[Backport 7.77.x] [CWS] Fix panic on closed channel during APIServer shutdown

[dd-octo-sts]

Backport 9ee6410 from #47047.

---

What does this PR do?

Wait for the APIServer.start() goroutine to finish before stopping pipeline providers, preventing a race where events are sent on a closed logChan.

Motivation

During system-probe shutdown, CWSConsumer.Stop() calls c.cancelFnc() to cancel the Go context, and then c.apiServer.Stop(). c.apiServer.Stop() then calls a.stopper.Stop() to close the logChan channel. However, the APIServer.start() goroutine was not tracked by any synchronization primitive, so after the Go context was cancelled the goroutine could still be in the middle of a dequeue cycle while the logChan channel was already closed.

This resulted in the following panic:

panic: send on closed channel
goroutine 781 [running]:
    github.com/DataDog/datadog-agent/pkg/security/reporter.(*RuntimeReporter).ReportRaw(0x4000e84e20, {0x4003c26000, 0x3d43, 0x4000}, {0x0, 0x0}, {0x40009f7b48?, 0x1a15a98?, 0x0?}, {0x400209a880, ...})
    github.com/DataDog/datadog-agent/pkg/security/reporter/reporter.go:39 +0x1d0
    github.com/DataDog/datadog-agent/pkg/security/module.(*DirectEventMsgSender).Send(0x400278a2a0, 0x400295d7c0, 0x3a?)
    github.com/DataDog/datadog-agent/pkg/security/module/msg_sender.go:100 +0x138
    github.com/DataDog/datadog-agent/pkg/security/module.(*APIServer).start.func1(0x40016c3e00, 0x1)
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:386 +0x400
    github.com/DataDog/datadog-agent/pkg/security/module.(*APIServer).dequeue.func1(...)
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:256
    github.com/DataDog/datadog-agent/pkg/security/module.slicesDeleteUntilFalse(...)
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:280
    github.com/DataDog/datadog-agent/pkg/security/module.(*APIServer).dequeue(0x40019afa20, {0x4003e2bf20?, 0x48e7fd6f8e4?, 0x401af60?}, 0x40009f7f30)
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:248 +0x1d8
    github.com/DataDog/datadog-agent/pkg/security/module.(*APIServer).start(0x40019afa20, {0x2ba4608, 0x400225d0e0})
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:337 +0x80
created by github.com/DataDog/datadog-agent/pkg/security/module.(*APIServer).Start in goroutine 1
    github.com/DataDog/datadog-agent/pkg/security/module/server.go:412 +0x1d0

Describe how you validated your changes

Additional Notes

[agent-platform-auto-pr]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 6a99406
📊 Static Quality Gates Dashboard
🔗 SQG Job

31 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	756.410 MiB
✅	agent_deb_amd64_fips	715.088 MiB
✅	agent_heroku_amd64	323.756 MiB
✅	agent_msi	622.544 MiB
✅	agent_rpm_amd64	756.394 MiB
✅	agent_rpm_amd64_fips	715.072 MiB
✅	agent_rpm_arm64	734.517 MiB
✅	agent_rpm_arm64_fips	696.212 MiB
✅	agent_suse_amd64	756.394 MiB
✅	agent_suse_amd64_fips	715.072 MiB
✅	agent_suse_arm64	734.517 MiB
✅	agent_suse_arm64_fips	696.212 MiB
✅	docker_agent_amd64	817.431 MiB
✅	docker_agent_arm64	820.290 MiB
✅	docker_agent_jmx_amd64	1008.343 MiB
✅	docker_agent_jmx_arm64	999.983 MiB
✅	docker_cluster_agent_amd64	203.000 MiB
✅	docker_cluster_agent_arm64	217.455 MiB
✅	docker_cws_instrumentation_amd64	7.135 MiB
✅	docker_cws_instrumentation_arm64	6.689 MiB
✅	docker_dogstatsd_amd64	38.500 MiB
✅	docker_dogstatsd_arm64	36.812 MiB
✅	dogstatsd_deb_amd64	29.724 MiB
✅	dogstatsd_deb_arm64	27.881 MiB
✅	dogstatsd_rpm_amd64	29.724 MiB
✅	dogstatsd_suse_amd64	29.724 MiB
✅	iot_agent_deb_amd64	42.617 MiB
✅	iot_agent_deb_arm64	39.723 MiB
✅	iot_agent_deb_armhf	40.447 MiB
✅	iot_agent_rpm_amd64	42.618 MiB
✅	iot_agent_suse_amd64	42.618 MiB

On-wire sizes (compressed)

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-30.62 KiB (0.02% reduction)	185.674 → 185.644 → 186.090
✅	agent_deb_amd64_fips	+6.27 KiB (0.00% increase)	176.307 → 176.314 → 180.330
✅	agent_heroku_amd64	neutral	87.104 MiB → 88.440
✅	agent_msi	-4.0 KiB (0.00% reduction)	149.379 → 149.375 → 154.470
✅	agent_rpm_amd64	-2.13 KiB (0.00% reduction)	187.575 → 187.572 → 189.170
✅	agent_rpm_amd64_fips	+48.41 KiB (0.03% increase)	178.416 → 178.463 → 181.060
✅	agent_rpm_arm64	+23.45 KiB (0.01% increase)	169.836 → 169.859 → 170.020
✅	agent_rpm_arm64_fips	neutral	162.470 MiB → 164.130
✅	agent_suse_amd64	-2.13 KiB (0.00% reduction)	187.575 → 187.572 → 189.170
✅	agent_suse_amd64_fips	+48.41 KiB (0.03% increase)	178.416 → 178.463 → 181.060
✅	agent_suse_arm64	+23.45 KiB (0.01% increase)	169.836 → 169.859 → 170.020
✅	agent_suse_arm64_fips	neutral	162.470 MiB → 164.130
✅	docker_agent_amd64	neutral	277.932 MiB → 279.410
✅	docker_agent_arm64	neutral	265.209 MiB → 267.960
✅	docker_agent_jmx_amd64	-2.09 KiB (0.00% reduction)	346.589 → 346.587 → 348.040
✅	docker_agent_jmx_arm64	+2.09 KiB (0.00% increase)	329.850 → 329.852 → 332.560
✅	docker_cluster_agent_amd64	neutral	71.131 MiB → 71.920
✅	docker_cluster_agent_arm64	neutral	66.773 MiB → 67.220
✅	docker_cws_instrumentation_amd64	neutral	2.995 MiB → 3.330
✅	docker_cws_instrumentation_arm64	neutral	2.726 MiB → 3.090
✅	docker_dogstatsd_amd64	neutral	14.901 MiB → 15.820
✅	docker_dogstatsd_arm64	neutral	14.237 MiB → 14.830
✅	dogstatsd_deb_amd64	-2.23 KiB (0.03% reduction)	7.856 → 7.853 → 8.790
✅	dogstatsd_deb_arm64	neutral	6.743 MiB → 7.710
✅	dogstatsd_rpm_amd64	neutral	7.867 MiB → 8.800
✅	dogstatsd_suse_amd64	neutral	7.867 MiB → 8.800
✅	iot_agent_deb_amd64	neutral	11.237 MiB → 12.040
✅	iot_agent_deb_arm64	+2.9 KiB (0.03% increase)	9.601 → 9.604 → 10.450
✅	iot_agent_deb_armhf	neutral	9.802 MiB → 10.620
✅	iot_agent_rpm_amd64	neutral	11.256 MiB → 12.060
✅	iot_agent_suse_amd64	neutral	11.256 MiB → 12.060

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 119f05db-ddc2-4853-be5d-8efa69099179

Baseline: 69849fb
Comparison: 62f24b7
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	+0.32	[-2.81, +3.44]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	ddot_metrics_sum_cumulative	memory utilization	+0.73	[+0.58, +0.89]	1	Logs
➖	docker_containers_cpu	% cpu utilization	+0.32	[-2.81, +3.44]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	+0.21	[+0.01, +0.41]	1	Logs
➖	otlp_ingest_metrics	memory utilization	+0.06	[-0.10, +0.22]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+0.04	[+0.00, +0.08]	1	Logs bounds checks dashboard
➖	file_to_blackhole_100ms_latency	egress throughput	+0.02	[-0.02, +0.07]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.02	[-0.47, +0.50]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.11, +0.14]	1	Logs
➖	quality_gate_idle	memory utilization	+0.01	[-0.04, +0.05]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_to_api_v3	ingress throughput	-0.00	[-0.13, +0.13]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.09, +0.08]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.03	[-0.41, +0.36]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.05	[-0.48, +0.38]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.19	[-0.42, +0.04]	1	Logs
➖	ddot_logs	memory utilization	-0.20	[-0.26, -0.14]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.28	[-0.35, -0.22]	1	Logs
➖	docker_containers_memory	memory utilization	-0.29	[-0.36, -0.22]	1	Logs
➖	file_tree	memory utilization	-0.39	[-0.43, -0.34]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.46	[-0.51, -0.40]	1	Logs
➖	otlp_ingest_logs	memory utilization	-0.46	[-0.56, -0.37]	1	Logs
➖	ddot_metrics	memory utilization	-0.52	[-0.74, -0.31]	1	Logs
➖	quality_gate_logs	% cpu utilization	-1.04	[-2.55, +0.48]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-1.21	[-1.41, -1.00]	1	Logs bounds checks dashboard

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_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_metrics_logs, bounds check cpu_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 memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check lost_bytes: 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_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 lost_bytes: 10/10 replicas passed. Gate passed.