SERVER-36132 Invariant that chunk migration is actually reflected in the metadata after successful commit

(cherry picked from commit 4858e05ee6bb59ec728d74802766c05b122aeced)

1 files changed, 15 insertions, 1 deletions

diff --git a/src/mongo/db/s/migration_source_manager.cpp b/src/mongo/db/s/migration_source_manager.cpp
index 035d21cbb82..28c43545e94 100644
--- a/src/mongo/db/s/migration_source_manager.cpp
+++ b/src/mongo/db/s/migration_source_manager.cpp
@@ -413,7 +413,21 @@ Status MigrationSourceManager::commitChunkMetadataOnConfig(OperationContext* txn
         }
 
         if (refreshedMetadata->keyBelongsToMe(_args.getMinKey())) {
-            // The chunk modification was not applied, so report the original error
+            // This condition may only happen if the migration commit has failed for any reason
+            if (migrationCommitStatus.isOK()) {
+                severe() << "The migration commit succeeded, but the new chunk placement was not "
+                            "reflected after metadata refresh, which is an indication of an "
+                            "afterOpTime bug.";
+                severe() << "The current config server opTime is " << grid.configOpTime();
+                severe() << "The commit response contained:";
+                severe() << "  metadata: "
+                         << redact(commitChunkMigrationResponse.getValue().metadata.toString());
+                severe() << "  response: "
+                         << redact(commitChunkMigrationResponse.getValue().response.toString());
+
+                fassertFailed(50878);
+            }
+
             return {migrationCommitStatus.code(),
                     str::stream() << "Chunk move was not successful due to "
                                   << migrationCommitStatus.reason()};