[CNM-4667] Fix several flaky TestTracerSuite tests. by jmw51798 · Pull Request #46589 · DataDog/datadog-agent

jmw51798 · 2026-02-17T21:20:59Z

What does this PR do?

Fixes several flaky eBPFless tests in TestTracerSuite.

TestTracerSuite/eBPFless/TestShortWrite — "couldn't find connection used by short write"
- (Real bug.) Fixes updateTCPStats() so it no longer overcounts SentBytes when the kernel retransmits TCP segments that partially overlap with previously-counted data. We now only add the new bytes beyond the sequence high‑water mark.
TestTracerSuite/eBPFless/TestShortWrite — "resource temporarily unavailable"
- (Test-only bug.) Fixes the TestShortWrite write loop to correctly handle the case where the send buffer is completely full and a write returns zero bytes with resource temporarily unavailable.
TestTracerSuite/eBPFless/TestTCPRTT — "write: bad file descriptor"
- (Test-only bug.) Fixes an fd lifecycle issue in TestShortWrite: The original TestShortWrite had a triple-close on the socket fd (defer syscall.Close, explicit unix.Close, and the os.NewFile GC finalizer). After the first close, the kernel could reuse the fd number, so later closes would clobber unrelated fds in other tests. Fixed by consolidating ownership into a single t.Cleanup that does f.Close().

Motivation

pkg/network/tracer.TestTracerSuite has many flaky test failures in CI.

Describe how you validated your changes

TestShortWrite connection‑not‑found

# Reproduced by running the following on a vagrant VM.
# Validated after the fix was applied that this failure no longer occurred.

sudo go test -v -count 1000 -failfast -tags linux_bpf,test ./pkg/network/tracer -run 'TestTracerSuite/eBPFless/TestShortWrite'

=== RUN   TestTracerSuite/eBPFless/TestShortWrite
1771024760834621303 [Warn] not starting resolv.conf container store, because it depends on process event monitoring which is disabled
    tracer_linux_test.go:1979: sent: 5000
    tracer_linux_test.go:1979: sent: 10000
    tracer_linux_test.go:1979: sent: 15000
    tracer_linux_test.go:1979: sent: 20000
    tracer_linux_test.go:1979: sent: 25000
    tracer_linux_test.go:1979: sent: 30000
    tracer_linux_test.go:1979: sent: 35000
    tracer_linux_test.go:1979: sent: 40000
    tracer_linux_test.go:1979: sent: 42741
    tracer_linux_test.go:1997:
        	Error Trace:	/git/datadog-agent/pkg/network/tracer/tracer_linux_test.go:2001
        	            				/root/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.25.7.linux-arm64/src/runtime/asm_arm64.s:1268
        	Error:      	Should be true
    tracer_linux_test.go:1997:
        	Error Trace:	/git/datadog-agent/pkg/network/tracer/tracer_linux_test.go:1997
        	Error:      	Condition never satisfied
        	Test:       	TestTracerSuite/eBPFless/TestShortWrite
        	Messages:   	couldn't find connection used by short write
--- FAIL: TestTracerSuite (10.16s)
    --- FAIL: TestTracerSuite/eBPFless (10.16s)
        --- FAIL: TestTracerSuite/eBPFless/TestShortWrite (10.16s)

TestShortWrite resource temporarily unavailable

# Reproduced by running the following on a vagrant VM (with fix for #1)
# Validated after the fix was applied that this failure no longer occurred.

sudo go test -v -count 1000 -failfast -tags linux_bpf,test ./pkg/network/tracer -run 'TestTracerSuite/eBPFless/TestShortWrite'

=== RUN   TestTracerSuite/eBPFless/TestShortWrite
1771025049854166657 [Warn] not starting resolv.conf container store, because it depends on process event monitoring which is disabled
    tracer_linux_test.go:1981: sent: 5000
    tracer_linux_test.go:1981: sent: 10000
    tracer_linux_test.go:1981: sent: 15000
    tracer_linux_test.go:1978:
        	Error Trace:	/git/datadog-agent/pkg/network/tracer/tracer_linux_test.go:1978
        	Error:      	Received unexpected error:
        	            	resource temporarily unavailable
        	Test:       	TestTracerSuite/eBPFless/TestShortWrite
--- FAIL: TestTracerSuite (1.22s)
    --- FAIL: TestTracerSuite/eBPFless (1.22s)
        --- FAIL: TestTracerSuite/eBPFless/TestShortWrite (1.21s)

TestTCPRTT write: bad file descriptor

# Reproduced by running the following on a vagrant VM (with fixes for #1 and #2)
# Validated after the fix was applied that this failure no longer occurred.

sudo go test -v -count 100 -failfast -tags linux_bpf,test ./pkg/network/tracer -run 'TestTracerSuite/eBPFless/(TestShortWrite|TestTCPRTT)'

=== RUN   TestTracerSuite/eBPFless/TestTCPRTT
1771024042054119651 [Warn] not starting resolv.conf container store, because it depends on process event monitoring which is disabled
    tracer_linux_test.go:316:
        	Error Trace:	/git/datadog-agent/pkg/network/tracer/tracer_linux_test.go:316
        	Error:      	Received unexpected error:
        	            	write tcp 127.0.0.1:44304->127.0.0.1:43449: write: bad file descriptor
        	Test:       	TestTracerSuite/eBPFless/TestTCPRTT
--- FAIL: TestTracerSuite (1.30s)
    --- FAIL: TestTracerSuite/eBPFless (1.30s)
        --- PASS: TestTracerSuite/eBPFless/TestShortWrite (0.15s)
        --- FAIL: TestTracerSuite/eBPFless/TestTCPRTT (1.16s)

…retransmitted TCP segments that partially overlapped with previously-counted data.

…reused fd during a later test.

agent-platform-auto-pr · 2026-02-17T22:00:09Z

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 6718cd6
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	docker_agent_arm64	+7.04 KiB (0.00% increase)	819.767 → 819.774 → 828.520

30 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	755.750 MiB
✅	agent_deb_amd64_fips	714.674 MiB
✅	agent_heroku_amd64	323.406 MiB
✅	agent_msi	622.109 MiB
✅	agent_rpm_amd64	755.734 MiB
✅	agent_rpm_amd64_fips	714.658 MiB
✅	agent_rpm_arm64	733.991 MiB
✅	agent_rpm_arm64_fips	695.822 MiB
✅	agent_suse_amd64	755.734 MiB
✅	agent_suse_amd64_fips	714.658 MiB
✅	agent_suse_arm64	733.991 MiB
✅	agent_suse_arm64_fips	695.822 MiB
✅	docker_agent_amd64	816.798 MiB
✅	docker_agent_jmx_amd64	1007.710 MiB
✅	docker_agent_jmx_arm64	999.461 MiB
✅	docker_cluster_agent_amd64	190.358 MiB
✅	docker_cluster_agent_arm64	205.797 MiB
✅	docker_cws_instrumentation_amd64	7.135 MiB
✅	docker_cws_instrumentation_arm64	6.689 MiB
✅	docker_dogstatsd_amd64	38.488 MiB
✅	docker_dogstatsd_arm64	36.812 MiB
✅	dogstatsd_deb_amd64	29.712 MiB
✅	dogstatsd_deb_arm64	27.868 MiB
✅	dogstatsd_rpm_amd64	29.712 MiB
✅	dogstatsd_suse_amd64	29.712 MiB
✅	iot_agent_deb_amd64	42.912 MiB
✅	iot_agent_deb_arm64	40.014 MiB
✅	iot_agent_deb_armhf	40.584 MiB
✅	iot_agent_rpm_amd64	42.913 MiB
✅	iot_agent_suse_amd64	42.913 MiB

On-wire sizes (compressed)

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-13.11 KiB (0.01% reduction)	185.178 → 185.166 → 186.090
✅	agent_deb_amd64_fips	+12.35 KiB (0.01% increase)	176.007 → 176.019 → 180.330
✅	agent_heroku_amd64	+4.76 KiB (0.01% increase)	87.216 → 87.221 → 88.440
✅	agent_msi	+28.0 KiB (0.02% increase)	138.324 → 138.352 → 143.470
✅	agent_rpm_amd64	-15.66 KiB (0.01% reduction)	187.071 → 187.056 → 189.170
✅	agent_rpm_amd64_fips	neutral	178.106 MiB → 181.060
✅	agent_rpm_arm64	+27.13 KiB (0.02% increase)	169.211 → 169.237 → 170.020
✅	agent_rpm_arm64_fips	+9.23 KiB (0.01% increase)	162.123 → 162.132 → 164.130
✅	agent_suse_amd64	-15.66 KiB (0.01% reduction)	187.071 → 187.056 → 189.170
✅	agent_suse_amd64_fips	neutral	178.106 MiB → 181.060
✅	agent_suse_arm64	+27.13 KiB (0.02% increase)	169.211 → 169.237 → 170.020
✅	agent_suse_arm64_fips	+9.23 KiB (0.01% increase)	162.123 → 162.132 → 164.130
✅	docker_agent_amd64	neutral	277.431 MiB → 279.410
✅	docker_agent_arm64	-9.97 KiB (0.00% reduction)	264.760 → 264.750 → 267.960
✅	docker_agent_jmx_amd64	neutral	346.081 MiB → 348.040
✅	docker_agent_jmx_arm64	neutral	329.389 MiB → 332.560
✅	docker_cluster_agent_amd64	neutral	66.501 MiB → 67.220
✅	docker_cluster_agent_arm64	neutral	62.550 MiB → 63.640
✅	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	14.235 MiB → 14.830
✅	dogstatsd_deb_amd64	neutral	7.850 MiB → 8.790
✅	dogstatsd_deb_arm64	neutral	6.738 MiB → 7.710
✅	dogstatsd_rpm_amd64	neutral	7.862 MiB → 8.800
✅	dogstatsd_suse_amd64	neutral	7.862 MiB → 8.800
✅	iot_agent_deb_amd64	neutral	11.261 MiB → 12.040
✅	iot_agent_deb_arm64	neutral	9.625 MiB → 10.450
✅	iot_agent_deb_armhf	neutral	9.826 MiB → 10.620
✅	iot_agent_rpm_amd64	-2.29 KiB (0.02% reduction)	11.280 → 11.277 → 12.060
✅	iot_agent_suse_amd64	-2.29 KiB (0.02% reduction)	11.280 → 11.277 → 12.060

cit-pr-commenter-54b7da · 2026-02-17T22:13:44Z

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 726aff87-943f-4bdb-afd5-db0c856d79f8

Baseline: 6718cd6
Comparison: 1e4ed97
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	+0.09	[-2.99, +3.18]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	tcp_syslog_to_blackhole	ingress throughput	+1.04	[+0.96, +1.12]	1	Logs
➖	ddot_metrics	memory utilization	+0.69	[+0.48, +0.91]	1	Logs
➖	file_tree	memory utilization	+0.12	[+0.07, +0.17]	1	Logs
➖	docker_containers_cpu	% cpu utilization	+0.09	[-2.99, +3.18]	1	Logs
➖	quality_gate_idle	memory utilization	+0.09	[+0.05, +0.14]	1	Logs bounds checks dashboard
➖	file_to_blackhole_500ms_latency	egress throughput	+0.07	[-0.32, +0.46]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	+0.02	[-0.11, +0.15]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.01	[-0.03, +0.06]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.01	[-0.40, +0.43]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.01	[-0.49, +0.51]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.13, +0.12]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.01	[-0.10, +0.08]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.09	[-0.12, -0.05]	1	Logs bounds checks dashboard
➖	otlp_ingest_metrics	memory utilization	-0.14	[-0.30, +0.02]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	-0.20	[-0.40, +0.01]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.21	[-0.26, -0.15]	1	Logs
➖	ddot_logs	memory utilization	-0.25	[-0.31, -0.18]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.26	[-0.45, -0.08]	1	Logs
➖	docker_containers_memory	memory utilization	-0.31	[-0.39, -0.24]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.34	[-0.57, -0.11]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.56	[-0.72, -0.41]	1	Logs
➖	quality_gate_logs	% cpu utilization	-0.84	[-2.37, +0.69]	1	Logs bounds checks dashboard
➖	otlp_ingest_logs	memory utilization	-0.89	[-1.00, -0.78]	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 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 lost_bytes: 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 intake_connections: 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.
quality_gate_logs, 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.

AmitaiBl · 2026-02-18T00:32:33Z

+			if st.hasSentPacket && isSeqBefore(tcp.Seq, st.maxSeqSent) {
+				overlap = uint64(st.maxSeqSent - tcp.Seq)
+			}
+			if uint64(payloadLen) > overlap {


should you also check if overlap is bigger than 0?

I don't think that's needed. overlap defaults to zero and is only set to a positive value when there is overlap (isSeqBefore(tcp.Seq, st.maxSeqSent)). When overlap is 0, which is the common case, the full payloadLen is added to SentBytes.

pimlu

Awesome!

jmw51798 · 2026-02-18T19:42:01Z

/merge

gh-worker-devflow-routing-ef8351 · 2026-02-18T19:42:05Z

View all feedbacks in Devflow UI.

2026-02-18 19:42:05 UTC ℹ️ Start processing command /merge

2026-02-18 19:42:10 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 2h (p90).

2026-02-18 20:20:30 UTC ℹ️ MergeQueue: This merge request was merged

jmw51798 added 4 commits February 17, 2026 14:04

Fix updateTCPStats() to avoid overcounting SentBytes when the kernel …

aabba2f

…retransmitted TCP segments that partially overlapped with previously-counted data.

Add TestPartialOverlapRetransmit.

e9e9abc

Handle short write when send buffer is completely full.

b5068e4

Fix fd handling in TestShortWrite to avoid unintentionally closing a …

1e4ed97

…reused fd during a later test.

github-actions Bot added the component/system-probe label Feb 17, 2026

dd-octo-sts Bot added the internal Identify a non-fork PR label Feb 17, 2026

github-actions Bot added the short review PR is simple enough to be reviewed quickly label Feb 17, 2026

dd-octo-sts Bot added the team/cloud-network-monitoring label Feb 17, 2026

jmw51798 added changelog/no-changelog No changelog entry needed qa/done QA done before merge and regressions are covered by tests labels Feb 17, 2026

jmw51798 marked this pull request as ready for review February 17, 2026 23:43

jmw51798 requested a review from a team as a code owner February 17, 2026 23:43

jmw51798 requested review from charan-manjunath and pimlu and removed request for charan-manjunath February 17, 2026 23:43

AmitaiBl reviewed Feb 18, 2026

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github-actions Bot added medium review PR review might take time and removed short review PR is simple enough to be reviewed quickly labels Feb 18, 2026

pimlu approved these changes Feb 18, 2026

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gh-worker-dd-mergequeue-cf854d Bot merged commit 31d06e7 into main Feb 18, 2026
423 of 427 checks passed

gh-worker-dd-mergequeue-cf854d Bot deleted the jmw/flaky-testtracersuite-testshortwrite-and-testtcprtt2 branch February 18, 2026 20:20

github-actions Bot added this to the 7.77.0 milestone Feb 18, 2026

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[CNM-4667] Fix several flaky TestTracerSuite tests.#46589

[CNM-4667] Fix several flaky TestTracerSuite tests.#46589
gh-worker-dd-mergequeue-cf854d[bot] merged 4 commits intomainfrom
jmw/flaky-testtracersuite-testshortwrite-and-testtcprtt2

jmw51798 commented Feb 17, 2026 •

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Info

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cit-pr-commenter-54b7da Bot commented Feb 17, 2026

Experiments ignored for regressions

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

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What does this PR do?

Motivation

Describe how you validated your changes

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Static quality checks

Info

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cit-pr-commenter-54b7da Bot commented Feb 17, 2026

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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