SERVER-21604 v3.0 mongos fails to ping config.mongos if config servers are v3.2

5 files changed, 25 insertions, 9 deletions

diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index ea45097bacf..7ed7b43985f 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -344,7 +344,7 @@ public:
         const FindAndModifyRequest& args = parseStatus.getValue();
         const NamespaceString& nsString = args.getNamespaceString();
 
-        StatusWith<WriteConcernOptions> wcResult = extractWriteConcern(cmdObj, dbName);
+        StatusWith<WriteConcernOptions> wcResult = extractWriteConcern(txn, cmdObj, dbName);
         if (!wcResult.isOK()) {
             return appendCommandStatus(result, wcResult.getStatus());
         }
diff --git a/src/mongo/db/commands/get_last_error.cpp b/src/mongo/db/commands/get_last_error.cpp
index b50059dfafe..dfb8a6d7097 100644
--- a/src/mongo/db/commands/get_last_error.cpp
+++ b/src/mongo/db/commands/get_last_error.cpp
@@ -224,7 +224,7 @@ public:
 
         if (status.isOK()) {
             // Ensure options are valid for this host
-            status = validateWriteConcern(writeConcern, dbname);
+            status = validateWriteConcern(txn, writeConcern, dbname);
         }
 
         if (!status.isOK()) {
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index f53bc5097eb..4d5f625c948 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -131,7 +131,7 @@ bool WriteCmd::run(OperationContext* txn,
         return appendCommandStatus(result, Status(ErrorCodes::FailedToParse, errMsg));
     }
 
-    StatusWith<WriteConcernOptions> wcStatus = extractWriteConcern(cmdObj, dbName);
+    StatusWith<WriteConcernOptions> wcStatus = extractWriteConcern(txn, cmdObj, dbName);
 
     if (!wcStatus.isOK()) {
         return appendCommandStatus(result, wcStatus.getStatus());
diff --git a/src/mongo/db/write_concern.cpp b/src/mongo/db/write_concern.cpp
index e5e700fa49e..6f447d8b666 100644
--- a/src/mongo/db/write_concern.cpp
+++ b/src/mongo/db/write_concern.cpp
@@ -42,6 +42,7 @@
 #include "mongo/db/stats/timer_stats.h"
 #include "mongo/db/storage/storage_engine.h"
 #include "mongo/db/write_concern_options.h"
+#include "mongo/rpc/protocol.h"
 
 namespace mongo {
 
@@ -78,7 +79,8 @@ void addJournalSyncForWMajority(WriteConcernOptions* writeConcern) {
 const std::string kLocalDB = "local";
 }  // namespace
 
-StatusWith<WriteConcernOptions> extractWriteConcern(const BSONObj& cmdObj,
+StatusWith<WriteConcernOptions> extractWriteConcern(OperationContext* txn,
+                                                    const BSONObj& cmdObj,
                                                     const std::string& dbName) {
     // The default write concern if empty is w : 1
     // Specifying w : 0 is/was allowed, but is interpreted identically to w : 1
@@ -111,7 +113,7 @@ StatusWith<WriteConcernOptions> extractWriteConcern(const BSONObj& cmdObj,
         return wcStatus;
     }
 
-    wcStatus = validateWriteConcern(writeConcern, dbName);
+    wcStatus = validateWriteConcern(txn, writeConcern, dbName);
     if (!wcStatus.isOK()) {
         return wcStatus;
     }
@@ -121,7 +123,9 @@ StatusWith<WriteConcernOptions> extractWriteConcern(const BSONObj& cmdObj,
 
     return writeConcern;
 }
-Status validateWriteConcern(const WriteConcernOptions& writeConcern, const std::string& dbName) {
+Status validateWriteConcern(OperationContext* txn,
+                            const WriteConcernOptions& writeConcern,
+                            const std::string& dbName) {
     const bool isJournalEnabled = getGlobalServiceContext()->getGlobalStorageEngine()->isDurable();
 
     if (writeConcern.syncMode == WriteConcernOptions::JOURNAL && !isJournalEnabled) {
@@ -135,6 +139,15 @@ Status validateWriteConcern(const WriteConcernOptions& writeConcern, const std::
         repl::getGlobalReplicationCoordinator()->getReplicationMode();
 
     if (isConfigServer) {
+        auto protocol = rpc::getOperationProtocol(txn);
+        // This here only for v3.0 backwards compatibility.
+        if (serverGlobalParams.configsvrMode != CatalogManager::ConfigServerMode::CSRS &&
+            replMode != repl::ReplicationCoordinator::modeReplSet &&
+            protocol == rpc::Protocol::kOpQuery && writeConcern.wNumNodes == 0 &&
+            writeConcern.wMode.empty()) {
+            return Status::OK();
+        }
+
         if (!writeConcern.validForConfigServers()) {
             return Status(
                 ErrorCodes::BadValue,
@@ -224,7 +237,7 @@ Status waitForWriteConcern(OperationContext* txn,
                            WriteConcernResult* result) {
     // We assume all options have been validated earlier, if not, programming error.
     // Passing localDB name is a hack to avoid more rigorous check that performed for non local DB.
-    dassert(validateWriteConcern(writeConcern, kLocalDB).isOK());
+    dassert(validateWriteConcern(txn, writeConcern, kLocalDB).isOK());
 
     // We should never be waiting for write concern while holding any sort of lock, because this may
     // lead to situations where the replication heartbeats are stalled.
diff --git a/src/mongo/db/write_concern.h b/src/mongo/db/write_concern.h
index 146a7ec94d0..873e6114af1 100644
--- a/src/mongo/db/write_concern.h
+++ b/src/mongo/db/write_concern.h
@@ -54,13 +54,16 @@ void setupSynchronousCommit(OperationContext* txn);
  * Verifies that the writeConcern is of type Object (BSON type) and
  * that the resulting writeConcern is valid for this particular host.
  */
-StatusWith<WriteConcernOptions> extractWriteConcern(const BSONObj& cmdObj,
+StatusWith<WriteConcernOptions> extractWriteConcern(OperationContext* txn,
+                                                    const BSONObj& cmdObj,
                                                     const std::string& dbName);
 
 /**
  * Verifies that a WriteConcern is valid for this particular host.
  */
-Status validateWriteConcern(const WriteConcernOptions& writeConcern, const std::string& dbName);
+Status validateWriteConcern(OperationContext* txn,
+                            const WriteConcernOptions& writeConcern,
+                            const std::string& dbName);
 
 struct WriteConcernResult {
     WriteConcernResult() {