 69 insertions, 1 deletions

diff --git a/jstests/sharding/forget_mr_temp_ns.js b/jstests/sharding/forget_mr_temp_ns.js
new file mode 100644
index 00000000000..54eeb88d9b5
--- /dev/null
+++ b/jstests/sharding/forget_mr_temp_ns.js
@@ -0,0 +1,46 @@
+//
+// Tests whether we forget M/R's temporary namespaces for sharded output
+//
+
+var options = { separateConfig : true };
+
+var st = new ShardingTest({ shards : 1, mongos : 1, other : options });
+
+var mongos = st.s0;
+var admin = mongos.getDB( "admin" );
+var coll = mongos.getCollection( "foo.bar" );
+var outputColl = mongos.getCollection( (coll.getDB() + "") + ".mrOutput" ); 
+
+for ( var i = 0; i < 10; i++ ) {
+    coll.insert({ _id : i, even : (i % 2 == 0) });
+}
+assert.eq( null, coll.getDB().getLastError() );
+
+var map = function() { emit( this.even, 1 ); };
+var reduce = function( key, values ) { return Array.sum(values); };
+
+out = coll.mapReduce( map, reduce, { out: { reduce : outputColl.getName(), sharded: true } } );
+
+printjson( out );
+printjson( outputColl.find().toArray() );
+
+var mongodThreadStats = st.shard0.getDB( "admin" ).runCommand({ shardConnPoolStats : 1 }).threads;
+var mongosThreadStats = admin.runCommand({ shardConnPoolStats : 1 }).threads;
+
+printjson( mongodThreadStats );
+printjson( mongosThreadStats );
+
+var checkForSeenNS = function( threadStats, regex ) {
+    for ( var i = 0; i < threadStats.length; i++ ) {
+        var seenNSes = threadStats[i].seenNS;
+        for ( var j = 0; j < seenNSes.length; j++ ) {
+            assert( !( regex.test( seenNSes ) ) );
+        }
+    }
+}
+
+checkForSeenNS( mongodThreadStats, /^foo.tmp/ );
+checkForSeenNS( mongosThreadStats, /^foo.tmp/ );
+
+st.stop();
+
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 84fbfa8cb4d..1b237d3ed7f 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -301,8 +301,13 @@ namespace mongo {
          */
         void State::dropTempCollections() {
             _db.dropCollection(_config.tempNamespace);
-            if (_useIncremental)
+            // Always forget about temporary namespaces, so we don't cache lots of them
+            ShardConnection::forgetNS( _config.tempNamespace );
+            if (_useIncremental) {
                 _db.dropCollection(_config.incLong);
+                ShardConnection::forgetNS( _config.incLong );
+            }
+
         }
 
         /**
@@ -1475,6 +1480,9 @@ namespace mongo {
                         break;
                 }
 
+                // Forget temporary input collection, if output is sharded collection
+                ShardConnection::forgetNS( inputNS );
+
                 result.append( "chunkSizes" , chunkSizes.arr() );
 
                 long long outputCount = state.postProcessCollection(op, pm);
diff --git a/src/mongo/s/shard.h b/src/mongo/s/shard.h
index e917baa0986..39504311a65 100644
--- a/src/mongo/s/shard.h
+++ b/src/mongo/s/shard.h
@@ -307,6 +307,11 @@ namespace mongo {
          */
         static void clearPool();
 
+        /**
+         * Forgets a namespace to prevent future versioning.
+         */
+        static void forgetNS( const string& ns );
+
     private:
         void _init();
         void _finishInit();
diff --git a/src/mongo/s/shardconnection.cpp b/src/mongo/s/shardconnection.cpp
index 61b47904147..6d21234071a 100644
--- a/src/mongo/s/shardconnection.cpp
+++ b/src/mongo/s/shardconnection.cpp
@@ -322,6 +322,11 @@ namespace mongo {
             _hosts.clear();
         }
 
+        void forgetNS( const string& ns ) {
+            scoped_spinlock lock( _lock );
+            _seenNS.erase( ns );
+        }
+
         // -----
 
         static thread_specific_ptr<ClientConnections> _perThread;
@@ -487,4 +492,8 @@ namespace mongo {
         shardConnectionPool.clear();
         ClientConnections::threadInstance()->clearPool();
     }
+
+    void ShardConnection::forgetNS( const string& ns ) {
+        ClientConnections::threadInstance()->forgetNS( ns );
+    }
 }