SERVER-42869 use shared_ptr to manage side writes counter in IndexBuildInterceptor

1 files changed, 8 insertions, 1 deletions

diff --git a/src/mongo/db/index/index_build_interceptor.h b/src/mongo/db/index/index_build_interceptor.h
index a9b36131ed5..4bdaaebf6f0 100644
--- a/src/mongo/db/index/index_build_interceptor.h
+++ b/src/mongo/db/index/index_build_interceptor.h
@@ -29,6 +29,8 @@
 
 #pragma once
 
+#include <memory>
+
 #include "mongo/db/index/duplicate_key_tracker.h"
 #include "mongo/db/index/index_access_method.h"
 #include "mongo/db/index/multikey_paths.h"
@@ -155,7 +157,12 @@ private:
 
     int64_t _numApplied{0};
 
-    AtomicWord<long long> _sideWritesCounter{0};
+    // This allows the counter to be used in a RecoveryUnit rollback handler where the
+    // IndexBuildInterceptor is no longer available (e.g. due to index build cleanup). If there are
+    // additional fields that have to be referenced in commit/rollback handlers, this counter should
+    // be moved to a new IndexBuildsInterceptor::InternalState structure that will be managed as a
+    // shared resource.
+    std::shared_ptr<AtomicWord<long long>> _sideWritesCounter;
 
     mutable stdx::mutex _multikeyPathMutex;
     boost::optional<MultikeyPaths> _multikeyPaths;