Prevent deadlocks in the metrics client

[agagniere]

What does this PR do?

Reduce the scope where the metrics client's mutex is held, to prevent a deadlock from happening when the meter's methods want to acquire another mutex

Motivation

Prevent a deadlock we've seen occurring in prod OTAGENT-753

Describe how you validated your changes

Reading the change

Additional Notes

I'm making the assumption that holding the lock is not required when using the meter, just like it is done in the Histogram and Count functions

[songy23]

Is there a simple way to reproduce it in unit tests (e.g with a mock meter)? The change makes sense to me

[agent-platform-auto-pr]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor adfcd28
📊 Static Quality Gates Dashboard

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-81.26 KiB (0.01% reduction)	705.398 → 705.319 → 708.410
✅	agent_deb_amd64_fips	-81.26 KiB (0.01% reduction)	700.680 → 700.600 → 704.000
✅	agent_heroku_amd64	-80.78 KiB (0.02% reduction)	326.998 → 326.919 → 329.530
✅	agent_msi	-77.01 KiB (0.01% reduction)	571.530 → 571.454 → 982.080
✅	agent_rpm_amd64	-81.26 KiB (0.01% reduction)	705.385 → 705.305 → 708.380
✅	agent_rpm_amd64_fips	-81.26 KiB (0.01% reduction)	700.666 → 700.587 → 703.990
✅	agent_rpm_arm64	-81.12 KiB (0.01% reduction)	686.969 → 686.890 → 693.520
✅	agent_rpm_arm64_fips	-81.12 KiB (0.01% reduction)	683.051 → 682.972 → 688.480
✅	agent_suse_amd64	-81.26 KiB (0.01% reduction)	705.385 → 705.305 → 708.380
✅	agent_suse_amd64_fips	-81.26 KiB (0.01% reduction)	700.666 → 700.587 → 703.990
✅	agent_suse_arm64	-81.12 KiB (0.01% reduction)	686.969 → 686.890 → 693.520
✅	agent_suse_arm64_fips	-81.12 KiB (0.01% reduction)	683.051 → 682.972 → 688.480
✅	docker_agent_amd64	-79.47 KiB (0.01% reduction)	767.611 → 767.534 → 770.720
✅	docker_agent_arm64	-79.32 KiB (0.01% reduction)	773.755 → 773.677 → 780.200
✅	docker_agent_jmx_amd64	-79.45 KiB (0.01% reduction)	958.490 → 958.412 → 961.600
✅	docker_agent_jmx_arm64	-79.32 KiB (0.01% reduction)	953.352 → 953.275 → 959.800

15 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	docker_cluster_agent_amd64	180.790 MiB
✅	docker_cluster_agent_arm64	196.620 MiB
✅	docker_cws_instrumentation_amd64	7.135 MiB
✅	docker_cws_instrumentation_arm64	6.689 MiB
✅	docker_dogstatsd_amd64	38.808 MiB
✅	docker_dogstatsd_arm64	37.128 MiB
✅	dogstatsd_deb_amd64	30.031 MiB
✅	dogstatsd_deb_arm64	28.176 MiB
✅	dogstatsd_rpm_amd64	30.031 MiB
✅	dogstatsd_suse_amd64	30.031 MiB
✅	iot_agent_deb_amd64	43.037 MiB
✅	iot_agent_deb_arm64	40.155 MiB
✅	iot_agent_deb_armhf	40.736 MiB
✅	iot_agent_rpm_amd64	43.038 MiB
✅	iot_agent_suse_amd64	43.038 MiB

On-wire sizes (compressed)

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-28.07 KiB (0.02% reduction)	173.358 → 173.330 → 174.490
✅	agent_deb_amd64_fips	-12.34 KiB (0.01% reduction)	172.299 → 172.286 → 173.750
✅	agent_heroku_amd64	-9.79 KiB (0.01% reduction)	87.128 → 87.119 → 88.450
✅	agent_msi	-64.0 KiB (0.04% reduction)	142.965 → 142.902 → 143.020
✅	agent_rpm_amd64	-9.57 KiB (0.01% reduction)	176.103 → 176.094 → 177.660
✅	agent_rpm_amd64_fips	-36.46 KiB (0.02% reduction)	175.043 → 175.007 → 176.600
✅	agent_rpm_arm64	+65.22 KiB (0.04% increase)	159.393 → 159.457 → 161.260
✅	agent_rpm_arm64_fips	-32.72 KiB (0.02% reduction)	158.801 → 158.769 → 160.550
✅	agent_suse_amd64	-9.57 KiB (0.01% reduction)	176.103 → 176.094 → 177.660
✅	agent_suse_amd64_fips	-36.46 KiB (0.02% reduction)	175.043 → 175.007 → 176.600
✅	agent_suse_arm64	+65.22 KiB (0.04% increase)	159.393 → 159.457 → 161.260
✅	agent_suse_arm64_fips	-32.72 KiB (0.02% reduction)	158.801 → 158.769 → 160.550
✅	docker_agent_amd64	-26.65 KiB (0.01% reduction)	261.102 → 261.076 → 262.450
✅	docker_agent_arm64	-3.27 KiB (0.00% reduction)	250.106 → 250.103 → 252.630
✅	docker_agent_jmx_amd64	-8.01 KiB (0.00% reduction)	329.732 → 329.724 → 331.080
✅	docker_agent_jmx_arm64	-11.78 KiB (0.00% reduction)	314.729 → 314.717 → 317.270
✅	docker_cluster_agent_amd64	-3.47 KiB (0.01% reduction)	63.877 → 63.874 → 64.490
✅	docker_cluster_agent_arm64	+9.08 KiB (0.01% increase)	60.160 → 60.169 → 61.170
✅	docker_cws_instrumentation_amd64	neutral	2.994 MiB
✅	docker_cws_instrumentation_arm64	neutral	2.726 MiB
✅	docker_dogstatsd_amd64	neutral	15.026 MiB
✅	docker_dogstatsd_arm64	neutral	14.351 MiB
✅	dogstatsd_deb_amd64	neutral	7.944 MiB
✅	dogstatsd_deb_arm64	neutral	6.825 MiB
✅	dogstatsd_rpm_amd64	neutral	7.956 MiB
✅	dogstatsd_suse_amd64	neutral	7.956 MiB
✅	iot_agent_deb_amd64	neutral	11.275 MiB
✅	iot_agent_deb_arm64	neutral	9.641 MiB
✅	iot_agent_deb_armhf	-2.43 KiB (0.02% reduction)	9.836 → 9.833 → 10.620
✅	iot_agent_rpm_amd64	neutral	11.294 MiB
✅	iot_agent_suse_amd64	neutral	11.294 MiB

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 7f4bdc67-42d2-49c4-99fb-f77d1e97414a

Baseline: adfcd28
Comparison: bbc7914
Diff

Optimization Goals: ✅ No significant changes detected

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	docker_containers_cpu	% cpu utilization	+2.19	[-0.85, +5.23]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_logs	% cpu utilization	+2.59	[+1.12, +4.06]	1	Logs bounds checks dashboard
➖	docker_containers_cpu	% cpu utilization	+2.19	[-0.85, +5.23]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	+1.20	[+0.99, +1.40]	1	Logs bounds checks dashboard
➖	otlp_ingest_metrics	memory utilization	+0.51	[+0.36, +0.66]	1	Logs
➖	ddot_logs	memory utilization	+0.24	[+0.18, +0.29]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.04	[-0.35, +0.44]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.04	[-0.34, +0.41]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	+0.03	[-0.20, +0.26]	1	Logs
➖	quality_gate_idle	memory utilization	+0.02	[-0.02, +0.07]	1	Logs bounds checks dashboard
➖	otlp_ingest_logs	memory utilization	+0.01	[-0.08, +0.10]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.11, +0.13]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.08, +0.09]	1	Logs
➖	docker_containers_memory	memory utilization	-0.00	[-0.08, +0.07]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	-0.00	[-0.14, +0.13]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.03	[-0.07, +0.01]	1	Logs bounds checks dashboard
➖	ddot_metrics_sum_delta	memory utilization	-0.04	[-0.25, +0.17]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.05	[-0.45, +0.35]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.10	[-0.14, -0.05]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.17	[-0.22, -0.11]	1	Logs
➖	file_tree	memory utilization	-0.18	[-0.24, -0.12]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.35	[-0.51, -0.18]	1	Logs
➖	ddot_metrics	memory utilization	-0.42	[-0.64, -0.21]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.58	[-0.66, -0.50]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	docker_containers_cpu	simple_check_run	10/10
✅	docker_containers_memory	memory_usage	10/10
✅	docker_containers_memory	simple_check_run	10/10
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	lost_bytes	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	bounds checks dashboard

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_metrics_logs, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.

[songy23]

Please add a changelog

[drichards-87]

Left some feedback on the release notes from Docs and approved the PR.

[agagniere]

Note : I verified that the test fails on main, and succeeds with the associated changes.

Pushed with --no-verify to allow review of the test, but it is not compatible with go 1.24, unless we activate the GOEXPERIMENT=synctest

[agagniere]

/merge -m squash

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-01-13 13:11:40 UTC ℹ️ Start processing command /merge -m squash

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2026-01-13 13:11:47 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 60m (p90).

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2026-01-13 13:41:50 UTC ℹ️ MergeQueue: This merge request was merged