fix(otelcol/metricsclient): fix data race on StatsdClientWrapper.delegate

[pgimalac]

What does this PR do?

Fixes a data race on StatsdClientWrapper.delegate: SetDelegate correctly locked m.mutex, but all delegation methods (Gauge, Count, Histogram, Incr, etc.) read m.delegate without the lock, racing with SetDelegate during otelcol collector startup. Switched mutex to sync.RWMutex and added RLock/RUnlock + local snapshot in every delegation method.

Motivation

Fix a race, found via a race-detector-enabled build in staging (see #54333 for context).

Describe how you validated your changes

Added TestStatsdClientWrapperConcurrentSetDelegateAndCount which races SetDelegate against concurrent Count calls; it reproduces the race under -race before the fix and is clean after (dda inv test --targets=./comp/otelcol/otlp/components/metricsclient/... --race).

[github-actions]

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[chatgpt-codex-connector]

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[datadog-datadog-us1-prod]

🎯 Code Coverage (details)
• Patch Coverage: 18.18%
• Overall Coverage: 52.40% (+0.05%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 3e06840 | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor 235b2902:

Results for datadog-agent_7.84.0~devel.git.207.3e06840.pipeline.131058505-1_amd64.deb:

No change detected

Results for datadog-iot-agent_7.84.0~devel.git.207.3e06840.pipeline.131058505-1_amd64.deb:

No change detected

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 235b290
📊 Static Quality Gates Dashboard
🔗 SQG Job

32 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	759.617 MiB
✅	agent_deb_amd64_fips	712.473 MiB
✅	agent_heroku_amd64	311.955 MiB
✅	agent_rpm_amd64	759.600 MiB
✅	agent_rpm_amd64_fips	712.457 MiB
✅	agent_rpm_arm64	735.360 MiB
✅	agent_rpm_arm64_fips	691.546 MiB
✅	agent_suse_amd64	759.600 MiB
✅	agent_suse_amd64_fips	712.457 MiB
✅	agent_suse_arm64	735.360 MiB
✅	agent_suse_arm64_fips	691.546 MiB
✅	docker_agent_amd64	818.232 MiB
✅	docker_agent_arm64	819.035 MiB
✅	docker_agent_jmx_amd64	1009.130 MiB
✅	docker_agent_jmx_arm64	998.585 MiB
✅	docker_cluster_agent_amd64	210.475 MiB
✅	docker_cluster_agent_arm64	223.456 MiB
✅	docker_cws_instrumentation_amd64	7.439 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.482 MiB
✅	docker_dogstatsd_arm64	37.560 MiB
✅	docker_host_profiler_amd64	305.814 MiB
✅	docker_host_profiler_arm64	317.125 MiB
✅	dogstatsd_deb_amd64	30.224 MiB
✅	dogstatsd_deb_arm64	28.247 MiB
✅	dogstatsd_rpm_amd64	30.224 MiB
✅	dogstatsd_suse_amd64	30.224 MiB
✅	iot_agent_deb_amd64	46.467 MiB
✅	iot_agent_deb_arm64	43.124 MiB
✅	iot_agent_deb_armhf	43.907 MiB
✅	iot_agent_rpm_amd64	46.468 MiB
✅	iot_agent_suse_amd64	46.467 MiB

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: 57bc354e-a24c-4eb9-84b4-60fe9a6f5757

Baseline: 235b290
Comparison: 3e06840
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_idle_all_features	memory utilization	+0.51	[+0.47, +0.55]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	+0.31	[+0.16, +0.46]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	+0.03	[-0.09, +0.15]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	+0.03	[-0.09, +0.15]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.03	[-0.21, +0.27]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	-0.17	[-0.25, -0.10]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	-0.21	[-0.31, -0.11]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-1.57	[-2.44, -0.69]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	quality_gate_idle	intake_connections	10/10	4 = 4	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	174.66MiB ≤ 178MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	744.37KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	4 = 4	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	520.08MiB ≤ 538MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.14MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	15 ≤ 40	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	202.32MiB ≤ 229MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.18MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	357.15 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	16 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	398.29MiB ≤ 439MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	total_bytes_received	10/10	0.94GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_private_action_runner	memory_usage	10/10	72.09MiB ≤ 76MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	27.33 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	323.23MiB ≤ 335MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	59.33 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	303.54MiB ≤ 314MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	22.49 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	311.57MiB ≤ 343MiB	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 missed_bytes: 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 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 total_bytes_received: 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.
• quality_gate_idle, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, 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 missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_security_mean_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_mean_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.