SERVER-62849 Drain recoverable RefineCollectionShardKeyCoordinators on FCV downgrade

1 files changed, 13 insertions, 0 deletions

diff --git a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
index aae37683145..540d8657f6f 100644
--- a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
+++ b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
@@ -80,6 +80,7 @@
 #include "mongo/logv2/log.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/pm2423_feature_flags_gen.h"
+#include "mongo/s/refine_collection_shard_key_coordinator_feature_flags_gen.h"
 #include "mongo/s/resharding/resharding_feature_flag_gen.h"
 #include "mongo/stdx/unordered_set.h"
 #include "mongo/util/exit.h"
@@ -397,6 +398,18 @@ public:
                             opCtx, DDLCoordinatorTypeEnum::kCollMod);
                 }
 
+                // TODO SERVER-62850 Remove when 6.0 branches-out
+                if (actualVersion > requestedVersion &&
+                    !feature_flags::gFeatureFlagRecoverableRefineCollectionShardKeyCoordinator
+                         .isEnabledOnVersion(requestedVersion)) {
+                    // No more (recoverable) ReshardCollectionCoordinators will start because we
+                    // have already switched the FCV value to kDowngrading. Wait for the ongoing
+                    // RefineCollectionCoordinators to finish.
+                    ShardingDDLCoordinatorService::getService(opCtx)
+                        ->waitForCoordinatorsOfGivenTypeToComplete(
+                            opCtx, DDLCoordinatorTypeEnum::kRefineCollectionShardKey);
+                }
+
                 // If we are only running phase-1, then we are done
                 return true;
             }