Do not merge: add CDK deadlock diagnostics for pinned prerelease

[devin-ai-integration]

Summary

Do not merge. This is a diagnostic-only branch requested by gl_anatolii.yatsuk for the Zendesk Support heartbeat/deadlock investigation in https://github.com/airbytehq/oncall/issues/12725. The intended workflow is to publish/pin a prerelease image from this branch to affected users, collect stderr heartbeat/thread-dump evidence, then discard the branch.

The connector entrypoint now always starts a daemon diagnostic heartbeat in this branch. Every 30s it writes directly to stderr:

STDOUT_HEARTBEAT: t=... msgs=... bytes=... print_blocked=... queue_size=... queue_full=...

If the emitted message count is frozen for 3 heartbeat intervals, it appends a full Python thread dump, then repeats the dump every 10 stalled intervals. This adapts the diagnostic behavior from #1027 for prerelease pinning, where no additional environment variable can be set on the affected connections.

Also registers the concurrent source queue while active so the heartbeat can distinguish likely stdout backpressure/full-queue stalls from other blocked-thread patterns.

Validation:

• poetry run pytest unit_tests/test_entrypoint.py -k 'deadlock_diagnostics or launch_starts_deadlock'
• poetry run pytest unit_tests/test_entrypoint.py
• poetry run ruff check airbyte_cdk/entrypoint.py airbyte_cdk/sources/concurrent_source/concurrent_source.py airbyte_cdk/sources/concurrent_source/queue_registry.py unit_tests/test_entrypoint.py
• poetry run ruff format --check airbyte_cdk/entrypoint.py airbyte_cdk/sources/concurrent_source/concurrent_source.py airbyte_cdk/sources/concurrent_source/queue_registry.py unit_tests/test_entrypoint.py
• poetry run mypy --config-file mypy.ini airbyte_cdk/entrypoint.py airbyte_cdk/sources/concurrent_source/concurrent_source.py airbyte_cdk/sources/concurrent_source/queue_registry.py

Link to Devin session: https://app.devin.ai/sessions/d5860b3efd2d4aaeb00803ff700663b5

[devin-ai-integration]

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[github-actions]

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Testing This CDK Version

You can test this version of the CDK using the following:

# Run the CLI from this branch:
uvx 'git+https://github.com/airbytehq/airbyte-python-cdk.git@devin/1780315213-deadlock-diagnostics#egg=airbyte-python-cdk[dev]' --help

# Update a connector to use the CDK from this branch ref:
cd airbyte-integrations/connectors/source-example
poe use-cdk-branch devin/1780315213-deadlock-diagnostics

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[github-actions]

PyTest Results (Fast)

4 097 tests  +3   4 086 ✅ +3   8m 13s ⏱️ -13s
    1 suites ±0      11 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit ac5d348. ± Comparison against base commit a7b0929.

♻️ This comment has been updated with latest results.

[github-actions]

PyTest Results (Full)

4 100 tests  +3   4 088 ✅ +3   12m 4s ⏱️ +27s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit ac5d348. ± Comparison against base commit a7b0929.

♻️ This comment has been updated with latest results.