SERVER-41988 ignore prepare conflicts on secondaries

(cherry picked from commit 51f76f553c696ebd6d6bb90a97ab66d8b1510a31)

1 files changed, 8 insertions, 0 deletions

diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index 1d4a7e05906..d7d2a75f3c0 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -1028,6 +1028,14 @@ Status multiSyncApply(OperationContext* opCtx,
     // Explicitly start future read transactions without a timestamp.
     opCtx->recoveryUnit()->setTimestampReadSource(RecoveryUnit::ReadSource::kNoTimestamp);
 
+    // When querying indexes, we return the record matching the key if it exists, or an adjacent
+    // document. This means that it is possible for us to hit a prepare conflict if we query for an
+    // incomplete key and an adjacent key is prepared.
+    // We ignore prepare conflicts on secondaries because they may encounter prepare conflicts that
+    // did not occur on the primary.
+    opCtx->recoveryUnit()->setPrepareConflictBehavior(
+        PrepareConflictBehavior::kIgnoreConflictsAllowWrites);
+
     ApplierHelpers::stableSortByNamespace(ops);
 
     // Assume we are recovering if oplog writes are disabled in the options.