Impact

Resharding C++ tests can hang in shutdownExecutorPool() or hit teardown-time invariants when the test exits with a donor, recipient, or coordinator PrimaryOnlyService instance that has not fully completed.

Related failures include BF-43436, BF-43491, BF-43612, and BF-44484.

Root Cause

ReshardingCoordinatorServiceTestCommon::tearDown() never steps down the coordinator instances, and it calls _registry->onShutdown() only after ConfigServerTestFixture::tearDown(). That base teardown shuts down the executor pool, ShardRegistry and CatalogCache, and clears ShardingCatalogManager and Grid, so coordinators can keep running against torn-down sharding state. ReshardingDonorRecipientCommonTest already uses the correct order: step down, shut down executors, join instances, then tear down the fixture. Its per-test interrupt() calls are redundant.

Fix

Make each fixture responsible for fully quiescing the state machines it creates.

• In the coordinator fixture: step down, shut down the executor pool, then call onShutdown() before ConfigServerTestFixture::tearDown(). Remove the redundant per-test interrupt() calls.
• Do not require individual test bodies to interrupt or run state machines to completion solely for safe fixture teardown.

Testing

• Run ProcessDonorFields* tests without per-test cleanup and verify teardown completes.
• Run CreateRecipientServiceInstance without its per-test interrupt() and verify teardown neither hangs nor triggers the recipient state-transition invariant.
• Add a coordinator test that returns while a mock fetch is blocked, without explicitly calling stepDown() or completing resharding.
• Repeat the affected tests under TSAN to exercise teardown races.

Related

• SERVER-127727
• SERVER-128091
• SERVER-131477
• SERVER-132461
• BF-43436
• BF-43491
• BF-43612
• BF-44484