fix(cloudfoundry): avoid typed-nil DCAClient in cf_vm workloadmeta collector

[Kyle-Neale]

Summary

• GetClusterAgentClient() returns a concrete *DCAClient on its error path (changed from DCAClientInterface in [CONTP-1679] feat(Autodiscovery): Add Instrumentation check AD provider  #50814). cf_vm.go's getDCAClient assigned that into the interface field c.dcaClient before checking the error, which poisons the field with a non-nil interface wrapping a nil pointer.
• The next Pull() cycle short-circuits past the (now useless) nil check on c.dcaClient and calls GetCFAppsMetadataForNode on the nil *DCAClient receiver, panicking with a nil-pointer dereference.
• On TAS/PCF this crash-loops the node agent whenever the cluster agent is unreachable (e.g. during initial tile install/bump, before the DCA is deployed), which can abort cf apply-changes entirely.
• Fix: only assign to c.dcaClient after confirming err == nil, and have Pull() use the already-guarded local value instead of re-reading the field. Also added a mutex around getDCAClient, since it's reachable from concurrent Pull calls and was previously unlocked.

Considered reverting GetClusterAgentClient()'s return type back to DCAClientInterface instead, but that would break comp/core/autodiscovery/providers/instrumentationchecks.go (added in the same #50814), which needs the assignment to satisfy a different, narrower interface that DCAClientInterface doesn't cover. Fixing the consumer is the safe path.

Test plan

• Added TestPullDCAUnreachableTwice, which reproduces the exact panic (buildURL → doQuery → GetCFAppsMetadataForNode on a nil receiver) on the second Pull() when the cluster agent is unreachable — verified it panics against the old logic and passes against this fix.
• go test -race ./comp/core/workloadmeta/collectors/internal/cloudfoundry/vm/... passes (all 9 tests).
• Audited other callers of GetClusterAgentClient() for the same poison-before-check pattern; only this one was vulnerable.

[datadog-prod-us1-4]

🎯 Code Coverage (details)
• Patch Coverage: 80.00%
• Overall Coverage: 52.39% (+0.01%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 9a8a2b8 | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 3b2688f
📊 Static Quality Gates Dashboard
🔗 SQG Job
SOME SIZE DELTAS ARE N/A (ANCESTOR METRICS NOT YET AVAILABLE). RETRY JOB

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	N/A	N/A → 759.616 → 764.500
✅	agent_deb_amd64_fips	N/A	N/A → 712.477 → 715.740
✅	agent_heroku_amd64	N/A	N/A → 311.955 → 319.050
✅	agent_rpm_amd64	N/A	N/A → 759.600 → 764.470
✅	agent_rpm_amd64_fips	N/A	N/A → 712.460 → 715.740
✅	agent_rpm_arm64	N/A	N/A → 735.359 → 736.540
✅	agent_rpm_arm64_fips	N/A	N/A → 691.546 → 693.690
✅	agent_suse_amd64	N/A	N/A → 759.600 → 764.470
✅	agent_suse_amd64_fips	N/A	N/A → 712.460 → 715.740
✅	agent_suse_arm64	N/A	N/A → 735.359 → 736.540
✅	agent_suse_arm64_fips	N/A	N/A → 691.546 → 693.690
✅	docker_agent_amd64	N/A	N/A → 818.232 → 820.040
✅	docker_agent_arm64	N/A	N/A → 819.035 → 820.740
✅	docker_agent_jmx_amd64	N/A	N/A → 1009.129 → 1010.800
✅	docker_agent_jmx_arm64	N/A	N/A → 998.585 → 1000.420
✅	docker_cluster_agent_amd64	N/A	N/A → 210.475 → 211.300
✅	docker_cluster_agent_arm64	N/A	N/A → 223.456 → 223.810
✅	docker_cws_instrumentation_amd64	N/A	N/A → 7.439 → 7.480
✅	docker_cws_instrumentation_arm64	N/A	N/A → 6.877 → 7.110
✅	docker_dogstatsd_amd64	N/A	N/A → 39.482 → 39.960
✅	docker_dogstatsd_arm64	N/A	N/A → 37.622 → 38.270
✅	docker_host_profiler_amd64	N/A	N/A → 305.814 → 317.690
✅	docker_host_profiler_arm64	N/A	N/A → 317.125 → 328.970
✅	dogstatsd_deb_amd64	N/A	N/A → 30.224 → 31.200
✅	dogstatsd_deb_arm64	N/A	N/A → 28.247 → 29.580
✅	dogstatsd_rpm_amd64	N/A	N/A → 30.224 → 31.200
✅	dogstatsd_suse_amd64	N/A	N/A → 30.224 → 31.200
✅	iot_agent_deb_amd64	N/A	N/A → 46.471 → 47.530
✅	iot_agent_deb_arm64	N/A	N/A → 43.124 → 44.200
✅	iot_agent_deb_armhf	N/A	N/A → 43.907 → 44.990
✅	iot_agent_rpm_amd64	N/A	N/A → 46.472 → 47.530
✅	iot_agent_suse_amd64	N/A	N/A → 46.471 → 47.530

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: fb0f9584-cd3f-4501-b9cb-f96862410eb1

Baseline: 3b2688f
Comparison: 9a8a2b8
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_private_action_runner	memory utilization	+0.67	[+0.55, +0.79]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	+0.19	[+0.04, +0.33]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.17	[-0.08, +0.41]	1	Logs bounds checks dashboard
➖	quality_gate_idle_all_features	memory utilization	+0.14	[+0.10, +0.18]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	+0.03	[-0.09, +0.15]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	+0.03	[-0.05, +0.10]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	-0.22	[-0.33, -0.12]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-0.85	[-1.70, -0.00]	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	171.28MiB ≤ 178MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	742.35KiB ≤ 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	509.60MiB ≤ 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	18 ≤ 40	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	207.77MiB ≤ 229MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	263.78MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	369.87 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	18 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	417.35MiB ≤ 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	72.25MiB ≤ 76MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	27.52 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	326.46MiB ≤ 335MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	62.77 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	300.95MiB ≤ 314MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	21.90 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	313.52MiB ≤ 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_private_action_runner, 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 memory_usage: 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 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_idle_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate 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 total_bytes_received: 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 cpu_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_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_security_idle, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check memory_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 total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.