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[TRTLLM-16720][fix] Bound remote MPI failures and launcher shutdown - #19664
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WalkthroughThe MPI server now processes task batches in order and bounds shutdown. The launcher and disaggregated leader use process guards to supervise child process groups. New regression tests cover server, launcher, multi-rank, and leader lifecycle behavior. ChangesMPI lifecycle and process supervision
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~60 minutes Change: Bug fix Merge Risk: 🔵 Low · up to This change bounds MPI server and launcher shutdown and adds process supervision. The remaining issue affects only the tests: one lifecycle test leaks proxy-mode environment variables into later tests in the same worker, which can make CPU CI results depend on test order. The fix is small, and the change is otherwise mergeable. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 17.69% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 130 functions across 12 files. (3 skipped: 3 unsupported.)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Review comments at @tensorrt_llm/llmapi/trtllm-llmapi-launch:
- Around line 302-311: Update the shutdown wait loop around stop_pid to reap the
stop helper as soon as it exits; if it exits nonzero, preserve task_exit_code
precedence and return stop_exit_code instead of waiting for the shutdown
timeout. Track whether the helper was reaped so the later wait does not reap it
again, allowing cleanup_launcher to terminate the server.
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📒 Files selected for processing (10)
tensorrt_llm/llmapi/mgmn_leader_node.pytensorrt_llm/llmapi/mpi_session.pytensorrt_llm/llmapi/trtllm-llmapi-launchtests/integration/test_lists/test-db/l0_cpu.ymltests/unittest/executor/test_proxy_fast_death.pytests/unittest/llmapi/_run_mpi_lifecycle_task.pytests/unittest/llmapi/test_mpi_launcher_shutdown.pytests/unittest/llmapi/test_mpi_lifecycle.pytests/unittest/llmapi/test_mpi_server_lifecycle.pytests/unittest/llmapi/test_mpi_session.py
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- tests/unittest/executor/test_proxy_fast_death.py
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chienchunhung
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Approving — the comments below are optional touch-ups, not blockers.
All six concerns from the previous round are addressed in the current head, five in code and one by documentation:
- All-ranks-fail server exit: the serve loop holds the
RemoteWorkerDeathchannel open until stop or the original deadline ([mpi_session.py:1075](https://github.com/NVIDIA/TensorRT-LLM/pull/19664/files#diff-f638c9123dac642a31a634a9f4b0d4a27087446370c805285d2f7e8ea2a8256aR1075)-1079), andtest_mpi_lifecycle.pyall_failureasserts bothRank0 Task exit code: 23and that "MPI Comm server exited before the task" does not appear. - Server-first exit losing the task status:
trtllm-llmapi-launch:382-407waits up to the stop timeout for natural task exit and lets a nonzero task status win. $SECONDSgranularity: gone from the launcher; all three waits count 100 ms sleeps.- Launcher-SIGKILL orphaning: covered by the guard's PDEATHSIG plus getppid polling, with the owner-death tests.
- Timeout coupling between
TLLM_MGMN_SHUTDOWN_GRACE_SECONDSandTLLM_LLMAPI_LAUNCH_STOP_TIMEOUT: accepted as documented rather than derived; fine for this round.
Approving. The items below are non-blocking.
Branch target. This is ~3000 lines including a new supervisor script, landing directly on release/1.3. Is there a main counterpart open or planned? Release branches normally receive cherry-picks, and this will otherwise regress on the next release cut.
Description omissions. Two behavior changes worth a line each: the stop helper now exits nonzero via ClickException with a 5 s send timeout instead of logging and returning 0 ([mgmn_leader_node.py:56](https://github.com/NVIDIA/TensorRT-LLM/pull/19664/files#diff-87423f1df82083d13b2841f6c897f5933d39446849799fcaedb01adb1ecb5302R56)), and the disaggregated leader no longer SIGKILLs the guard after the 30 s terminate timeout; it raises and leaves the guard owning the proxy group ([serve.py:2720](https://github.com/NVIDIA/TensorRT-LLM/pull/19664/files#diff-d4dc7bcbaafe6618504eda2c223901b6e0910f740c04e2c3390cb26c48dcd68bR2720)).
Residual timing in the launcher tests. With TLLM_LLMAPI_LAUNCH_STOP_TIMEOUT=1, test_launcher_deadline_covers_stop_helper_and_server still needs three sequential interpreter startups (stub, guard, payload stub) to each land inside a ~1 s poll budget before it asserts that stop ran. Much better than the near-zero window before, but a loaded CPU node can still miss it. Raising the default in _launcher_env to 3 (as server_exits_naturally already does) would cost two seconds per timeout test and remove the risk.
CPU stage cost. See the inline note on l0_cpu.yml: the real-MPI lifecycle file adds roughly ten minutes to pre-merge CPU and skips silently without an MPI runtime.
Signed-off-by: Chien-Chun Hung <2679986+chienchunhung@users.noreply.github.com>
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A main counterpart is planned after this release fix is finalized. I’ll reuse the executor cleanup merged in #19456, coordinate the overlapping work in #19660, and link the counterpart here. The description now documents the stop helper’s status-1 failure and five-second send timeout, plus retention of the proxy guard after the 30-second cleanup wait. Existing exceptions are preserved; otherwise, cleanup raises RuntimeError. I raised the launcher fixture timeout to three seconds and its outer watchdog to 15 seconds, while keeping the one-second clock-boundary coverage. All 46 local launcher tests passed in 101.9 seconds, compared with 80.7 seconds previously. Both checks with a 1.5-second startup delay passed with the new budget and failed with the old budget. I also reduced the L0 MPI lifecycle selection to seven cases per architecture; all 20 remain available on demand. Earlier CI executed all 18 cases then present on both architectures without skips. The reduced selection’s runtime still needs measurement. |
Skip cleanup grace after failed process-group setup while retaining child and group termination and reaping. Keep seven real-MPI lifecycle cases in L0, with the complete file available for on-demand verification. Give launcher tests more startup margin while preserving one-second boundary coverage and bounded outer waits. Signed-off-by: Chien-Chun Hung <2679986+chienchunhung@users.noreply.github.com>
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juney-nvidia
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Approved from OSS compliance perspective.
11 participants
Summary
Remote MPI failures could block shutdown, hide task errors, or leave child processes alive after launcher death. This change bounds teardown, preserves worker diagnostics and process ownership, and removes the synchronous polling delay implicated in NVBUG 6783891, targeting
release/1.3.Scope
Future.exception()so storedSystemExitandKeyboardInterruptreach clients; server-local interrupts still propagate, synchronous responses keep their exception-object contract, synchronous polling loses the extra eight-second sleep, and final session/shared-pool teardown shares the remaining deadline while individual sessions remain reusable.IMMEDIATE=1, a five-second send timeout and one-second linger, raisingClickException/status 1 on send failure; startup/import time remains inside the launcher budget, outside the send timeout.finally; after a 30-second cleanup wait it leaves the guard owning the proxy group, preserves a pending exception, or raisesRuntimeErrorif none was pending.all_failure-2,worker_system_exit-2,mixed_collective-4,all_hang-2,reuse-2,sync_recovery-2, andasync_drain-2; the full file remains available on demand.The guide documents ordering, fatal-service behavior, cleanup limits and coupled production defaults: 60-second server grace, 120-second launcher stop timeout and five-second TERM grace. Invalid launcher settings return 2; task-first shutdown timeout returns 124 unless an earlier task failure takes precedence. Launcher test defaults now allow three seconds and a 15-second outer watchdog; the deliberate clock-boundary tests retain one second.
Verification
Final source:
d72176dd4a51f760bc1b5c85f41adf866c614eda. The checks below used the exact three-file change committed on top of81df412f44106bfad8cd27707e5fa814c1773725; source hashes match the published files. Required hooks passed, and a fresh review of the complete 16-file PR found no new actionable issue. Existing external review threads retain their separate resolution state.test_mpi_launcher_shutdown.pyThe launcher run used macOS ARM64, Python 3.13.11 and pytest 9.0.2, executing the real Bash launcher/stdlib guard with stand-in payloads:
PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 PYTEST_ADDOPTS='' python -m pytest -c /dev/null --noconftest -p no:cacheprovider -o 'markers=cpu_only: CPU-only supervision tests' tests/unittest/llmapi/test_mpi_launcher_shutdown.py -v --durations=10. Repository conftests/native imports were disabled. Logs, JUnit, controls, source hashes and review artifacts are retained inpr19664-brnguyen2-20261008andpr19664-publish-final-comments-20261008.The latest changes affect the stdlib guard, its standalone tests and test selection, so their targeted verification ran locally. Linux/native MPI and the reduced selection's actual CI runtime remain pending for this commit. Historical case timings estimate about 5.4 minutes on x86 and 5.7 minutes on ARM for the reduced selection; these are estimates, not a measured new run. Earlier 18-case executions measured 13.1/14.9 minutes on x86/ARM and passed without skips.
Full CI: release/1.3 run #112 started on
d72176dd4a51f760bc1b5c85f41adf866c614edaat 2026-10-09 01:47:45 UTC. Launch parameters confirm all stages (stage_list=null), tests enabled (skip_test=false), fail-fast disabled, and no prior test build reused. Test results are pending; trigger request.Earlier evidence, attributed to its tested revision
81df412f44106bfad8cd27707e5fa814c1773725completed FAILURE, as confirmed by the CI bot. The available stage metadata reports an SBSA single-GPU downstream failure and a blocked SBSA multi-GPU stage; the test-level cause has not yet been verified.81df412f44106bfad8cd27707e5fa814c1773725, 51 targeted cases passed: 42 server lifecycle, three real-ZMQ synchronous response and six real-MPI cases (worker_system_exit,all_failure,sync_recovery, each at two/four ranks). Five pre-change SystemExit controls failed as expected; the two new real-MPI worker-exit cases delivered diagnostics after a 5.1-second delayed client poll, preserved status 24, and left no live descendants. The six MPI cases took 206.45 seconds.ipp2-2033, eight CPUs, a 20-GiB container cap, NGC 26.08 / CI62540 TensorRT-LLM 1.4.0rc0 (compiled sourcef013786b334274747bf9e0639ffe04d480f8cdbc), Open MPI 5.0.10rc2 and mpi4py 3.1.5 with exact Python overlays. One allocated H100 was visible for imports; tests were model-free. It was compatible-runtime evidence, not a fresh release build; the allocation was released. Run artifacts:pr19664-h8-20261008.e0f8bc1c371398161c09ae2429c039fd7adcdddc, full release/1.3 CI #81 passed. The preceding ARM snapshot also passed 118 distinct cases and six MPI 5 compatibility repetitions; its full 18-case MPI suite took 630.27 seconds on TensorRT-LLM 1.3.0rc1 / Open MPI 4.1.9a1. Two pre-fix disaggregated controls left descendants alive; all 12 guarded cases passed (os._exitrepresented nonreturning abort in those controls).7fd987886ea080d10a0ebf8992303af8bb95cf2d, all four original NVBUG variants passed three rounds under the original 60-second watchdog. Instrumentation measured about 16 seconds of removed polling delay. The original intermittent timeout was not reproduced deterministically, so these results do not establish complete NVBUG closure.Notes
Supersedes #19660's workaround for #19659. Includes the shared-executor cleanup helper and four tests from merged #19456 needed on
release/1.3; unrelated warmup changes are excluded.A separate
maincounterpart is planned after this release fix is finalized. It will reuse the cleanup already merged in #19456, reconcile the overlapping #19660 work, check current main's supported disaggregated paths, and receive independent review and verification. No counterpart PR is open yet; its link will be added here.