SERVER-35050 Don't abort collection clone due to negative document count

(cherry picked from commit 5ed5b857aaf2e2fbf443588e9b4cbb359fbd1f4d)

2 files changed, 9 insertions, 8 deletions

diff --git a/src/mongo/db/repl/collection_cloner.cpp b/src/mongo/db/repl/collection_cloner.cpp
index 0cfb0eb46c0..ee3b0c78a9f 100644
--- a/src/mongo/db/repl/collection_cloner.cpp
+++ b/src/mongo/db/repl/collection_cloner.cpp
@@ -352,13 +352,13 @@ void CollectionCloner::_countCallback(
         }
     }
 
+    // The count command may return a negative value after an unclean shutdown,
+    // so we set it to zero here to avoid aborting the collection clone.
+    // Note that this count value is only used for reporting purposes.
     if (count < 0) {
-        _finishCallback({ErrorCodes::BadValue,
-                         str::stream() << "Count call on collection " << _sourceNss.ns() << " from "
-                                       << _source.toString()
-                                       << " returned negative document count: "
-                                       << count});
-        return;
+        warning() << "Count command returned negative value. Updating to 0 to allow progress "
+                     "meter to function properly. ";
+        count = 0;
     }
 
     {
diff --git a/src/mongo/db/repl/collection_cloner_test.cpp b/src/mongo/db/repl/collection_cloner_test.cpp
index 23a15426583..246e9f44d21 100644
--- a/src/mongo/db/repl/collection_cloner_test.cpp
+++ b/src/mongo/db/repl/collection_cloner_test.cpp
@@ -326,15 +326,16 @@ TEST_F(CollectionClonerTest, CollectionClonerReturnsNoSuchKeyOnMissingDocumentCo
     ASSERT_EQUALS(ErrorCodes::NoSuchKey, getStatus());
 }
 
-TEST_F(CollectionClonerTest, CollectionClonerReturnsBadValueOnNegativeDocumentCount) {
+TEST_F(CollectionClonerTest, CollectionClonerDoesNotAbortOnNegativeDocumentCount) {
     ASSERT_OK(collectionCloner->startup());
 
     {
         executor::NetworkInterfaceMock::InNetworkGuard guard(getNet());
         processNetworkResponse(createCountResponse(-1));
     }
+    getExecutor().shutdown();
     collectionCloner->join();
-    ASSERT_EQUALS(ErrorCodes::BadValue, getStatus());
+    ASSERT_EQUALS(0U, collectionCloner->getStats().documentToCopy);
 }
 
 class TaskExecutorWithFailureInScheduleRemoteCommand : public unittest::TaskExecutorProxy {