[CONTP-849] Fix loop detection bug and add unit tests for cluster agent leader election by zhuminyi · Pull Request #43680 · DataDog/datadog-agent

zhuminyi · 2025-12-01T15:41:35Z

What does this PR do?

Add unit tests for cluster agent leader election and leadership transitions
Fix bug in LeaderForwarder.Forward() where loop detection didn't return after writing error

Motivation

Fixed a bug in pkg/clusteragent/api/leader_forwarder.go where loop detection (via X-DCA-Follower-Forwarded header) wrote an HTTP 508 error but continued to forward the request to the leader anyway.
Added missing return statement to properly short-circuit the request.

New Tests
pkg/clusteragent/api/leader_forwarder_test.go

TestLeaderForwarder_SetLeaderIP - tests leader IP setting, updating, and clearing
TestLeaderForwarder_Forward_NilProxy - tests behavior when no leader is configured
TestLeaderForwarder_Forward_LoopDetection - tests that forwarding loops are properly detected and rejected
TestLeaderForwarder_Forward_WithLeader - tests successful forwarding to leader

pkg/clusteragent/api/leader_handler_test.go

Enhanced fakeLeaderForwarder mock to track leader IP changes and forward calls
TestRejectOrForwardLeaderQuery_LeadershipTransition - tests behavior when leadership changes (leader → follower → leader)
TestRejectOrForwardLeaderQuery_LeaderIPChange - tests that forwarder is updated when leader IP changes during follower state

Describe how you validated your changes

Additional Notes

cit-pr-commenter · 2025-12-01T17:19:24Z

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 02f5ae9e-d525-4a23-ba30-5d0fa5dfec40

Baseline: 92bf342
Comparison: 0169589
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	-0.56	[-3.55, +2.43]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	file_tree	memory utilization	+0.85	[+0.78, +0.92]	1	Logs
➖	quality_gate_idle	memory utilization	+0.56	[+0.51, +0.61]	1	Logs bounds checks dashboard
➖	docker_containers_memory	memory utilization	+0.51	[+0.43, +0.58]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	+0.43	[+0.38, +0.49]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.12	[-0.29, +0.52]	1	Logs
➖	ddot_metrics	memory utilization	+0.11	[-0.12, +0.34]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.08	[-0.29, +0.45]	1	Logs
➖	ddot_logs	memory utilization	+0.07	[+0.00, +0.14]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	+0.06	[-0.17, +0.29]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.03	[-0.02, +0.07]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.08, +0.08]	1	Logs
➖	otlp_ingest_metrics	memory utilization	+0.00	[-0.15, +0.15]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	-0.00	[-0.13, +0.12]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.14, +0.12]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.05	[-0.43, +0.34]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.15	[-0.31, +0.02]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.17	[-0.38, +0.04]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.22	[-0.26, -0.19]	1	Logs bounds checks dashboard
➖	otlp_ingest_logs	memory utilization	-0.24	[-0.34, -0.14]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	-0.43	[-0.64, -0.22]	1	Logs bounds checks dashboard
➖	docker_containers_cpu	% cpu utilization	-0.56	[-3.55, +2.43]	1	Logs
➖	quality_gate_logs	% cpu utilization	-1.30	[-2.75, +0.15]	1	Logs bounds checks dashboard
➖	tcp_syslog_to_blackhole	ingress throughput	-2.40	[-2.49, -2.32]	1	Logs

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:

Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.
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.
Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates 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_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_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_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_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.

agent-platform-auto-pr · 2025-12-02T01:51:35Z

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor f1a9f13

Successful checks

Info

	Quality gate	Delta	On disk size (MiB)	Delta	On wire size (MiB)
✅	agent_deb_amd64	$${+0.01}$$	$${705.43}$$ < $${706.32}$$	$${-0.02}$$	$${172.9}$$ < $${173.81}$$
✅	agent_deb_amd64_fips	$${+0}$$	$${700.76}$$ < $${701.16}$$	$${+0.05}$$	$${171.95}$$ < $${172.71}$$
✅	agent_heroku_amd64	$${+0.01}$$	$${327.44}$$ < $${327.69}$$	$${+0}$$	$${87.37}$$ < $${88.19}$$
✅	agent_msi	$${-0.1}$$	$${979.1}$$ < $${982.08}$$	$${+0.02}$$	$${141.85}$$ < $${143.01}$$
✅	agent_rpm_amd64	$${+0.01}$$	$${705.41}$$ < $${706.31}$$	$${-0.03}$$	$${175.96}$$ < $${176.86}$$
✅	agent_rpm_amd64_fips	$${+0}$$	$${700.74}$$ < $${701.15}$$	$${+0.02}$$	$${174.01}$$ < $${174.95}$$
✅	agent_rpm_arm64	$${+0.01}$$	$${691.08}$$ < $${691.67}$$	$${+0.01}$$	$${159.78}$$ < $${160.7}$$
✅	agent_rpm_arm64_fips	$${+0.01}$$	$${687.31}$$ < $${687.54}$$	$${+0.02}$$	$${159.29}$$ < $${160.1}$$
✅	agent_suse_amd64	$${+0.01}$$	$${705.41}$$ < $${706.31}$$	$${-0.03}$$	$${175.96}$$ < $${176.86}$$
✅	agent_suse_amd64_fips	$${+0}$$	$${700.74}$$ < $${701.15}$$	$${+0.02}$$	$${174.01}$$ < $${174.95}$$
✅	agent_suse_arm64	$${+0.01}$$	$${691.08}$$ < $${691.67}$$	$${+0.01}$$	$${159.78}$$ < $${160.7}$$
✅	agent_suse_arm64_fips	$${+0.01}$$	$${687.31}$$ < $${687.54}$$	$${+0.02}$$	$${159.29}$$ < $${160.1}$$
✅	docker_agent_amd64	$${+0.01}$$	$${767.74}$$ < $${768.66}$$	$${-0}$$	$${260.68}$$ < $${261.52}$$
✅	docker_agent_arm64	$${+0.01}$$	$${777.7}$$ < $${778.35}$$	$${+0.01}$$	$${250.86}$$ < $${251.72}$$
✅	docker_agent_jmx_amd64	$${+0.01}$$	$${958.62}$$ < $${959.54}$$	$${-0}$$	$${329.31}$$ < $${330.15}$$
✅	docker_agent_jmx_arm64	$${+0.01}$$	$${957.3}$$ < $${957.95}$$	$${+0.01}$$	$${315.49}$$ < $${316.35}$$
✅	docker_cluster_agent_amd64	$${-0}$$	$${178.89}$$ < $${179.28}$$	$${-0}$$	$${63.18}$$ < $${63.96}$$
✅	docker_cluster_agent_arm64	$${+0}$$	$${196.39}$$ < $${196.79}$$	$${-0}$$	$${59.9}$$ < $${60.69}$$
✅	docker_cws_instrumentation_amd64	$${0}$$	$${7.07}$$ < $${7.12}$$	$${+0}$$	$${2.95}$$ < $${3.29}$$
✅	docker_cws_instrumentation_arm64	$${-0}$$	$${6.69}$$ < $${6.92}$$	$${-0}$$	$${2.71}$$ < $${3.07}$$
✅	docker_dogstatsd_amd64	$${0}$$	$${38.66}$$ < $${39.3}$$	$${-0}$$	$${14.93}$$ < $${15.76}$$
✅	docker_dogstatsd_arm64	$${0}$$	$${37.3}$$ < $${37.94}$$	$${-0}$$	$${14.37}$$ < $${14.83}$$
✅	dogstatsd_deb_amd64	$${0}$$	$${29.88}$$ < $${30.53}$$	$${+0}$$	$${7.88}$$ < $${8.75}$$
✅	dogstatsd_deb_arm64	$${0}$$	$${28.39}$$ < $${29.11}$$	$${-0}$$	$${6.82}$$ < $${7.71}$$
✅	dogstatsd_rpm_amd64	$${0}$$	$${29.88}$$ < $${30.53}$$	$${-0}$$	$${7.89}$$ < $${8.76}$$
✅	dogstatsd_suse_amd64	$${0}$$	$${29.88}$$ < $${30.53}$$	$${-0}$$	$${7.89}$$ < $${8.76}$$
✅	iot_agent_deb_amd64	$${0}$$	$${42.61}$$ < $${43.19}$$	$${-0}$$	$${11.13}$$ < $${11.98}$$
✅	iot_agent_deb_arm64	$${0}$$	$${40.35}$$ < $${40.92}$$	$${+0}$$	$${9.58}$$ < $${10.45}$$
✅	iot_agent_deb_armhf	$${0}$$	$${40.25}$$ < $${40.86}$$	$${+0}$$	$${9.7}$$ < $${10.56}$$
✅	iot_agent_rpm_amd64	$${0}$$	$${42.61}$$ < $${43.19}$$	$${+0}$$	$${11.14}$$ < $${12.0}$$
✅	iot_agent_suse_amd64	$${0}$$	$${42.61}$$ < $${43.19}$$	$${+0}$$	$${11.14}$$ < $${12.0}$$

zhuminyi · 2025-12-02T13:32:04Z

/merge

dd-devflow-routing-codex · 2025-12-02T13:32:07Z

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zhuminyi · 2025-12-02T13:34:02Z

/merge --cancel

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zhuminyi · 2025-12-02T13:34:07Z

/remove

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gabedos

loop detection tests look good to me

zhuminyi · 2025-12-16T19:11:32Z

/merge

dd-devflow-routing-codex · 2025-12-16T19:11:37Z

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The expected merge time in main is approximately 53m (p90).

2025-12-16 19:53:31 UTC ❌ MergeQueue: The build pipeline contains failing jobs for this merge request

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zhuminyi · 2025-12-16T21:20:24Z

/merge

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2025-12-16 22:56:40 UTC ℹ️ MergeQueue: This merge request was merged

…nt leader election (#43680) ### What does this PR do? - Add unit tests for cluster agent leader election and leadership transitions - Fix bug in LeaderForwarder.Forward() where loop detection didn't return after writing error ### Motivation Fixed a bug in pkg/clusteragent/api/leader_forwarder.go where loop detection (via X-DCA-Follower-Forwarded header) wrote an HTTP 508 error but continued to forward the request to the leader anyway. Added missing return statement to properly short-circuit the request. New Tests pkg/clusteragent/api/leader_forwarder_test.go - TestLeaderForwarder_SetLeaderIP - tests leader IP setting, updating, and clearing - TestLeaderForwarder_Forward_NilProxy - tests behavior when no leader is configured - TestLeaderForwarder_Forward_LoopDetection - tests that forwarding loops are properly detected and rejected - TestLeaderForwarder_Forward_WithLeader - tests successful forwarding to leader pkg/clusteragent/api/leader_handler_test.go - Enhanced fakeLeaderForwarder mock to track leader IP changes and forward calls - TestRejectOrForwardLeaderQuery_LeadershipTransition - tests behavior when leadership changes (leader → follower → leader) - TestRejectOrForwardLeaderQuery_LeaderIPChange - tests that forwarder is updated when leader IP changes during follower state ### Describe how you validated your changes ### Additional Notes Co-authored-by: minyi.zhu <minyi.zhu@datadoghq.com>

github-actions bot added medium review PR review might take time team/container-platform The Container Platform Team labels Dec 1, 2025

zhuminyi force-pushed the unittest_dca_leader_handler branch 2 times, most recently from 3370331 to 0982106 Compare December 1, 2025 16:06

zhuminyi added this to the 7.75.0 milestone Dec 1, 2025

zhuminyi added changelog/no-changelog No changelog entry needed qa/skip-qa labels Dec 1, 2025

zhuminyi force-pushed the unittest_dca_leader_handler branch 2 times, most recently from 1827ade to 6cdffc3 Compare December 1, 2025 16:23

github-actions bot added short review PR is simple enough to be reviewed quickly and removed medium review PR review might take time labels Dec 1, 2025

zhuminyi force-pushed the unittest_dca_leader_handler branch 2 times, most recently from 0cd8101 to a4f612e Compare December 2, 2025 01:08

github-actions bot added medium review PR review might take time and removed short review PR is simple enough to be reviewed quickly labels Dec 2, 2025

zhuminyi changed the title ~~Add unit test for testing cluster agent leader election~~ Fix loop detection bug and add unit tests for cluster agent leader election Dec 2, 2025

zhuminyi changed the title ~~Fix loop detection bug and add unit tests for cluster agent leader election~~ [CONTP-849] Fix loop detection bug and add unit tests for cluster agent leader election Dec 2, 2025

zhuminyi added qa/done QA done before merge and regressions are covered by tests and removed qa/skip-qa labels Dec 2, 2025

zhuminyi marked this pull request as ready for review December 2, 2025 01:59

zhuminyi requested a review from a team as a code owner December 2, 2025 01:59

zhuminyi force-pushed the unittest_dca_leader_handler branch 2 times, most recently from 185f729 to effca9e Compare December 2, 2025 10:42

zhuminyi force-pushed the unittest_dca_leader_handler branch from effca9e to 8e083da Compare December 2, 2025 15:13

zhuminyi added 2 commits December 8, 2025 11:06

Add unit test for testing cluster agent leader election

9f09c9b

Update leader_forwarder and unit test

0169589

zhuminyi force-pushed the unittest_dca_leader_handler branch from 8e083da to 0169589 Compare December 8, 2025 16:06

gabedos approved these changes Dec 16, 2025

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dd-mergequeue bot merged commit b09cd03 into main Dec 16, 2025
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dd-mergequeue bot deleted the unittest_dca_leader_handler branch December 16, 2025 22:56

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What does this PR do?

Motivation

Describe how you validated your changes

Additional Notes

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Regression Detector

Regression Detector Results

Optimization Goals: ✅ No significant changes detected

Experiments ignored for regressions

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

CI Pass/Fail Decision

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Static quality checks

Info

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