SERVER-41986 add handling of unfinished indexes due to shutdown

Author: benety

src/mongo/db/index_builds_coordinator.cpp

@@ -806,11 +806,20 @@ void IndexBuildsCoordinator::_runIndexBuildInner(OperationContext* opCtx,
         status = ex.toStatus();
     }
 
-    if (replSetAndNotPrimary && status == ErrorCodes::InterruptedAtShutdown) {
+    if (status == ErrorCodes::InterruptedAtShutdown) {
         // Leave it as-if kill -9 happened. This will be handled on restart.
         _indexBuildsManager.interruptIndexBuild(opCtx, replState->buildUUID, "shutting down");
-        replState->stats.numIndexesAfter = replState->stats.numIndexesBefore;
-        status = Status::OK();
+
+        // On secondaries, a shutdown interruption status is part of normal operation and
+        // should be suppressed, unlike other errors which should be raised to the administrator's
+        // attention via a server crash. The server will attempt to recover the index build during
+        // the next startup.
+        // On primary and standalone nodes, the failed index build will not be replicated so it is
+        // okay to propagate the shutdown error to the client.
+        if (replSetAndNotPrimary) {
+            replState->stats.numIndexesAfter = replState->stats.numIndexesBefore;
+            status = Status::OK();
+        }
     } else if (IndexBuildProtocol::kTwoPhase == replState->protocol) {
         // TODO (SERVER-40807): disabling the following code for the v4.2 release so it does not
         // have downstream impact.