configstream: add a ConfigUnset event so layer removals cross the wire

[rahulkaukuntla]

What does this PR do?

Adds a ConfigUnset event to the config stream protocol so that clearing a source layer on the core agent is reproduced on subscribers, and fixes Set to notify receivers with the resolved value rather than the one written.

Motivation

Snapshots only carry the core agent's merged view — one entry per key, tagged with the winning source — so a subscriber has no lower layer of its own to fall back to when a layer is cleared. A ConfigUpdate cannot express a removal: it wrote the shadowed value back into the layer being emptied, leaving the subscriber diverged. Reporting the resolved source instead wouldn't help, since the subscriber's stale higher-priority entry would keep winning the merge. So the removal has to cross the wire, and it has to carry what the key resolves to without the cleared layer.

The second commit fixes a related bug on the producer side: Set compared previousValue against its own newValue argument, so a write to a layer that loses the merge notified receivers with a value Get never returns, under the layer written to rather than the one it resolves from. It now reads back from the merged tree.

Describe how you validated your changes

New unit tests in pkg/config/nodetreemodel, producer tests in comp/core/configstream/impl, and a consumer integration test covering the env-var-shadowed-by-agent-runtime case. Both fixes were verified to fail against the unpatched code. Also, live-tested end to end with the real agent and trace-agent binaries streaming over gRPC.

[github-actions]

AI review by Codex (OpenAI) - workflow run

Patch is incorrect: a failed fallback-value encoding is converted into a valid-looking removal event, causing subscribers to permanently diverge.

[rahulkaukuntla]

/dd-review

[github-actions]

AI review by Codex (OpenAI) - workflow run

Verdict

Patch is incorrect. The new event is sent without backward-compatible negotiation, so mixed-version deployments can break config streaming. The protocol documentation is also stale.

[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 73.83%
• Overall Coverage: 52.73% (+0.00%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 7d3ffec | Docs | View more details | Give us feedback!}

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor ac3e2c30:

Results for datadog-agent_7.84.0~devel.git.585.7d3ffec.pipeline.134020131-1_amd64.deb:

No change detected

Results for datadog-iot-agent_7.84.0~devel.git.585.7d3ffec.pipeline.134020131-1_amd64.deb:

No change detected

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor ac3e2c3
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	+48.0 KiB (0.01% increase, -1.50% of buffer)	761.710 → 761.757 → 764.840
✅	agent_deb_amd64_fips	+32.0 KiB (0.00% increase, -1.48% of buffer)	713.971 → 714.002 → 716.080
✅	agent_heroku_amd64	+12.0 KiB (0.00% increase, -0.19% of buffer)	312.986 → 312.998 → 319.080
✅	agent_msi	+52.0 KiB (0.01% increase, -0.40% of buffer)	648.380 → 648.430 → 661.050
✅	agent_rpm_amd64	+48.0 KiB (0.01% increase, -1.50% of buffer)	761.694 → 761.740 → 764.810
✅	agent_rpm_amd64_fips	+32.0 KiB (0.00% increase, -1.47% of buffer)	713.955 → 713.986 → 716.080
✅	agent_rpm_arm64	+44.0 KiB (0.01% increase, -5.91% of buffer)	737.583 → 737.626 → 738.310
✅	agent_rpm_arm64_fips	+32.0 KiB (0.00% increase, -2.67% of buffer)	693.182 → 693.213 → 694.350
✅	agent_suse_amd64	+48.0 KiB (0.01% increase, -1.50% of buffer)	761.694 → 761.740 → 764.810
✅	agent_suse_amd64_fips	+32.0 KiB (0.00% increase, -1.47% of buffer)	713.955 → 713.986 → 716.080
✅	agent_suse_arm64	+44.0 KiB (0.01% increase, -5.91% of buffer)	737.583 → 737.626 → 738.310
✅	agent_suse_arm64_fips	+32.0 KiB (0.00% increase, -2.67% of buffer)	693.182 → 693.213 → 694.350
✅	docker_agent_amd64	+40.0 KiB (0.00% increase, -14.25% of buffer)	820.726 → 820.765 → 821.000
✅	docker_agent_arm64	+43.99 KiB (0.01% increase, -13.08% of buffer)	821.652 → 821.694 → 821.980
✅	docker_agent_jmx_amd64	+40.0 KiB (0.00% increase, -14.38% of buffer)	1011.638 → 1011.677 → 1011.910
✅	docker_agent_jmx_arm64	+44.0 KiB (0.00% increase, -12.78% of buffer)	1001.344 → 1001.387 → 1001.680
✅	docker_cluster_agent_amd64	+4.01 KiB (0.00% increase, -0.45% of buffer)	211.261 → 211.265 → 212.130
✅	docker_host_profiler_amd64	+6.76 KiB (0.00% increase, -0.06% of buffer)	306.872 → 306.878 → 317.700
✅	docker_host_profiler_arm64	+3.46 KiB (0.00% increase, -0.03% of buffer)	318.168 → 318.172 → 328.970
✅	dogstatsd_deb_amd64	+8.0 KiB (0.03% increase, -0.85% of buffer)	30.290 → 30.298 → 31.210
✅	dogstatsd_deb_arm64	+4.0 KiB (0.01% increase, -0.30% of buffer)	28.302 → 28.306 → 29.590
✅	dogstatsd_rpm_amd64	+8.0 KiB (0.03% increase, -0.85% of buffer)	30.290 → 30.298 → 31.210
✅	dogstatsd_suse_amd64	+8.0 KiB (0.03% increase, -0.85% of buffer)	30.290 → 30.298 → 31.210
✅	iot_agent_deb_amd64	+12.0 KiB (0.03% increase, -1.19% of buffer)	46.568 → 46.579 → 47.550
✅	iot_agent_deb_arm64	+8.0 KiB (0.02% increase, -0.77% of buffer)	43.208 → 43.216 → 44.220
✅	iot_agent_deb_armhf	+12.02 KiB (0.03% increase, -1.17% of buffer)	44.015 → 44.026 → 45.020
✅	iot_agent_rpm_amd64	+12.0 KiB (0.03% increase, -1.19% of buffer)	46.568 → 46.580 → 47.550
✅	iot_agent_suse_amd64	+12.0 KiB (0.03% increase, -1.19% of buffer)	46.567 → 46.579 → 47.550

5 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	docker_cluster_agent_arm64	224.398 MiB
✅	docker_cws_instrumentation_amd64	7.439 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.553 MiB
✅	docker_dogstatsd_arm64	37.623 MiB

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: 24b7382c-a539-4bbb-a573-25a9309b233b

Baseline: ac3e2c3
Comparison: 7d3ffec
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	dsd_uds_10mb_3k_timestamped_contexts_cpu	% cpu utilization	+0.84	[+0.58, +1.10]	1	Logs
➖	quality_gate_security_idle	memory utilization	+0.21	[+0.16, +0.26]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	+0.06	[+0.02, +0.09]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	-0.04	[-0.08, +0.01]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-0.06	[-0.29, +0.17]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	-0.27	[-0.34, -0.19]	1	Logs bounds checks dashboard
➖	dsd_uds_10mb_3k_timestamped_contexts_memory	memory utilization	-0.28	[-0.49, -0.06]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.38	[-0.42, -0.34]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	-0.88	[-1.00, -0.75]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-4.21	[-5.07, -3.35]	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	173.41MiB ≤ 179MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	749.04KiB ≤ 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	518.33MiB ≤ 537MiB	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	211.58MiB ≤ 220MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	263.09MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	378.27 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	19 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	438.49MiB ≤ 455MiB	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	71.60MiB ≤ 75MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	29.96 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	326.53MiB ≤ 355MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	61.28 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	307.20MiB ≤ 335MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	23.50 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	314.04MiB ≤ 345MiB	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_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_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_logs, bounds check intake_connections: 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_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, 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 missed_bytes: 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 intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 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 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_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_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.

[github-actions]

AI review by Codex (OpenAI) - workflow run

patch is correct — the unset protocol, producer sequencing, consumer application, and coverage are consistent, with no actionable defects found.