SERVER-35695 Add server parameter to enable transactions on inMemory

storage engine

1 files changed, 16 insertions, 1 deletions

diff --git a/src/mongo/db/initialize_operation_session_info.cpp b/src/mongo/db/initialize_operation_session_info.cpp
index 965dc0f1e53..446170d63f2 100644
--- a/src/mongo/db/initialize_operation_session_info.cpp
+++ b/src/mongo/db/initialize_operation_session_info.cpp
@@ -34,9 +34,16 @@
 #include "mongo/db/logical_session_cache.h"
 #include "mongo/db/logical_session_id_helpers.h"
 #include "mongo/db/operation_context.h"
+#include "mongo/db/server_parameters.h"
 
 namespace mongo {
 
+// Allows multi-document transactions to run with the 'inMemory' storage engine. This flag should
+// ONLY be used for testing purposes. Production systems should not run transactions on the
+// 'inMemory' storage engines until "rollback to a timestamp" is supported on the 'inMemory' storage
+// engine (see SERVER-34165).
+MONGO_EXPORT_SERVER_PARAMETER(enableInMemoryTransactions, bool, false);
+
 boost::optional<OperationSessionInfoFromClient> initializeOperationSessionInfo(
     OperationContext* opCtx,
     const BSONObj& requestBody,
@@ -107,10 +114,18 @@ boost::optional<OperationSessionInfoFromClient> initializeOperationSessionInfo(
         uassert(ErrorCodes::InvalidOptions,
                 "Specifying autocommit=true is not allowed.",
                 !osi.getAutocommit().value());
+
+        // We allow transactions to run on in-memory storage engines for testing purposes.
+        bool allowInMemoryTransactions = false;
+        auto storageEngine = opCtx->getServiceContext()->getStorageEngine();
+        if (storageEngine) {
+            allowInMemoryTransactions =
+                storageEngine->isEphemeral() && enableInMemoryTransactions.load();
+        }
         uassert(ErrorCodes::IllegalOperation,
                 "Multi-document transactions are only allowed on storage engines that support "
                 "recover to stable timestamp.",
-                supportsRecoverToStableTimestamp);
+                supportsRecoverToStableTimestamp || allowInMemoryTransactions);
     } else {
         uassert(ErrorCodes::InvalidOptions,
                 "'startTransaction' field requires 'autocommit' field to also be specified",