SERVER-31979 Include chunk migration statistics in moveChunk.commit in changelog

5 files changed, 18 insertions, 8 deletions

diff --git a/src/mongo/db/s/migration_chunk_cloner_source.h b/src/mongo/db/s/migration_chunk_cloner_source.h
index ff3d31132fa..75dd433c702 100644
--- a/src/mongo/db/s/migration_chunk_cloner_source.h
+++ b/src/mongo/db/s/migration_chunk_cloner_source.h
@@ -93,9 +93,12 @@ public:
      * This must only be called once and no more methods on the cloner must be used afterwards
      * regardless of whether it succeeds or not.
      *
+     * Returns statistics about the move. These are informational only and should not be
+     * interpreted by the caller for any means other than reporting.
+     *
      * NOTE: Must be called without any locks.
      */
-    virtual Status commitClone(OperationContext* opCtx) = 0;
+    virtual StatusWith<BSONObj> commitClone(OperationContext* opCtx) = 0;
 
     /**
      * Tells the recipient to abort the clone and cleanup any unused data. This method's
diff --git a/src/mongo/db/s/migration_chunk_cloner_source_legacy.cpp b/src/mongo/db/s/migration_chunk_cloner_source_legacy.cpp
index 42bb184d83a..18a73342a39 100644
--- a/src/mongo/db/s/migration_chunk_cloner_source_legacy.cpp
+++ b/src/mongo/db/s/migration_chunk_cloner_source_legacy.cpp
@@ -334,7 +334,7 @@ Status MigrationChunkClonerSourceLegacy::awaitUntilCriticalSectionIsAppropriate(
     return {ErrorCodes::ExceededTimeLimit, "Timed out waiting for the cloner to catch up"};
 }
 
-Status MigrationChunkClonerSourceLegacy::commitClone(OperationContext* opCtx) {
+StatusWith<BSONObj> MigrationChunkClonerSourceLegacy::commitClone(OperationContext* opCtx) {
     invariant(_state == kCloning);
     invariant(!opCtx->lockState()->isLocked());
 
@@ -348,7 +348,8 @@ Status MigrationChunkClonerSourceLegacy::commitClone(OperationContext* opCtx) {
                     "destination shard finished committing but there are still some session "
                     "metadata that needs to be transferred"};
         }
-        return Status::OK();
+
+        return responseStatus;
     }
 
     cancelClone(opCtx);
diff --git a/src/mongo/db/s/migration_chunk_cloner_source_legacy.h b/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
index 1bdad9ee4c7..3755a8b37ad 100644
--- a/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
+++ b/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
@@ -68,7 +68,7 @@ public:
     Status awaitUntilCriticalSectionIsAppropriate(OperationContext* opCtx,
                                                   Milliseconds maxTimeToWait) override;
 
-    Status commitClone(OperationContext* opCtx) override;
+    StatusWith<BSONObj> commitClone(OperationContext* opCtx) override;
 
     void cancelClone(OperationContext* opCtx) override;
 
diff --git a/src/mongo/db/s/migration_source_manager.cpp b/src/mongo/db/s/migration_source_manager.cpp
index 5ed5f2e66b6..f4325d74466 100644
--- a/src/mongo/db/s/migration_source_manager.cpp
+++ b/src/mongo/db/s/migration_source_manager.cpp
@@ -360,7 +360,7 @@ Status MigrationSourceManager::commitChunkOnRecipient(OperationContext* opCtx) {
     auto scopedGuard = MakeGuard([&] { cleanupOnError(opCtx); });
 
     // Tell the recipient shard to fetch the latest changes.
-    Status commitCloneStatus = _cloneDriver->commitClone(opCtx);
+    auto commitCloneStatus = _cloneDriver->commitClone(opCtx);
 
     if (MONGO_FAIL_POINT(failMigrationCommit) && commitCloneStatus.isOK()) {
         commitCloneStatus = {ErrorCodes::InternalError,
@@ -368,10 +368,11 @@ Status MigrationSourceManager::commitChunkOnRecipient(OperationContext* opCtx) {
     }
 
     if (!commitCloneStatus.isOK()) {
-        return {commitCloneStatus.code(),
-                str::stream() << "commit clone failed due to " << commitCloneStatus.toString()};
+        return commitCloneStatus.getStatus().withContext("commit clone failed");
     }
 
+    _recipientCloneCounts = commitCloneStatus.getValue()["counts"].Obj().getOwned();
+
     _state = kCloneCompleted;
     scopedGuard.Dismiss();
     return Status::OK();
@@ -575,7 +576,9 @@ Status MigrationSourceManager::commitChunkMetadataOnConfig(OperationContext* opC
                     BSON("min" << _args.getMinKey() << "max" << _args.getMaxKey() << "from"
                                << _args.getFromShardId()
                                << "to"
-                               << _args.getToShardId()),
+                               << _args.getToShardId()
+                               << "counts"
+                               << _recipientCloneCounts),
                     ShardingCatalogClient::kMajorityWriteConcern)
         .ignore();
 
diff --git a/src/mongo/db/s/migration_source_manager.h b/src/mongo/db/s/migration_source_manager.h
index d6a6df981c0..e052e6b95b3 100644
--- a/src/mongo/db/s/migration_source_manager.h
+++ b/src/mongo/db/s/migration_source_manager.h
@@ -242,6 +242,9 @@ private:
     // The transition from false to true is protected by the collection X-lock, which happens just
     // before the config server metadata commit is scheduled.
     bool _readsShouldWaitOnCritSec{false};
+
+    // The statistics about a chunk migration to be included in moveChunk.commit
+    BSONObj _recipientCloneCounts;
 };
 
 }  // namespace mongo