[Enhancement] Implement metrics reporting for `MemTrackerManager` #68170

arin-mirza · 2026-01-20T11:06:06Z

Why I'm doing:

There are currently no backend metrics reporting for memory pools.

I previously tried to add them by extending the workgroup metrics, but this turned out to be an incorrect approach:

[Enhancement] Add mem_pool_use_ratio metric to be #67701

What I'm doing:

This PR implements metric reporting for MemTrackerManager and adds the following new metrics:

mem_pool_mem_limit_bytes
mem_pool_mem_usage_bytes
mem_pool_mem_usage_ratio
mem_pool_workgroup_count

The implementation follows the same locking structure that is present in WorkGroupManager.

It was necessary to add a new mutex for MemTrackerManager because the update_metrics callback hook passed to MetricRegistry needs to be a closure which captures a write lock.
The unlocked gap inside add_metrics method is unavoidable to AB-BA deadlock scenario with the metrics collector.
Metrics entries are never deleted as it would complicate the thread synchronization even further. This is also the case for the existing implementation in WorkGroupManager.

Minor: Changed list_mem_trackers() method to not return the default memory pool name.

Tests and Docs

I did not add any test cases as there were not any for workgroup metrics either. Let me know if this is necessary.
I did not verify that the new metrics are being reported correctly by building and running the starrocks fe/be, as I am currently unable to build the engine locally.
I updated the user documentation.
- I am not a Chinese or Japanese speaker so I used AI for the translation. I would appreciate it if a native speaker could review my additions to ensure the tone is correct. :)

What type of PR is this:

Does this PR entail a change in behavior?

Yes, this PR will result in a change in behavior.
No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

Interface/UI changes: syntax, type conversion, expression evaluation, display information
Parameter changes: default values, similar parameters but with different default values
Policy changes: use new policy to replace old one, functionality automatically enabled
Feature removed
Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

I have added test cases for my bug fix or my new feature
This pr needs user documentation (for new or modified features or behaviors)
- I have added documentation for my new feature or new function
- This pr needs auto generate documentation
This is a backport pr

Bugfix cherry-pick branch check:

Signed-off-by: arin-mirza <[email protected]>

StarRocks-Reviewer · 2026-01-20T11:09:47Z

@cursor review

Signed-off-by: arin-mirza <[email protected]>

…-manager

StarRocks-Reviewer · 2026-01-20T16:07:27Z

@cursor review

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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cursor · 2026-01-20T16:19:24Z

be/src/exec/workgroup/mem_tracker_manager.cpp

+            metrics->mem_limit->set_value(0);
+            metrics->mem_usage_bytes->set_value(0);
+            metrics->mem_usage_ratio->set_value(0);
+            metrics->workgroup_count->set_value(0);


Race condition causes null pointer dereference in metrics update

High Severity

A race condition exists where _update_metrics_unlocked can dereference nullptr metric pointers. When two threads concurrently call _add_metrics_unlocked for the same mem_pool, both pass the contains check at line 87 before either adds an entry. If the thread that failed to register metrics (registry returns false) acquires the lock first at line 115, it creates a MemTrackerMetrics entry with all nullptr members but doesn't move any metrics in. If the metrics collector runs before the successful thread moves its metrics, it will crash dereferencing nullptr at lines 155-164.

Additional Locations (1)

be/src/exec/workgroup/mem_tracker_manager.cpp#L116-L138

Good catch, I thought the update method was protected against this scenario but it's not.

Since any thread which successfully registered at least one metric must run to completion (otherwise some metrics might never get initialized) we cannot solve this inside _add_metrics_unlocked.

I added if guards to _update_metrics_unlocked, which prevents any nullptr dereference. Since all metrics are registered and initialized by some thread, we eventually have a complete metrics object.

Fixed in f7a13d9

The same issue exists in the update method of WorkGroupManager so it should be fixed there too.

Signed-off-by: arin-mirza <[email protected]>

github-actions · 2026-01-20T20:18:03Z

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

github-actions · 2026-01-20T20:18:08Z

[FE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

github-actions · 2026-01-20T20:36:32Z

[BE Incremental Coverage Report]

✅ pass : 57 / 68 (83.82%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	be/src/exec/workgroup/mem_tracker_manager.cpp	55	66	83.33%	[120, 150, 154, 155, 156, 158, 159, 161, 162, 164, 165]
🔵	be/src/exec/workgroup/mem_tracker_manager.h	2	2	100.00%	[]

arin-mirza added 2 commits January 20, 2026 09:59

Implement metrics reporting for MemTrackerManager

42c06fb

Signed-off-by: arin-mirza <[email protected]>

Update documentation

ea66efe

Signed-off-by: arin-mirza <[email protected]>

arin-mirza requested a review from a team as a code owner January 20, 2026 11:06

github-actions bot added behavior_changed documentation Improvements or additions to documentation labels Jan 20, 2026

mergify bot assigned arin-mirza Jan 20, 2026

arin-mirza mentioned this pull request Jan 20, 2026

[Enhancement] Add mem_pool_use_ratio metric to be #67701

Closed

25 tasks

github-actions bot added 4.1 and removed behavior_changed labels Jan 20, 2026

arin-mirza and others added 2 commits January 20, 2026 13:12

Update documentation (Chinese)

677dbea

Signed-off-by: arin-mirza <[email protected]>

Merge branch 'StarRocks:main' into add-metric-registry-to-mem-tracker…

31f8965

…-manager

cursor bot reviewed Jan 20, 2026

View reviewed changes

Prevent nullptr dereference in update metrics method

f7a13d9

Signed-off-by: arin-mirza <[email protected]>

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[Enhancement] Implement metrics reporting for `MemTrackerManager` #68170

[Enhancement] Implement metrics reporting for `MemTrackerManager` #68170

arin-mirza commented Jan 20, 2026 •

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arin-mirza commented Jan 20, 2026 • edited by github-actions bot Loading Uh oh! There was an error while loading. Please reload this page.

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Why I'm doing:

What I'm doing:

Tests and Docs

What type of PR is this:

Checklist:

Bugfix cherry-pick branch check:

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Race condition causes null pointer dereference in metrics update

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[Java-Extensions Incremental Coverage Report]

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[FE Incremental Coverage Report]

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[BE Incremental Coverage Report]

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[Enhancement] Implement metrics reporting for `MemTrackerManager` #68170

[Enhancement] Implement metrics reporting for `MemTrackerManager` #68170

arin-mirza commented Jan 20, 2026 •

edited by github-actions bot

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