Expose cgroup v2 memory.events as Prometheus metrics

[sohankunkerkar]

Kubernetes KEP-2570 (MemoryQoS) uses cgroup v2 memory.high for throttling and memory.min/memory.low for memory protection. To observe the effect of these settings, operators need visibility into memory pressure events. cadvisor currently does not read the memory.events cgroup file. The existing container_oom_events_total metric comes from kernel log parsing, not cgroup counters.

Read memory.events on cgroup v2 and expose two new Prometheus counter metrics:

• container_memory_events_high_total: times the container was throttled for breaching memory.high
• container_memory_events_max_total: times the container's usage hit memory.max

xref: kubernetes/enhancements#2570

[sohankunkerkar]

cc @haircommander

[sohankunkerkar]

@dims could you take a look at it?

[dims]

@sohankunkerkar no tests at all? :(

• add a unit test in container/libcontainer/handler_test.go?
• integration/tests/metrics/prometheus_test.go::TestCoreMemoryMetricsExist (add to memoryMetrics array)
• integration/tests/api/event_test.go::TestOomKillEventConstraint (same setup as the OOM test, but poll /metrics until container_memory_events_max_total{name~containerID} > 0.)

[sohankunkerkar]

@sohankunkerkar no tests at all? :(

• add a unit test in container/libcontainer/handler_test.go?
• integration/tests/metrics/prometheus_test.go::TestCoreMemoryMetricsExist (add to memoryMetrics array)
• integration/tests/api/event_test.go::TestOomKillEventConstraint (same setup as the OOM test, but poll /metrics until container_memory_events_max_total{name~containerID} > 0.)

@dims I addressed your comments. Could you take a look at it again? Thanks!

[dims]

@sohankunkerkar https://github.com/google/cadvisor/actions/runs/25805017191/job/75842992013?pr=3870

[dims]

thanks @sohankunkerkar

[sohankunkerkar]

@dims Thanks for reviewing this PR. I had one quick question: do we have any plans to cut a new release of cAdvisor anytime soon? We might need it for testing the MemoryQoS feature in Kubernetes.

[dims]

@sohankunkerkar i try to do at least one release of cadvisor to support k8s. Will take stock soon-ish. Do you need this in short order? (weeks? days?)

[sohankunkerkar]

@sohankunkerkar i try to do at least one release of cadvisor to support k8s. Will take stock soon-ish. Do you need this in short order? (weeks? days?)

Thanks for the update! It would be ideal if we could get that once the v1.37 branch opens, or before the feature freeze maybe?