fix(forwarder): stop validating MRF alias API keys against US1

[tobz]

What does this PR do?

Updates the forwarder health check logic for validating API keys to properly handle customer-specific Multi-Region Failover (DDR) endpoints such that it doesn't mistakenly transform the URL, instead sending the validation request to the (potentially) wrong datacenter.

Motivation

Customers doing DNS-based failover point dd_url at an MRF alias. The alias sits in the datadoghq.com zone regardless of the underlying datacenters that it may be pointed at, so the faulty logic prior to this PR would cause the health check to always send the API key validation request to datadoghq.com, or US1. For customers that don't actually live on US1, that results in an invalid API key: the forwarder is marked unhealthy and the readiness probe fails, even though payloads are accepted. Even worse, the logic allows this to sometimes work if a customer with their MRF-specific failover configuration has US1 either as their primary or failover region, since API keys are copied to both.

We fixed this by adding a new helper function (APIEndpointFromURL) which properly handles these customer-specific MRF endpoints. In doing so, we've also fixed some other edge cases that the forwarder health check's previous logic didn't handle correctly, like a URL with a port, or non-standard casing, and so on.

Additional Notes

There's still some code that ultimately touches/handles MRF-specific endpoint overrides (via dd_url) in an incorrect way due to doing their own thing:

• pkg/serializer/metrics.go: v3beta shadow sampling for sketches uses ExtractSiteFromURL, and shadow_sites defaults to [datadoghq.com], so alias users get shadow traffic as if they were on US1.
• comp/core/delegatedauth/api/delegated_auth.go: has its own regex that maps the alias to api.datadoghq.com.
• pkg/privateactionrunner/enrollment/enrollment.go: enrolls against api. + ExtractSiteFromURL(dd_url), i.e. US1.

I opted to ignore those for the moment but could just as easily add them here if folks have a strong opinion on doing so.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[github-actions]

AI review by Codex (OpenAI) - workflow run

The patch is correct. The helper preserves customer-specific MRF aliases for validation while routing recognized Datadog sites to their API endpoints. No actionable regressions were identified. Live support for /api/v1/validate on MRF aliases remains unverified.

[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 85.71%
• Overall Coverage: 52.13% (-6.47%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 75e0e6a | Docs | Give us feedback!}

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor d533b7b0:

Results for datadog-agent_7.86.0~devel.git.277.75e0e6a.pipeline.143802315-1_amd64.deb:

No change detected

Results for datadog-iot-agent_7.86.0~devel.git.277.75e0e6a.pipeline.143802315-1_amd64.deb:

No change detected

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor d533b7b
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-2.16 KiB (0.00% reduction, +0.04% of buffer)	755.160 → 755.158 → 760.520
✅	agent_deb_amd64_fips	-2.16 KiB (0.00% reduction, +0.04% of buffer)	688.174 → 688.172 → 693.570
✅	agent_msi	+2.0 KiB (0.00% increase, -0.48% of buffer)	653.779 → 653.781 → 654.190
✅	agent_rpm_amd64	-2.16 KiB (0.00% reduction, +0.04% of buffer)	755.144 → 755.142 → 760.500
✅	agent_rpm_amd64_fips	-2.16 KiB (0.00% reduction, +0.04% of buffer)	688.158 → 688.156 → 693.550
✅	agent_rpm_arm64	+4.35 KiB (0.00% increase, -0.08% of buffer)	725.698 → 725.702 → 731.100
✅	agent_rpm_arm64_fips	+8.0 KiB (0.00% increase, -0.14% of buffer)	664.281 → 664.289 → 669.740
✅	agent_suse_amd64	-2.16 KiB (0.00% reduction, +0.04% of buffer)	755.144 → 755.142 → 760.500
✅	agent_suse_amd64_fips	-2.16 KiB (0.00% reduction, +0.04% of buffer)	688.158 → 688.156 → 693.550
✅	agent_suse_arm64	+4.35 KiB (0.00% increase, -0.08% of buffer)	725.698 → 725.702 → 731.100
✅	agent_suse_arm64_fips	+8.0 KiB (0.00% increase, -0.14% of buffer)	664.281 → 664.289 → 669.740
✅	docker_agent_amd64	-2.17 KiB (0.00% reduction, +0.04% of buffer)	811.331 → 811.329 → 816.720
✅	docker_agent_arm64	+4.35 KiB (0.00% increase, -0.08% of buffer)	806.504 → 806.508 → 811.970
✅	docker_agent_jmx_amd64	-2.16 KiB (0.00% reduction, +0.04% of buffer)	1002.201 → 1002.199 → 1007.590
✅	docker_agent_jmx_arm64	+4.36 KiB (0.00% increase, -0.08% of buffer)	986.153 → 986.158 → 991.620
✅	docker_cluster_agent_arm64	-64.0 KiB (0.03% reduction, +1.96% of buffer)	224.224 → 224.161 → 227.410

17 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_heroku_amd64	319.074 MiB
✅	docker_cws_instrumentation_amd64	7.443 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.543 MiB
✅	docker_dogstatsd_arm64	37.629 MiB
✅	docker_host_profiler_amd64	308.680 MiB
✅	docker_host_profiler_arm64	319.791 MiB
✅	dogstatsd_deb_amd64	30.285 MiB
✅	dogstatsd_deb_arm64	28.274 MiB
✅	dogstatsd_rpm_amd64	30.285 MiB
✅	dogstatsd_suse_amd64	30.285 MiB
✅	iot_agent_deb_amd64	47.371 MiB
✅	iot_agent_deb_arm64	43.837 MiB
✅	iot_agent_deb_armhf	44.648 MiB
✅	iot_agent_rpm_amd64	47.371 MiB
✅	iot_agent_suse_amd64	47.370 MiB
✅	docker_cluster_agent_amd64	211.192 MiB

[github-actions]

AI review by Codex (OpenAI) - workflow run

The patch is correct. MRF aliases remain unchanged during both initial validation and API-key rotation, while recognized Datadog sites resolve to their API endpoints. No actionable regressions found. Tests were not run because dda is unavailable.

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: 4d486dd2-8ad1-44c3-84e1-619cf8dc0c14

Baseline: d533b7b
Comparison: 75e0e6a
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_memory	memory utilization	+1.04	[+0.83, +1.25]	1	Logs
➖	dsd_uds_client_drop_detector_cpu	% cpu utilization	+0.82	[+0.33, +1.31]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+0.19	[+0.11, +0.27]	1	Logs bounds checks dashboard
➖	python_openmetrics	% cpu utilization	+0.12	[-0.56, +0.80]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	+0.04	[+0.01, +0.07]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.02	[-0.20, +0.25]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	-0.06	[-0.13, +0.02]	1	Logs bounds checks dashboard
➖	dsd_uds_10mb_3k_timestamped_contexts_cpu	% cpu utilization	-0.44	[-0.68, -0.21]	1	Logs
➖	quality_gate_idle	memory utilization	-0.46	[-0.49, -0.42]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	-0.49	[-0.53, -0.45]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	-0.76	[-0.89, -0.63]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-0.90	[-1.76, -0.05]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	python_openmetrics	checks_execution_time	10/10	78.57 ≤ 100	bounds checks dashboard
✅	python_openmetrics	cpu_usage	10/10	1334.12 ≤ 1500	bounds checks dashboard
✅	python_openmetrics	memory_usage	10/10	4.31GiB ≤ 4.75GiB	bounds checks dashboard
✅	quality_gate_idle	intake_connections	10/10	4 ≤ 5	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	176.74MiB ≤ 181MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	767.31KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	2 ≤ 5	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	474.53MiB ≤ 542MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.13MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	16 ≤ 40	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	211.58MiB ≤ 228MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.00MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	376.26 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	20 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	421.50MiB ≤ 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	0.95GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_private_action_runner	memory_usage	10/10	73.63MiB ≤ 77MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	29.10 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	328.60MiB ≤ 357MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	69.13 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	303.82MiB ≤ 337MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	23.40 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	314.55MiB ≤ 348MiB	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_mean_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_logs, bounds check missed_bytes: 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 memory_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 memory_usage: 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_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_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_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_security_no_fs_load, 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_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.