next.js

ad93e452 - Fix telemetry event loss on build failures and server shutdown (#85867)

Fix telemetry event loss on build failures and server shutdown (#85867) ## Problem Telemetry events were not being captured in three scenarios: ### 1. MCP Telemetry Lost on Dev Server Shutdown Two telemetry instances were created during dev server startup. MCP events were recorded to one instance but shutdown flushed a different instance. **Fix:** Reuse the existing telemetry instance from `traceGlobals`. ### 2. Process Exit Timeout Killing Async Telemetry The CLI force-kills child processes after 100ms (`NEXT_EXIT_TIMEOUT_MS`). Async telemetry operations were interrupted before completion. **Fix:** Use `flushDetached()` to write events to disk and spawn a detached process for async submission, allowing immediate parent exit. ### 3. Build Errors Calling `process.exit()` Before Telemetry Flush `process.exit()` calls in error handlers (SWC failures, missing dependencies, route conflicts) bypassed finally blocks and killed processes before telemetry completed. **Fix:** Throw errors instead of calling `process.exit()`, add finally blocks with `await telemetry.flush()` in critical paths. ## Changes **Core:** - `server/dev/next-dev-server.ts`: Reuse telemetry instance - `server/lib/start-server.ts`: Use `flushDetached()` for shutdown - `build/swc/index.ts`: Remove `process.exit()` calls - `build/turbopack-build/impl.ts`: Add telemetry flush in worker finally block - `build/index.ts`: Add telemetry flush in finally block, throw instead of exit - `lib/verify-partytown-setup.ts`: Throw instead of exit **Supporting:** - `telemetry/storage.ts`: Generate unique event files per PID - `telemetry/detached-flush.ts`: Accept optional eventsFile parameter - `errors.json`: Update detached-flush error message ## Testing All telemetry tests now pass: - MCP telemetry on dev server shutdown - SWC load failures in worker threads - Build configuration errors ✅ Non-blocking shutdown ✅ Timeout-independent ✅ No race conditions ✅ Works in worker threads