SERVER-36498 Gate "state" field in config.transactions on FCV and remove entries with state on downgrade

2 files changed, 24 insertions, 14 deletions

diff --git a/src/mongo/db/repl/session_update_tracker.cpp b/src/mongo/db/repl/session_update_tracker.cpp
index 32cc3466879..958e77f1497 100644
--- a/src/mongo/db/repl/session_update_tracker.cpp
+++ b/src/mongo/db/repl/session_update_tracker.cpp
@@ -35,6 +35,7 @@
 
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/repl/oplog_entry.h"
+#include "mongo/db/server_options.h"
 #include "mongo/db/session.h"
 #include "mongo/db/session_txn_record_gen.h"
 #include "mongo/util/assert_util.h"
@@ -68,20 +69,25 @@ boost::optional<repl::OplogEntry> createMatchingTransactionTableUpdate(
         newTxnRecord.setLastWriteOpTime(entry.getOpTime());
         newTxnRecord.setLastWriteDate(*entry.getWallClockTime());
 
-        switch (entry.getCommandType()) {
-            case repl::OplogEntry::CommandType::kApplyOps:
-                newTxnRecord.setState(entry.shouldPrepare() ? DurableTxnStateEnum::kPrepared
-                                                            : DurableTxnStateEnum::kCommitted);
-                break;
-            case repl::OplogEntry::CommandType::kCommitTransaction:
-                newTxnRecord.setState(DurableTxnStateEnum::kCommitted);
-                break;
-            case repl::OplogEntry::CommandType::kAbortTransaction:
-                newTxnRecord.setState(DurableTxnStateEnum::kAborted);
-                break;
-            default:
-                break;
+        // "state" is a new field in 4.2.
+        if (serverGlobalParams.featureCompatibility.getVersion() >=
+            ServerGlobalParams::FeatureCompatibility::Version::kUpgradingTo42) {
+            switch (entry.getCommandType()) {
+                case repl::OplogEntry::CommandType::kApplyOps:
+                    newTxnRecord.setState(entry.shouldPrepare() ? DurableTxnStateEnum::kPrepared
+                                                                : DurableTxnStateEnum::kCommitted);
+                    break;
+                case repl::OplogEntry::CommandType::kCommitTransaction:
+                    newTxnRecord.setState(DurableTxnStateEnum::kCommitted);
+                    break;
+                case repl::OplogEntry::CommandType::kAbortTransaction:
+                    newTxnRecord.setState(DurableTxnStateEnum::kAborted);
+                    break;
+                default:
+                    break;
+            }
         }
+
         return newTxnRecord.toBSON();
     }();
 
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index c811ff0dd82..6ac27643f1e 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -907,12 +907,16 @@ bool SyncTail::tryPopAndWaitForMore(OperationContext* opCtx,
     // Commands must be processed one at a time. The only exception to this is applyOps because
     // applyOps oplog entries are effectively containers for CRUD operations. Therefore, it is safe
     // to batch applyOps commands with CRUD operations when reading from the oplog buffer.
+    //
     // Oplog entries on 'system.views' should also be processed one at a time. View catalog
     // immediately reflects changes for each oplog entry so we can see inconsistent view catalog if
     // multiple oplog entries on 'system.views' are being applied out of the original order.
+    //
+    // Process updates to 'admin.system.version' individually as well so the secondary's FCV when
+    // processing each operation matches the primary's when committing that operation.
     if ((entry.isCommand() &&
          (entry.getCommandType() != OplogEntry::CommandType::kApplyOps || entry.shouldPrepare())) ||
-        entry.getNss().isSystemDotViews()) {
+        entry.getNss().isSystemDotViews() || entry.getNss().isServerConfigurationCollection()) {
         if (ops->getCount() == 1) {
             // apply commands one-at-a-time
             _consume(opCtx, oplogBuffer);