Fix flaky DataLoaderPerformanceTest with deterministic synchronization#4299
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The "expensive query" tests with multiple root fields (shops + expensiveShops) were flaky because random-sleep async data fetchers could complete at different times, causing ExhaustedDataLoaderDispatchStrategy to dispatch prematurely and split batches. Uses a two-latch synchronization approach: 1. Root fetcher rendezvous: ensures both root data fetchers complete simultaneously 2. Completion overlap latch: ensures both root fields are inside their startComplete/stopComplete window before either proceeds, eliminating the race between thenApply callbacks entirely Also removes @ignore from the equivalent test in DataLoaderPerformanceWithChainedInstrumentationTest and tightens assertions from <= 2 to == 1 since synchronized fetching guarantees optimal batching. Co-Authored-By: Claude Opus 4.6 <[email protected]>
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andimarek
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Mar 8, 2026
Add 8 deterministic tests that directly exercise the concurrent state machine in ExhaustedDataLoaderDispatchStrategy, recovering branch and line coverage lost when PR #4299 replaced race-condition-dependent timing with deterministic latch-based synchronization. Tests cover: - Basic dispatch cycle (finishedFetching triggers dispatch) - Early return in newDataLoaderInvocation when flag already set - Dispatch from newDataLoaderInvocation when objectRunningCount is 0 - Multiple dispatch rounds with chained data loader invocations - executionSerialStrategy state reset - Subscription alternative call context with separate call stack - startComplete/stopComplete dispatch coordination - Deferred call context lazy call stack creation via computeIfAbsent https://claude.ai/code/session_01WwTVwjXS1wakJQmZYsXLvY
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Summary
DataLoaderPerformanceTestandDataLoaderPerformanceWithChainedInstrumentationTestthat intermittently failed withdepartmentsForShopsBatchLoaderCounter > 2shops/expensiveShops) completing at different times causedExhaustedDataLoaderDispatchStrategyto dispatch prematurely, splitting what should be a single batch into multiple batchesBatchCompareDataFetchers:CountDownLatch): ensures both root data fetchers complete simultaneously on a dedicated thread poolCountDownLatch): ensures both root fields are inside theirstartComplete/stopCompletewindow before either proceeds, fully eliminating the race betweenthenApplycallbacks@Ignorefrom the equivalent chained instrumentation test that was disabled for the same flakiness<= 2to== 1since synchronized fetching guarantees optimal batchingTest plan
@Ignored test)🤖 Generated with Claude Code