From 63ffb50b2889c9d60a506dc0e8a1071c3ac39e36 Mon Sep 17 00:00:00 2001
From: Josef Ahmad <josef.ahmad@mongodb.com>
Date: Fri, 5 May 2023 09:21:15 +0000
Subject: [PATCH] SERVER-74953 reproducer

---
 jstests/noPassthrough/repro-server-74953.js | 51 +++++++++++++++++++++
 src/mongo/db/index_builds_coordinator.cpp   |  4 ++
 2 files changed, 55 insertions(+)
 create mode 100644 jstests/noPassthrough/repro-server-74953.js

diff --git a/jstests/noPassthrough/repro-server-74953.js b/jstests/noPassthrough/repro-server-74953.js
new file mode 100644
index 00000000000..b04820f9a6b
--- /dev/null
+++ b/jstests/noPassthrough/repro-server-74953.js
@@ -0,0 +1,51 @@
+/**
+ * Starts an index build, simulating a slow setup condition, and steps down the primary. If the
+ * startIndexBuild has not yet been replicated, the build should be killed while stepping down.
+ * Otherwise, we are in an inconsistent state, where the new primary can drop the collection (which
+ * has no active builds) and cause the secondary to detect an active build before dropping the
+ * collection.
+ *
+ * @tags: [
+ *   requires_replication,
+ * ]
+ */
+(function() {
+'use strict';
+
+load('jstests/libs/fail_point_util.js');
+load('jstests/noPassthrough/libs/index_build.js');
+
+const rst = new ReplSetTest({nodes: 2});
+rst.startSet();
+rst.initiate();
+
+const primary = rst.getPrimary();
+const primaryDB = primary.getDB('test');
+const primaryColl = primaryDB.getCollection('coll');
+
+assert.commandWorked(primaryColl.insert({_id: 1, a: 1}));
+
+// Enable fail point which makes index build hang during setup, simulating a condition where the
+// index build is registered, but not yet replicated.
+const failPoint = configureFailPoint(primary, 'hangIndexBuildOnSetupBeforeTakingLocks');
+
+const createIndex = IndexBuildTest.startIndexBuild(
+    primary, primaryColl.getFullName(), {a: 1}, {}, [ErrorCodes.InterruptedDueToReplStateChange]);
+
+failPoint.wait();
+
+assert.commandWorked(primaryDB.adminCommand({"replSetStepDown": 5 * 60, "force": true}));
+
+const newPrimary = rst.getPrimary();
+const newPrimaryDB = newPrimary.getDB('test');
+const newPrimaryColl = newPrimaryDB.getCollection('coll');
+
+// Drop the collection on the new primary. If the index build on the old primary was not properly
+// aborted on step-down, the node will crash while applying the drop.
+newPrimaryColl.drop();
+
+rst.awaitReplication();
+createIndex();
+
+rst.stopSet();
+})();
diff --git a/src/mongo/db/index_builds_coordinator.cpp b/src/mongo/db/index_builds_coordinator.cpp
index 8051f89ec36..1ef869661de 100644
--- a/src/mongo/db/index_builds_coordinator.cpp
+++ b/src/mongo/db/index_builds_coordinator.cpp
@@ -95,6 +95,7 @@ MONGO_FAIL_POINT_DEFINE(hangBeforeUnregisteringAfterCommit);
 MONGO_FAIL_POINT_DEFINE(failSetUpResumeIndexBuild);
 MONGO_FAIL_POINT_DEFINE(failIndexBuildWithError);
 MONGO_FAIL_POINT_DEFINE(hangInRemoveIndexBuildEntryAfterCommitOrAbort);
+MONGO_FAIL_POINT_DEFINE(hangIndexBuildOnSetupBeforeTakingLocks);
 
 IndexBuildsCoordinator::IndexBuildsSSS::IndexBuildsSSS()
     : ServerStatusSection("indexBuilds"),
@@ -2301,6 +2302,9 @@ IndexBuildsCoordinator::PostSetupAction IndexBuildsCoordinator::_setUpIndexBuild
     std::shared_ptr<ReplIndexBuildState> replState,
     Timestamp startTimestamp,
     const IndexBuildOptions& indexBuildOptions) {
+
+    hangIndexBuildOnSetupBeforeTakingLocks.pauseWhileSet(opCtx);
+
     auto [dbLock, collLock, rstl] =
         std::move(_acquireExclusiveLockWithRSTLRetry(opCtx, replState.get()).getValue());
 
-- 
2.17.1