SERVER-22540 Commands that do writes on mongos should take a writeConcern and aggregate results

19 files changed, 301 insertions, 29 deletions

diff --git a/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp b/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
index 3fdc0b7bcb3..1d1e5fa40c1 100644
--- a/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
+++ b/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
@@ -72,7 +72,6 @@ public:
         return true;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         // This is required to be true to support moveChunk.
         return true;
@@ -200,7 +199,6 @@ public:
         return true;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
index 9f6216b607d..64ff516acbd 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
@@ -499,10 +499,11 @@ Status CatalogManagerReplicaSet::dropCollection(OperationContext* txn, const Nam
             shardEntry.getName(),
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             ns.db().toString(),
-            BSON("drop" << ns.coll()));
+            BSON("drop" << ns.coll() << "writeConcern" << txn->getWriteConcern().toBSON()));
 
         if (!dropResult.isOK()) {
-            return dropResult.getStatus();
+            return Status(dropResult.getStatus().code(),
+                          dropResult.getStatus().reason() + " at " + shardEntry.getName());
         }
 
         auto dropStatus = getStatusFromCommandResult(dropResult.getValue());
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
index ab49bad9a13..abdb370f180 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
@@ -92,7 +92,9 @@ public:
         onCommand([this, shard](const RemoteCommandRequest& request) {
             ASSERT_EQ(HostAndPort(shard.getHost()), request.target);
             ASSERT_EQ(_dropNS.db(), request.dbname);
-            ASSERT_EQ(BSON("drop" << _dropNS.coll()), request.cmdObj);
+            ASSERT_EQ(BSON("drop" << _dropNS.coll() << "writeConcern"
+                                  << BSON("w" << 0 << "wtimeout" << 0)),
+                      request.cmdObj);
 
             ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
 
@@ -213,7 +215,9 @@ TEST_F(DropColl2ShardTest, NSNotFound) {
     onCommand([this](const RemoteCommandRequest& request) {
         ASSERT_EQ(HostAndPort(shard1().getHost()), request.target);
         ASSERT_EQ(dropNS().db(), request.dbname);
-        ASSERT_EQ(BSON("drop" << dropNS().coll()), request.cmdObj);
+        ASSERT_EQ(
+            BSON("drop" << dropNS().coll() << "writeConcern" << BSON("w" << 0 << "wtimeout" << 0)),
+            request.cmdObj);
 
         ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
 
@@ -223,7 +227,9 @@ TEST_F(DropColl2ShardTest, NSNotFound) {
     onCommand([this](const RemoteCommandRequest& request) {
         ASSERT_EQ(HostAndPort(shard2().getHost()), request.target);
         ASSERT_EQ(dropNS().db(), request.dbname);
-        ASSERT_EQ(BSON("drop" << dropNS().coll()), request.cmdObj);
+        ASSERT_EQ(
+            BSON("drop" << dropNS().coll() << "writeConcern" << BSON("w" << 0 << "wtimeout" << 0)),
+            request.cmdObj);
 
         ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
 
diff --git a/src/mongo/s/client/shard_registry.cpp b/src/mongo/s/client/shard_registry.cpp
index 3d7f20cc095..e83b687473a 100644
--- a/src/mongo/s/client/shard_registry.cpp
+++ b/src/mongo/s/client/shard_registry.cpp
@@ -163,6 +163,12 @@ const ShardRegistry::ErrorCodesSet ShardRegistry::kAllRetriableErrors{
     ErrorCodes::NetworkTimeout,
     ErrorCodes::InterruptedDueToReplStateChange};
 
+const ShardRegistry::ErrorCodesSet ShardRegistry::kWriteConcernErrors{
+    ErrorCodes::WriteConcernFailed,
+    ErrorCodes::WriteConcernLegacyOK,
+    ErrorCodes::UnknownReplWriteConcern,
+    ErrorCodes::CannotSatisfyWriteConcern};
+
 ShardRegistry::ShardRegistry(std::unique_ptr<RemoteCommandTargeterFactory> targeterFactory,
                              std::unique_ptr<executor::TaskExecutorPool> executorPool,
                              executor::NetworkInterface* network,
diff --git a/src/mongo/s/client/shard_registry.h b/src/mongo/s/client/shard_registry.h
index a025ceef331..be09dc636ff 100644
--- a/src/mongo/s/client/shard_registry.h
+++ b/src/mongo/s/client/shard_registry.h
@@ -316,6 +316,11 @@ public:
      */
     static const ErrorCodesSet kAllRetriableErrors;
 
+    /**
+     * Set of error codes that specify write concern related errors.
+     */
+    static const ErrorCodesSet kWriteConcernErrors;
+
 private:
     using ShardMap = std::unordered_map<ShardId, std::shared_ptr<Shard>>;
 
diff --git a/src/mongo/s/commands/SConscript b/src/mongo/s/commands/SConscript
index 676c4840fa6..3ea20a66f1c 100644
--- a/src/mongo/s/commands/SConscript
+++ b/src/mongo/s/commands/SConscript
@@ -62,6 +62,7 @@ env.Library(
         'cluster_write_cmd.cpp',
         'commands_public.cpp',
         'run_on_all_shards_cmd.cpp',
+        'sharded_command_processing.cpp',
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/client/parallel',
diff --git a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
index e6accb504c6..2400d23931a 100644
--- a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
+++ b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
@@ -38,6 +38,7 @@
 #include "mongo/s/client/shard_connection.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/catalog/catalog_cache.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/config.h"
 #include "mongo/s/chunk_manager.h"
 #include "mongo/s/cluster_explain.h"
@@ -45,6 +46,7 @@
 #include "mongo/s/grid.h"
 #include "mongo/s/stale_exception.h"
 #include "mongo/s/strategy.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 #include "mongo/util/timer.h"
 
 namespace mongo {
@@ -228,7 +230,13 @@ private:
             throw RecvStaleConfigException("FindAndModify", res);
         }
 
-        result.appendElements(res);
+        // First append the properly constructed writeConcernError. It will then be skipped
+        // in appendElementsUnique.
+        if (auto wcErrorElem = res["writeConcernError"]) {
+            appendWriteConcernErrorToCmdResponse(shardId, wcErrorElem, result);
+        }
+
+        result.appendElementsUnique(res);
         return ok;
     }
 
diff --git a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
index 662f7278367..d016e7713a4 100644
--- a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
@@ -45,12 +45,14 @@
 #include "mongo/s/chunk.h"
 #include "mongo/s/chunk_manager.h"
 #include "mongo/s/commands/cluster_commands_common.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/config.h"
 #include "mongo/s/catalog/dist_lock_manager.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/db_util.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/strategy.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 #include "mongo/stdx/chrono.h"
 #include "mongo/util/log.h"
 
@@ -95,7 +97,7 @@ BSONObj fixForShards(const BSONObj& orig,
             fn == "sort" || fn == "scope" || fn == "verbose" || fn == "$queryOptions" ||
             fn == "readConcern" || fn == LiteParsedQuery::cmdOptionMaxTimeMS) {
             b.append(e);
-        } else if (fn == "out" || fn == "finalize") {
+        } else if (fn == "out" || fn == "finalize" || fn == "writeConcern") {
             // We don't want to copy these
         } else {
             badShardedField = fn;
@@ -282,7 +284,11 @@ public:
             bool ok = conn->runCommand(dbname, cmdObj, res);
             conn.done();
 
-            result.appendElements(res);
+            if (auto wcErrorElem = res["writeConcernError"]) {
+                appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, result);
+            }
+
+            result.appendElementsUnique(res);
             return ok;
         }
 
@@ -382,6 +388,7 @@ public:
         finalCmd.append("inputDB", dbname);
         finalCmd.append("shardedOutputCollection", shardResultCollection);
         finalCmd.append("shards", shardResultsB.done());
+        finalCmd.append("writeConcern", txn->getWriteConcern().toBSON());
 
         BSONObj shardCounts = shardCountsB.done();
         finalCmd.append("shardCounts", shardCounts);
@@ -410,6 +417,7 @@ public:
 
         bool ok = true;
         BSONObj singleResult;
+        bool hasWCError = false;
 
         if (!shardedOutput) {
             const auto shard = grid.shardRegistry()->getShard(txn, confOut->getPrimaryId());
@@ -425,6 +433,12 @@ public:
             outputCount = counts.getIntField("output");
 
             conn.done();
+            if (!hasWCError) {
+                if (auto wcErrorElem = singleResult["writeConcernError"]) {
+                    appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, result);
+                    hasWCError = true;
+                }
+            }
         } else {
             LOG(1) << "MR with sharded output, NS=" << outputCollNss.ns();
 
@@ -501,6 +515,13 @@ public:
                         server = shard->getConnString().toString();
                     }
                     singleResult = mrResult.result;
+                    if (!hasWCError) {
+                        if (auto wcErrorElem = singleResult["writeConcernError"]) {
+                            appendWriteConcernErrorToCmdResponse(
+                                mrResult.shardTargetId, wcErrorElem, result);
+                            hasWCError = true;
+                        }
+                    }
 
                     ok = singleResult["ok"].trueValue();
                     if (!ok) {
diff --git a/src/mongo/s/commands/cluster_move_primary_cmd.cpp b/src/mongo/s/commands/cluster_move_primary_cmd.cpp
index a09ddf30dd2..1de2564a2e1 100644
--- a/src/mongo/s/commands/cluster_move_primary_cmd.cpp
+++ b/src/mongo/s/commands/cluster_move_primary_cmd.cpp
@@ -46,9 +46,11 @@
 #include "mongo/s/catalog/catalog_cache.h"
 #include "mongo/s/catalog/catalog_manager.h"
 #include "mongo/s/client/shard_registry.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/config.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/set_shard_version_request.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
@@ -188,12 +190,13 @@ public:
         // TODO ERH - we need a clone command which replays operations from clone start to now
         //            can just use local.oplog.$main
         BSONObj cloneRes;
-        bool worked = toconn->runCommand(dbname.c_str(),
-                                         BSON("clone" << fromShard->getConnString().toString()
-                                                      << "collsToIgnore" << barr.arr()
-                                                      << bypassDocumentValidationCommandOption()
-                                                      << true << "_checkForCatalogChange" << true),
-                                         cloneRes);
+        bool worked = toconn->runCommand(
+            dbname.c_str(),
+            BSON("clone" << fromShard->getConnString().toString() << "collsToIgnore" << barr.arr()
+                         << bypassDocumentValidationCommandOption() << true
+                         << "_checkForCatalogChange" << true << "writeConcern"
+                         << txn->getWriteConcern().toBSON()),
+            cloneRes);
         toconn.done();
 
         if (!worked) {
@@ -201,6 +204,11 @@ public:
             errmsg = "clone failed";
             return false;
         }
+        bool hasWCError = false;
+        if (auto wcErrorElem = cloneRes["writeConcernError"]) {
+            appendWriteConcernErrorToCmdResponse(toShard->getId(), wcErrorElem, result);
+            hasWCError = true;
+        }
 
         const string oldPrimary = fromShard->getConnString().toString();
 
@@ -215,7 +223,15 @@ public:
                   << ", no sharded collections in " << dbname;
 
             try {
-                fromconn->dropDatabase(dbname.c_str());
+                BSONObj dropDBInfo;
+                fromconn->dropDatabase(dbname.c_str(), txn->getWriteConcern(), &dropDBInfo);
+                if (!hasWCError) {
+                    if (auto wcErrorElem = dropDBInfo["writeConcernError"]) {
+                        appendWriteConcernErrorToCmdResponse(
+                            fromShard->getId(), wcErrorElem, result);
+                        hasWCError = true;
+                    }
+                }
             } catch (DBException& e) {
                 e.addContext(str::stream() << "movePrimary could not drop the database " << dbname
                                            << " on " << oldPrimary);
@@ -239,7 +255,17 @@ public:
                     try {
                         log() << "movePrimary dropping cloned collection " << el.String() << " on "
                               << oldPrimary;
-                        fromconn->dropCollection(el.String());
+                        BSONObj dropCollInfo;
+                        fromconn->dropCollection(
+                            el.String(), txn->getWriteConcern(), &dropCollInfo);
+                        if (!hasWCError) {
+                            if (auto wcErrorElem = dropCollInfo["writeConcernError"]) {
+                                appendWriteConcernErrorToCmdResponse(
+                                    fromShard->getId(), wcErrorElem, result);
+                                hasWCError = true;
+                            }
+                        }
+
                     } catch (DBException& e) {
                         e.addContext(str::stream()
                                      << "movePrimary could not drop the cloned collection "
diff --git a/src/mongo/s/commands/cluster_pipeline_cmd.cpp b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
index 3b558c597ca..e81f698ea53 100644
--- a/src/mongo/s/commands/cluster_pipeline_cmd.cpp
+++ b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
@@ -49,10 +49,12 @@
 #include "mongo/s/client/shard_connection.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/commands/cluster_commands_common.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/config.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/query/store_possible_cursor.h"
 #include "mongo/s/stale_exception.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
@@ -228,6 +230,8 @@ public:
                 Value(cmdObj[LiteParsedQuery::cmdOptionMaxTimeMS]);
         }
 
+        mergeCmd.setField("writeConcern", Value(cmdObj["writeConcern"]));
+
         // Not propagating readConcern to merger since it doesn't do local reads.
 
         string outputNsOrEmpty;
@@ -247,9 +251,13 @@ public:
             aggRunCommand(conn.get(), dbname, mergeCmd.freeze().toBson(), options);
         conn.done();
 
+        if (auto wcErrorElem = mergedResults["writeConcernError"]) {
+            appendWriteConcernErrorToCmdResponse(mergingShardId, wcErrorElem, result);
+        }
+
         // Copy output from merging (primary) shard to the output object from our command.
         // Also, propagates errmsg and code if ok == false.
-        result.appendElements(mergedResults);
+        result.appendElementsUnique(mergedResults);
 
         return mergedResults["ok"].trueValue();
     }
@@ -421,7 +429,14 @@ bool PipelineCommand::aggPassthrough(OperationContext* txn,
     ShardConnection conn(shard->getConnString(), "");
     BSONObj result = aggRunCommand(conn.get(), conf->name(), cmd, queryOptions);
     conn.done();
-    out.appendElements(result);
+
+    // First append the properly constructed writeConcernError. It will then be skipped
+    // in appendElementsUnique.
+    if (auto wcErrorElem = result["writeConcernError"]) {
+        appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, out);
+    }
+
+    out.appendElementsUnique(result);
     return result["ok"].trueValue();
 }
 
diff --git a/src/mongo/s/commands/cluster_user_management_commands.cpp b/src/mongo/s/commands/cluster_user_management_commands.cpp
index a96306ee6ed..ecff2fa2005 100644
--- a/src/mongo/s/commands/cluster_user_management_commands.cpp
+++ b/src/mongo/s/commands/cluster_user_management_commands.cpp
@@ -44,7 +44,9 @@
 #include "mongo/s/catalog/catalog_manager.h"
 #include "mongo/s/catalog/type_shard.h"
 #include "mongo/s/client/shard_registry.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/grid.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 
 namespace mongo {
 
@@ -833,7 +835,10 @@ namespace {
  * Upgrades each shard serially, and stops on first failure.  Returned error indicates that
  * failure.
  */
-Status runUpgradeOnAllShards(OperationContext* txn, int maxSteps, const BSONObj& writeConcern) {
+Status runUpgradeOnAllShards(OperationContext* txn,
+                             int maxSteps,
+                             const BSONObj& writeConcern,
+                             BSONObjBuilder& result) {
     BSONObjBuilder cmdObjBuilder;
     cmdObjBuilder.append("authSchemaUpgrade", 1);
     cmdObjBuilder.append("maxSteps", maxSteps);
@@ -848,6 +853,7 @@ Status runUpgradeOnAllShards(OperationContext* txn, int maxSteps, const BSONObj&
     vector<string> shardIds;
     shardRegistry->getAllShardIds(&shardIds);
 
+    bool hasWCError = false;
     for (const auto& shardId : shardIds) {
         auto cmdResult = shardRegistry->runIdempotentCommandOnShard(
             txn, shardId, ReadPreferenceSetting{ReadPreference::PrimaryOnly}, "admin", cmdObj);
@@ -857,6 +863,14 @@ Status runUpgradeOnAllShards(OperationContext* txn, int maxSteps, const BSONObj&
                           str::stream() << "Failed to run authSchemaUpgrade on shard " << shardId
                                         << causedBy(cmdResult.getStatus()));
         }
+
+        // If the result has a writeConcernError, append it.
+        if (!hasWCError) {
+            if (auto wcErrorElem = cmdResult.getValue()["writeConcernError"]) {
+                appendWriteConcernErrorToCmdResponse(shardId, wcErrorElem, result);
+                hasWCError = true;
+            }
+        }
     }
 
     return Status::OK();
@@ -910,9 +924,20 @@ public:
 
         // Optionally run the authSchemaUpgrade command on the individual shards
         if (parsedArgs.shouldUpgradeShards) {
-            status = runUpgradeOnAllShards(txn, parsedArgs.maxSteps, parsedArgs.writeConcern);
-            if (!status.isOK())
-                return appendCommandStatus(result, status);
+            status =
+                runUpgradeOnAllShards(txn, parsedArgs.maxSteps, parsedArgs.writeConcern, result);
+            if (!status.isOK()) {
+                // If the status is a write concern error, append a writeConcernError instead of
+                // and error message.
+                if (ShardRegistry::kWriteConcernErrors.count(status.code())) {
+                    WCErrorDetail wcError;
+                    wcError.setErrMessage(status.reason());
+                    wcError.setErrCode(status.code());
+                    result.append("writeConcernError", wcError.toBSON());
+                } else {
+                    return appendCommandStatus(result, status);
+                }
+            }
         }
         return true;
     }
diff --git a/src/mongo/s/commands/commands_public.cpp b/src/mongo/s/commands/commands_public.cpp
index 96293f9d698..1d533d1dd36 100644
--- a/src/mongo/s/commands/commands_public.cpp
+++ b/src/mongo/s/commands/commands_public.cpp
@@ -53,6 +53,7 @@
 #include "mongo/s/cluster_last_error_info.h"
 #include "mongo/s/commands/cluster_commands_common.h"
 #include "mongo/s/commands/run_on_all_shards_cmd.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/config.h"
 #include "mongo/s/db_util.h"
 #include "mongo/s/grid.h"
@@ -184,7 +185,12 @@ private:
         bool ok = conn->runCommand(db, cmdObj, res, passOptions() ? options : 0);
         conn.done();
 
-        result.appendElements(res);
+        // First append the properly constructed writeConcernError. It will then be skipped
+        // in appendElementsUnique.
+        if (auto wcErrorElem = res["writeConcernError"]) {
+            appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, result);
+        }
+        result.appendElementsUnique(res);
         return ok;
     }
 };
diff --git a/src/mongo/s/commands/run_on_all_shards_cmd.cpp b/src/mongo/s/commands/run_on_all_shards_cmd.cpp
index 6dd3626fde8..e9991643210 100644
--- a/src/mongo/s/commands/run_on_all_shards_cmd.cpp
+++ b/src/mongo/s/commands/run_on_all_shards_cmd.cpp
@@ -39,8 +39,10 @@
 #include "mongo/s/client/shard.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/commands/cluster_commands_common.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/db_util.h"
 #include "mongo/s/grid.h"
+#include "mongo/s/write_ops/wc_error_detail.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
@@ -103,6 +105,11 @@ bool RunOnAllShardsCommand::run(OperationContext* txn,
 
     std::list<std::shared_ptr<Future::CommandResult>>::iterator futuresit;
     std::vector<ShardId>::const_iterator shardIdsIt;
+
+    BSONElement wcErrorElem;
+    ShardId wcErrorShardId;
+    bool hasWCError = false;
+
     // We iterate over the set of shard ids and their corresponding futures in parallel.
     // TODO: replace with zip iterator if we ever decide to use one from Boost or elsewhere
     for (futuresit = futures.begin(), shardIdsIt = shardIds.cbegin();
@@ -115,11 +122,25 @@ bool RunOnAllShardsCommand::run(OperationContext* txn,
             BSONObj result = res->result();
             results.emplace_back(*shardIdsIt, result);
             subobj.append(res->getServer(), result);
+
+            if (!hasWCError) {
+                if ((wcErrorElem = result["writeConcernError"])) {
+                    wcErrorShardId = *shardIdsIt;
+                    hasWCError = true;
+                }
+            }
             continue;
         }
 
         BSONObj result = res->result();
 
+        if (!hasWCError) {
+            if ((wcErrorElem = result["writeConcernError"])) {
+                wcErrorShardId = *shardIdsIt;
+                hasWCError = true;
+            }
+        }
+
         if (result["errmsg"].type() || result["code"].numberInt() != 0) {
             result = specialErrorHandler(res->getServer(), dbName, cmdObj, result);
 
@@ -154,7 +175,12 @@ bool RunOnAllShardsCommand::run(OperationContext* txn,
 
     subobj.done();
 
+    if (hasWCError) {
+        appendWriteConcernErrorToCmdResponse(wcErrorShardId, wcErrorElem, output);
+    }
+
     BSONObj errobj = errors.done();
+
     if (!errobj.isEmpty()) {
         errmsg = errobj.toString(false, true);
 
diff --git a/src/mongo/s/commands/sharded_command_processing.cpp b/src/mongo/s/commands/sharded_command_processing.cpp
new file mode 100644
index 00000000000..04da3cc6d4e
--- /dev/null
+++ b/src/mongo/s/commands/sharded_command_processing.cpp
@@ -0,0 +1,50 @@
+/**
+ *    Copyright (C) 2013 mongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects
+ *    for all of the code used other than as permitted herein. If you modify
+ *    file(s) with this exception, you may extend this exception to your
+ *    version of the file(s), but you are not obligated to do so. If you do not
+ *    wish to do so, delete this exception statement from your version. If you
+ *    delete this exception statement from all source files in the program,
+ *    then also delete it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/s/commands/sharded_command_processing.h"
+
+#include "mongo/s/write_ops/wc_error_detail.h"
+
+namespace mongo {
+
+void appendWriteConcernErrorToCmdResponse(const std::string& shardID,
+                                          const BSONElement& wcErrorElem,
+                                          BSONObjBuilder& responseBuilder) {
+    WCErrorDetail wcError;
+    std::string errMsg;
+    auto wcErrorObj = wcErrorElem.Obj();
+    if (!wcError.parseBSON(wcErrorObj, &errMsg)) {
+        wcError.setErrMessage("Failed to parse writeConcernError: " + wcErrorObj.toString() +
+                              ", Received error: " + errMsg);
+    }
+    wcError.setErrMessage(wcError.getErrMessage() + " at " + shardID);
+    responseBuilder.append("writeConcernError", wcError.toBSON());
+}
+}  // namespace mongo
diff --git a/src/mongo/s/commands/sharded_command_processing.h b/src/mongo/s/commands/sharded_command_processing.h
new file mode 100644
index 00000000000..f0424424f89
--- /dev/null
+++ b/src/mongo/s/commands/sharded_command_processing.h
@@ -0,0 +1,43 @@
+/**
+ *    Copyright (C) 2013 mongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects
+ *    for all of the code used other than as permitted herein. If you modify
+ *    file(s) with this exception, you may extend this exception to your
+ *    version of the file(s), but you are not obligated to do so. If you do not
+ *    wish to do so, delete this exception statement from your version. If you
+ *    delete this exception statement from all source files in the program,
+ *    then also delete it in the license file.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "mongo/db/jsobj.h"
+
+namespace mongo {
+
+/**
+ * This function appends the provided writeConcernError BSONElement to the sharded response.
+ */
+void appendWriteConcernErrorToCmdResponse(const std::string& shardID,
+                                          const BSONElement& wcErrorElem,
+                                          BSONObjBuilder& responseBuilder);
+}  // namespace mongo
diff --git a/src/mongo/s/config.cpp b/src/mongo/s/config.cpp
index 58242f633b9..acb07fd1e0f 100644
--- a/src/mongo/s/config.cpp
+++ b/src/mongo/s/config.cpp
@@ -581,10 +581,17 @@ bool DBConfig::dropDatabase(OperationContext* txn, string& errmsg) {
         ScopedDbConnection conn(shard->getConnString(), 30.0);
         BSONObj res;
         if (!conn->dropDatabase(_name, txn->getWriteConcern(), &res)) {
-            errmsg = res.toString();
+            errmsg = res.toString() + " at " + _primaryId;
             return 0;
         }
         conn.done();
+        if (auto wcErrorElem = res["writeConcernError"]) {
+            auto wcError = wcErrorElem.Obj();
+            if (auto errMsgElem = wcError["errmsg"]) {
+                errmsg = errMsgElem.str() + " at " + _primaryId;
+                return false;
+            }
+        }
     }
 
     // 4
@@ -597,10 +604,17 @@ bool DBConfig::dropDatabase(OperationContext* txn, string& errmsg) {
         ScopedDbConnection conn(shard->getConnString(), 30.0);
         BSONObj res;
         if (!conn->dropDatabase(_name, txn->getWriteConcern(), &res)) {
-            errmsg = res.toString();
+            errmsg = res.toString() + " at " + shardId;
             return 0;
         }
         conn.done();
+        if (auto wcErrorElem = res["writeConcernError"]) {
+            auto wcError = wcErrorElem.Obj();
+            if (auto errMsgElem = wcError["errmsg"]) {
+                errmsg = errMsgElem.str() + " at " + shardId;
+                return false;
+            }
+        }
     }
 
     LOG(1) << "\t dropped primary db for: " << _name;
diff --git a/src/mongo/s/s_only.cpp b/src/mongo/s/s_only.cpp
index dddb4a23de2..668124a7dd4 100644
--- a/src/mongo/s/s_only.cpp
+++ b/src/mongo/s/s_only.cpp
@@ -40,6 +40,7 @@
 #include "mongo/db/commands.h"
 #include "mongo/db/service_context.h"
 #include "mongo/db/stats/counters.h"
+#include "mongo/db/write_concern_options.h"
 #include "mongo/rpc/metadata.h"
 #include "mongo/rpc/reply_builder_interface.h"
 #include "mongo/rpc/request_interface.h"
@@ -121,6 +122,27 @@ void Command::execCommandClientBasic(OperationContext* txn,
         globalOpCounters.gotCommand();
     }
 
+    StatusWith<WriteConcernOptions> wcResult =
+        WriteConcernOptions::extractWCFromCommand(cmdObj, dbname);
+    if (!wcResult.isOK()) {
+        appendCommandStatus(result, wcResult.getStatus());
+        return;
+    }
+
+    bool supportsWriteConcern = c->supportsWriteConcern(cmdObj);
+    if (!supportsWriteConcern && !wcResult.getValue().usedDefault) {
+        // This command doesn't do writes so it should not be passed a writeConcern.
+        // If we did not use the default writeConcern, one was provided when it shouldn't have
+        // been by the user.
+        appendCommandStatus(
+            result, Status(ErrorCodes::InvalidOptions, "Command does not support writeConcern"));
+        return;
+    }
+
+    if (supportsWriteConcern) {
+        txn->setWriteConcern(wcResult.getValue());
+    }
+
     std::string errmsg;
     bool ok = false;
     try {
diff --git a/src/mongo/s/write_ops/wc_error_detail.cpp b/src/mongo/s/write_ops/wc_error_detail.cpp
index 33528c42525..08abdd22064 100644
--- a/src/mongo/s/write_ops/wc_error_detail.cpp
+++ b/src/mongo/s/write_ops/wc_error_detail.cpp
@@ -176,5 +176,4 @@ const string& WCErrorDetail::getErrMessage() const {
     dassert(_isErrMessageSet);
     return _errMessage;
 }
-
 }  // namespace mongo
diff --git a/src/mongo/s/write_ops/wc_error_detail.h b/src/mongo/s/write_ops/wc_error_detail.h
index 05d07d2f090..12a8d1c2d60 100644
--- a/src/mongo/s/write_ops/wc_error_detail.h
+++ b/src/mongo/s/write_ops/wc_error_detail.h
@@ -38,7 +38,7 @@ namespace mongo {
 
 /**
  * This class represents the layout and content of the error that occurs while trying
- * to satisfy the write concern after executing the insert/update/delete runCommand.
+ * to satisfy the write concern after executing runCommand.
  */
 class WCErrorDetail {
     MONGO_DISALLOW_COPYING(WCErrorDetail);