SERVER-29400 Make OplogFetcher and CollectionCloner batchSize configurable

1 files changed, 7 insertions, 1 deletions

diff --git a/src/mongo/db/repl/database_cloner.cpp b/src/mongo/db/repl/database_cloner.cpp
index 30e5f087a3d..0ebaf66e098 100644
--- a/src/mongo/db/repl/database_cloner.cpp
+++ b/src/mongo/db/repl/database_cloner.cpp
@@ -59,6 +59,11 @@ const char* kNameFieldName = "name";
 const char* kOptionsFieldName = "options";
 const char* kInfoFieldName = "info";
 const char* kUUIDFieldName = "uuid";
+// 16MB max batch size / 12 byte min doc size * 10 (for good measure) = defaultBatchSize to use.
+const auto defaultBatchSize = (16 * 1024 * 1024) / 12 * 10;
+
+// The batchSize to use for the find/getMore queries called by the CollectionCloner
+MONGO_EXPORT_STARTUP_SERVER_PARAMETER(collectionClonerBatchSize, int, defaultBatchSize);
 
 // The number of attempts for the listCollections commands.
 MONGO_EXPORT_SERVER_PARAMETER(numInitialSyncListCollectionsAttempts, int, 3);
@@ -358,7 +363,8 @@ void DatabaseCloner::_listCollectionsCallback(const StatusWith<Fetcher::QueryRes
                 options,
                 stdx::bind(
                     &DatabaseCloner::_collectionClonerCallback, this, stdx::placeholders::_1, nss),
-                _storageInterface);
+                _storageInterface,
+                collectionClonerBatchSize);
         } catch (const UserException& ex) {
             _finishCallback_inlock(lk, ex.toStatus());
             return;