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Posted to commits@airflow.apache.org by "kaxil (via GitHub)" <gi...@apache.org> on 2025/05/23 23:43:03 UTC
[PR] Prevent CPU spike in task supervisor when heartbeat timeout exceeded [airflow]
kaxil opened a new pull request, #51023:
URL: https://github.com/apache/airflow/pull/51023
closes https://github.com/apache/airflow/issues/50507
When the task supervisor's heartbeat timeout is exceeded, the `max_wait_time` calculation can become 0 or negative, causing `selector.select(timeout=0)` to run in a tight non-blocking loop that consumes 100% CPU as explained in the GitHub issue.
Add minimum timeout of 0.01s in `_service_subprocess` to prevent this issue while maintaining responsive task monitoring.
**Root Cause:**
The issue occurs in the `_monitor_subprocess` method when:
1. `last_heartbeat_ago` becomes very large e.g., 100+ seconds due to bugs like network issues or due to bugs like https://github.com/apache/airflow/issues/50500
2. The calculation `HEARTBEAT_TIMEOUT - last_heartbeat_ago * 0.75` becomes negative
3. `max(0, negative_value)` results in 0
4. `selector.select(timeout=0)` runs in a non-blocking tight loop
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Re: [PR] Prevent CPU spike in task supervisor when heartbeat timeout exceeded [airflow]
Posted by "kaxil (via GitHub)" <gi...@apache.org>.
kaxil merged PR #51023:
URL: https://github.com/apache/airflow/pull/51023
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Re: [PR] Prevent CPU spike in task supervisor when heartbeat timeout exceeded [airflow]
Posted by "kaxil (via GitHub)" <gi...@apache.org>.
kaxil commented on code in PR #51023:
URL: https://github.com/apache/airflow/pull/51023#discussion_r2105763025
##########
task-sdk/src/airflow/sdk/execution_time/supervisor.py:
##########
@@ -685,7 +685,9 @@ def _service_subprocess(
:param expect_signal: Signal not to log if the task exits with this code.
:returns: The process exit code, or None if it's still alive
"""
- events = self.selector.select(timeout=max_wait_time)
+ # Ensure minimum timeout to prevent CPU spike with tight loop when timeout is 0 or negative
+ timeout = max(0.01, max_wait_time)
+ events = self.selector.select(timeout=timeout)
Review Comment:
This change could have been in `_monitor_subprocess(` but `_service_subprocess` is called from 2 places: 1) `_monitor_subprocess(` and `kill` ( [code](https://github.com/apache/airflow/blob/65fac1a9fa5fee59ff88aaddcd7a6154bd348dd8/task-sdk/src/airflow/sdk/execution_time/supervisor.py#L596) ) -- so I did it here
https://github.com/apache/airflow/blob/65fac1a9fa5fee59ff88aaddcd7a6154bd348dd8/task-sdk/src/airflow/sdk/execution_time/supervisor.py#L876C9-L895
##########
task-sdk/src/airflow/sdk/execution_time/supervisor.py:
##########
@@ -685,7 +685,9 @@ def _service_subprocess(
:param expect_signal: Signal not to log if the task exits with this code.
:returns: The process exit code, or None if it's still alive
"""
- events = self.selector.select(timeout=max_wait_time)
+ # Ensure minimum timeout to prevent CPU spike with tight loop when timeout is 0 or negative
+ timeout = max(0.01, max_wait_time)
+ events = self.selector.select(timeout=timeout)
Review Comment:
This change could have been in `_monitor_subprocess(` but `_service_subprocess` is called from 2 places: 1) `_monitor_subprocess(` and `kill` ( [code](https://github.com/apache/airflow/blob/65fac1a9fa5fee59ff88aaddcd7a6154bd348dd8/task-sdk/src/airflow/sdk/execution_time/supervisor.py#L596) ) -- so I did it here
https://github.com/apache/airflow/blob/65fac1a9fa5fee59ff88aaddcd7a6154bd348dd8/task-sdk/src/airflow/sdk/execution_time/supervisor.py#L876-L895
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Re: [PR] Prevent CPU spike in task supervisor when heartbeat timeout exceeded [airflow]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #51023:
URL: https://github.com/apache/airflow/pull/51023#issuecomment-2907760505
### Backport successfully created: v3-0-test
<table>
<tr>
<th>Status</th>
<th>Branch</th>
<th>Result</th>
</tr>
<tr>
<td>✅</td>
<td>v3-0-test</td>
<td><a href="https://github.com/apache/airflow/pull/51047"><img src="https://img.shields.io/badge/PR-51047-blue" alt="PR Link"></a></td>
</tr>
</table>
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