SERVER-59811 Fix afterClusterTime in ReshardingOplogFetcher.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/mongo/db/s/resharding/resharding_oplog_fetcher.cpp b/src/mongo/db/s/resharding/resharding_oplog_fetcher.cpp
index e04cf21ef44..a4d7bb20352 100644
--- a/src/mongo/db/s/resharding/resharding_oplog_fetcher.cpp
+++ b/src/mongo/db/s/resharding/resharding_oplog_fetcher.cpp
@@ -255,8 +255,12 @@ AggregateCommandRequest ReshardingOplogFetcher::_makeAggregateCommandRequest(
     AggregateCommandRequest aggRequest(NamespaceString::kRsOplogNamespace,
                                        std::move(serializedPipeline));
     if (_useReadConcern) {
+        // We specify {afterClusterTime: <highest _id.clusterTime>, level: "majority"} as the read
+        // concern to guarantee the postBatchResumeToken when the batch is empty is non-decreasing.
+        // The ReshardingOplogFetcher depends on inserting documents in increasing _id order,
+        // including for the synthetic no-op oplog entries generated from the postBatchResumeToken.
         auto readConcernArgs = repl::ReadConcernArgs(
-            boost::optional<LogicalTime>(_startAt.getTs()),
+            boost::optional<LogicalTime>(_startAt.getClusterTime()),
             boost::optional<repl::ReadConcernLevel>(repl::ReadConcernLevel::kMajorityReadConcern));
         aggRequest.setReadConcern(readConcernArgs.toBSONInner());
     }