SERVER-61026 Invert order of shards receiving drop collection participant command

2 files changed, 12 insertions, 7 deletions

diff --git a/src/mongo/db/s/drop_collection_coordinator.cpp b/src/mongo/db/s/drop_collection_coordinator.cpp
index fd5fb691b02..5caf5edca7f 100644
--- a/src/mongo/db/s/drop_collection_coordinator.cpp
+++ b/src/mongo/db/s/drop_collection_coordinator.cpp
@@ -198,8 +198,6 @@ ExecutorFuture<void> DropCollectionCoordinator::_runImpl(
                 _doc = _updateSession(opCtx, _doc);
 
                 const auto primaryShardId = ShardingState::get(opCtx)->shardId();
-                sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
-                    opCtx, nss(), {primaryShardId}, **executor, getCurrentSession(_doc));
 
                 // We need to send the drop to all the shards because both movePrimary and
                 // moveChunk leave garbage behind for sharded collections.
@@ -212,6 +210,12 @@ ExecutorFuture<void> DropCollectionCoordinator::_runImpl(
                 sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
                     opCtx, nss(), participants, **executor, getCurrentSession(_doc));
 
+                // The sharded collection must be dropped on the primary shard after it has been
+                // dropped on all of the other shards to ensure it can only be re-created as
+                // unsharded with a higher optime than all of the drops.
+                sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
+                    opCtx, nss(), {primaryShardId}, **executor, getCurrentSession(_doc));
+
                 ShardingLogging::get(opCtx)->logChange(opCtx, "dropCollection", nss().ns());
                 LOGV2(5390503, "Collection dropped", "namespace"_attr = nss());
             }))
diff --git a/src/mongo/db/s/drop_database_coordinator.cpp b/src/mongo/db/s/drop_database_coordinator.cpp
index 26fba5a99f0..70a79970fe2 100644
--- a/src/mongo/db/s/drop_database_coordinator.cpp
+++ b/src/mongo/db/s/drop_database_coordinator.cpp
@@ -138,11 +138,6 @@ void DropDatabaseCoordinator::_dropShardedCollection(
     const auto primaryShardId = ShardingState::get(opCtx)->shardId();
     _doc = _updateSession(opCtx, _doc);
 
-    // The collection needs to be dropped first on the db primary shard
-    // because otherwise changestreams won't receive the drop event.
-    sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
-        opCtx, nss, {primaryShardId}, **executor, getCurrentSession(_doc));
-
     // We need to send the drop to all the shards because both movePrimary and
     // moveChunk leave garbage behind for sharded collections.
     auto participants = Grid::get(opCtx)->shardRegistry()->getAllShardIds(opCtx);
@@ -151,6 +146,12 @@ void DropDatabaseCoordinator::_dropShardedCollection(
                        participants.end());
     sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
         opCtx, nss, participants, **executor, getCurrentSession(_doc));
+
+    // The sharded collection must be dropped on the primary shard after it has been dropped on all
+    // of the other shards to ensure it can only be re-created as unsharded with a higher optime
+    // than all of the drops.
+    sharding_ddl_util::sendDropCollectionParticipantCommandToShards(
+        opCtx, nss, {primaryShardId}, **executor, getCurrentSession(_doc));
 }
 
 DropDatabaseCoordinator::DropDatabaseCoordinator(ShardingDDLCoordinatorService* service,