SERVER-40009 Honor the initial sync flag when in startup without FCV document

(cherry picked from commit c0c64c95637f8f0700ac40e89dc39c30ec6f5f41)

1 files changed, 11 insertions, 2 deletions

diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index fe38d29d61d..e6dd1dc014d 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -422,11 +422,20 @@ ExitCode _initAndListen(int listenPort) {
         exitCleanly(EXIT_NEED_DOWNGRADE);
     }
 
+    auto replProcess = repl::ReplicationProcess::get(serviceContext);
+    invariant(replProcess);
+    const bool initialSyncFlag =
+        replProcess->getConsistencyMarkers()->getInitialSyncFlag(startupOpCtx.get());
+
     // Assert that the in-memory featureCompatibilityVersion parameter has been explicitly set. If
     // we are part of a replica set and are started up with no data files, we do not set the
     // featureCompatibilityVersion until a primary is chosen. For this case, we expect the in-memory
-    // featureCompatibilityVersion parameter to still be uninitialized until after startup.
-    if (canCallFCVSetIfCleanStartup && (!replSettings.usingReplSets() || nonLocalDatabases)) {
+    // featureCompatibilityVersion parameter to still be uninitialized until after startup. If the
+    // initial sync flag is set and we are part of a replica set, we expect the version to be
+    // initialized as part of initial sync after startup.
+    const bool initializeFCVAtInitialSync = replSettings.usingReplSets() && initialSyncFlag;
+    if (canCallFCVSetIfCleanStartup && (!replSettings.usingReplSets() || nonLocalDatabases) &&
+        !initializeFCVAtInitialSync) {
         invariant(serverGlobalParams.featureCompatibility.isVersionInitialized());
     }