SERVER-38891 Fix some `collection_cloner_test` races.

The mocks in these tests hold pointers to items on the stack.  The
mocks are held in background threads, such as executors.  If the
executor accesses one of those mocks after the stack frame of its
creator leaves, the pointer to the stack frame is now invalid.

1 files changed, 10 insertions, 9 deletions

diff --git a/src/mongo/db/repl/databases_cloner_test.cpp b/src/mongo/db/repl/databases_cloner_test.cpp
index 4340c0a8d51..7463f93ab7c 100644
--- a/src/mongo/db/repl/databases_cloner_test.cpp
+++ b/src/mongo/db/repl/databases_cloner_test.cpp
@@ -1,4 +1,3 @@
-
 /**
  *    Copyright (C) 2018-present MongoDB, Inc.
  *
@@ -66,7 +65,7 @@ using namespace unittest;
 using Responses = std::vector<std::pair<std::string, BSONObj>>;
 
 struct CollectionCloneInfo {
-    CollectionMockStats stats;
+    std::shared_ptr<CollectionMockStats> stats = std::make_shared<CollectionMockStats>();
     CollectionBulkLoaderMock* loader = nullptr;
     Status status{ErrorCodes::NotYetInitialized, ""};
 };
@@ -176,18 +175,20 @@ protected:
             [this](const NamespaceString& nss,
                    const CollectionOptions& options,
                    const BSONObj idIndexSpec,
-                   const std::vector<BSONObj>& secondaryIndexSpecs) {
+                   const std::vector<BSONObj>& secondaryIndexSpecs)
+            -> StatusWith<std::unique_ptr<CollectionBulkLoaderMock>> {
                 // Get collection info from map.
                 const auto collInfo = &_collections[nss];
-                if (collInfo->stats.initCalled) {
+                if (collInfo->stats->initCalled) {
                     log() << "reusing collection during test which may cause problems, ns:" << nss;
                 }
-                (collInfo->loader = new CollectionBulkLoaderMock(&collInfo->stats))
-                    ->init(secondaryIndexSpecs)
-                    .transitional_ignore();
+                auto localLoader = std::make_unique<CollectionBulkLoaderMock>(collInfo->stats);
+                auto status = localLoader->init(secondaryIndexSpecs);
+                if (!status.isOK())
+                    return status;
+                collInfo->loader = localLoader.get();
 
-                return StatusWith<std::unique_ptr<CollectionBulkLoader>>(
-                    std::unique_ptr<CollectionBulkLoader>(collInfo->loader));
+                return std::move(localLoader);
             };
 
         _dbWorkThreadPool.startup();