[sankalpsthakur]

Closes #644

Proposed Changes

Since Python 3.9, concurrent.futures shuts its thread pools down before atexit handlers run. The batching WriteApi schedules each write on a ThreadPoolScheduler, so from that point on the scheduler refuses the batch with RuntimeError: cannot schedule new futures after interpreter shutdown, and the batch is logged as failed and dropped. Closing the WriteApi from an atexit handler, as the README and examples/iot_sensor.py show, doesn't help: the flush_interval timer usually fires while the thread pools are shutting down, which is why the error in the issue is printed before closing.

This catches that error after the scheduling steps in _to_response and writes the batch on the current thread instead. Any other error is handled as before.

Behavior notes:

• A program that exits without closing the WriteApi now also gets its pending batch written instead of dropped. If InfluxDB is unreachable at that point, exit can take up to max_retry_time while the write is retried.
• On Python 3.7 and 3.8 the thread pools still shut down through atexit, after the application's handlers, so the bug doesn't occur there and this code path isn't reached.
• fix: ApiClient finalizer during interpreter shutdown #720 also hardened interpreter shutdown, in ApiClient.__del__. This is a different code path.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• pytest tests/test_WriteApiBatching.py completes successfully (30 passed, including the new tests)
• Commit messages are conventional
• Sign CLA (if not already signed)

Tests

BatchingWriteInterpreterShutdownTest in tests/test_WriteApiBatching.py runs the scenario from the issue in a separate interpreter against a local HTTP server:

• test_close_in_atexit: a batch written before exit arrives when the WriteApi is closed in an atexit handler.
• test_write_and_close_in_atexit: a point written inside the atexit handler itself arrives.

Both fail on master with the error from the issue and pass with this change (Python 3.11 and 3.13; reactivex 4.0.4, 5.1.0 and 6.1.0).

pytest tests/test_WriteApiBatching.py -k InterpreterShutdown

AI/LLM disclosure

• AI coding tools (Claude Code) were used to trace the shutdown order, draft the change and the tests, and write this description.
• I reviewed the complete change, understand the reasoning, and ran the reported local tests before submitting.
• AI output was not pasted unreviewed.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.47%. Comparing base (ef60f89) to head (c1f12bf).

Files with missing lines	Patch %	Lines
influxdb_client/client/write_api.py	50.00%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #733      +/-   ##
==========================================
- Coverage   90.49%   90.47%   -0.03%     
==========================================
  Files          40       40              
  Lines        3568     3570       +2     
==========================================
+ Hits         3229     3230       +1     
- Misses        339      340       +1     

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