fix(system-probe-lite): log full error chain to surface EPERM and other causes by vitkyrka · Pull Request #50538 · DataDog/datadog-agent

vitkyrka · 2026-05-08T09:59:01Z

What does this PR do?

In `pkg/discovery/module/rust/src/main.rs`, three `error!`/`warn!` call sites now use the `{:#}` alternate format (via `anyhow`) so the full error cause chain is included in the log line.

Call site	Before	After
`serve_connection` failure	`Error serving connection: error writing a body to connection`	`Error serving connection: error writing a body to connection: Operation not permitted (os error 1)`
`handle_request` failure	`Request handling failed: `	`Request handling failed: : `
`drop_capabilities` failure	`Failed to restrict capabilities: ; …`	`Failed to restrict capabilities: : ; …`

For `hyper::Error` (the connection error), wrapping in `anyhow::Error::new(err)` is required because `hyper::Error`'s own `Display` impl does not traverse `.source()`. For the two `anyhow::Error` sites the change is simply adding `#` to the format specifier.

Motivation

While debugging helm-charts#2634, which added `writev`, `shutdown`, and `chown` to the system-probe seccomp allowlist for SPL, the only log produced was:

SYS-PROBE-LITE | ERROR | Error serving connection: error writing a body to connection

The underlying cause (`Operation not permitted (os error 1)`) was invisible, making `strace` necessary to identify the blocked syscall. With this fix the EPERM — or any other root cause — appears directly in the log.

Describe how you validated your changes

`bazel build --config=lint //pkg/discovery/module/rust/...` passes
`bazel test //pkg/discovery/module/rust/...` — all 7 tests pass
Manual test for the `serve_connection` path: ran SPL with an `LD_PRELOAD` shim that makes every `writev(2)` call return `EPERM`, then sent a GET request to the socket:
- Before: `Error serving connection: error writing a body to connection`
- After: `Error serving connection: error writing a body to connection: Operation not permitted (os error 1)`
Manual test for the `handle_request` path: ran SPL with a temporary chained-error injection (`anyhow!("inner").context("outer")`) at the top of `handle_request`:
- Before: `Request handling failed: outer`
- After: `Request handling failed: outer: inner`

…rors `hyper::Error` and `anyhow::Error` both implement `Display` to show only the top-level message. The `{:#}` alternate format on `anyhow::Error` traverses the full `.source()` chain, joining all levels with `: `. Three call sites updated: - "Error serving connection" (hyper::Error wrapped via anyhow::Error::new) - "Request handling failed" (already anyhow::Error, just needed `#`) - "Failed to restrict capabilities" (same) Without the fix, a seccomp EPERM on `writev` logged only: Error serving connection: error writing a body to connection After: Error serving connection: error writing a body to connection: Operation not permitted (os error 1) Manual test (request handler path): Before: Request handling failed: request processing failed After: Request handling failed: request processing failed: inner cause detail This was surfaced while debugging helm-charts#2634, which added `writev`, `shutdown`, and `chown` to the system-probe seccomp profile for SPL. Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

dd-octo-sts · 2026-05-08T10:26:11Z

Files inventory check summary

File checks results against ancestor ef81861a:

Results for datadog-agent_7.80.0~devel.git.601.9685706.pipeline.112154034-1_amd64.deb:

No change detected

dd-octo-sts · 2026-05-08T10:34:55Z

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor ef81861
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	+4.0 KiB (0.00% increase)	742.626 → 742.630 → 750.310
✅	agent_deb_amd64_fips	+4.0 KiB (0.00% increase)	700.654 → 700.658 → 702.690
✅	agent_rpm_amd64	+4.0 KiB (0.00% increase)	742.610 → 742.614 → 750.280
✅	agent_rpm_amd64_fips	+4.0 KiB (0.00% increase)	700.637 → 700.641 → 702.670
✅	agent_suse_amd64	+4.0 KiB (0.00% increase)	742.610 → 742.614 → 750.280
✅	agent_suse_amd64_fips	+4.0 KiB (0.00% increase)	700.637 → 700.641 → 702.670
✅	docker_agent_amd64	+5.56 KiB (0.00% increase)	802.814 → 802.819 → 805.870
✅	docker_agent_jmx_amd64	+4.0 KiB (0.00% increase)	993.734 → 993.738 → 996.590

24 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_heroku_amd64	309.245 MiB
✅	agent_rpm_arm64	720.515 MiB
✅	agent_rpm_arm64_fips	681.630 MiB
✅	agent_suse_arm64	720.515 MiB
✅	agent_suse_arm64_fips	681.630 MiB
✅	docker_agent_arm64	805.552 MiB
✅	docker_agent_jmx_arm64	985.250 MiB
✅	docker_cluster_agent_amd64	206.662 MiB
✅	docker_cluster_agent_arm64	220.697 MiB
✅	docker_cws_instrumentation_amd64	7.142 MiB
✅	docker_cws_instrumentation_arm64	6.689 MiB
✅	docker_host_profiler_amd64	302.171 MiB
✅	docker_host_profiler_arm64	313.666 MiB
✅	docker_dogstatsd_amd64	39.507 MiB
✅	docker_dogstatsd_arm64	37.691 MiB
✅	dogstatsd_deb_amd64	30.169 MiB
✅	dogstatsd_deb_arm64	28.294 MiB
✅	dogstatsd_rpm_amd64	30.169 MiB
✅	dogstatsd_suse_amd64	30.169 MiB
✅	iot_agent_deb_amd64	44.518 MiB
✅	iot_agent_deb_arm64	41.494 MiB
✅	iot_agent_deb_armhf	42.230 MiB
✅	iot_agent_rpm_amd64	44.518 MiB
✅	iot_agent_suse_amd64	44.518 MiB

cit-pr-commenter-54b7da · 2026-05-08T10:48:38Z

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: eba59ee8-a484-4a8d-b554-79c392c1b570

Baseline: aeea69d
Comparison: d4e9d5a
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	+1.46	[-1.51, +4.42]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	docker_containers_cpu	% cpu utilization	+1.46	[-1.51, +4.42]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	+0.70	[+0.53, +0.86]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	+0.32	[+0.27, +0.37]	1	Logs
➖	docker_containers_memory	memory utilization	+0.10	[+0.00, +0.20]	1	Logs
➖	otlp_ingest_logs	memory utilization	+0.04	[-0.06, +0.15]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.03	[-0.38, +0.44]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.09, +0.11]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.01	[-0.44, +0.45]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.01	[-0.50, +0.51]	1	Logs
➖	ddot_metrics	memory utilization	+0.01	[-0.19, +0.21]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	+0.00	[-0.20, +0.20]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.20, +0.19]	1	Logs
➖	file_tree	memory utilization	-0.04	[-0.09, +0.01]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.11	[-0.25, +0.03]	1	Logs
➖	otlp_ingest_metrics	memory utilization	-0.24	[-0.39, -0.08]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.25	[-0.43, -0.07]	1	Logs
➖	quality_gate_idle	memory utilization	-0.26	[-0.31, -0.21]	1	Logs bounds checks dashboard
➖	tcp_syslog_to_blackhole	ingress throughput	-0.32	[-0.51, -0.13]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.50	[-0.54, -0.47]	1	Logs bounds checks dashboard
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.51	[-0.75, -0.28]	1	Logs
➖	quality_gate_logs	% cpu utilization	-0.61	[-1.59, +0.37]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-0.70	[-0.95, -0.44]	1	Logs bounds checks dashboard
➖	ddot_logs	memory utilization	-1.02	[-1.09, -0.95]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	docker_containers_cpu	simple_check_run	10/10	674 ≥ 26
✅	docker_containers_memory	memory_usage	10/10	241.49MiB ≤ 370MiB
✅	docker_containers_memory	simple_check_run	10/10	728 ≥ 26
✅	file_to_blackhole_0ms_latency	memory_usage	10/10	0.16GiB ≤ 1.20GiB
✅	file_to_blackhole_0ms_latency	missed_bytes	10/10	0B = 0B
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10	0.21GiB ≤ 1.20GiB
✅	file_to_blackhole_1000ms_latency	missed_bytes	10/10	0B = 0B
✅	file_to_blackhole_100ms_latency	memory_usage	10/10	0.17GiB ≤ 1.20GiB
✅	file_to_blackhole_100ms_latency	missed_bytes	10/10	0B = 0B
✅	file_to_blackhole_500ms_latency	memory_usage	10/10	0.19GiB ≤ 1.20GiB
✅	file_to_blackhole_500ms_latency	missed_bytes	10/10	0B = 0B
✅	quality_gate_idle	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	141.53MiB ≤ 147MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	470.79MiB ≤ 495MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	4 ≤ 6	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	173.26MiB ≤ 195MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	349.45 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	4 ≤ 6	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	362.40MiB ≤ 430MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	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_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_logs, 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 missed_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_metrics_logs, bounds check missed_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.

datadog-datadog-prod-us1 · 2026-05-08T12:33:52Z

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 50.31% (+0.15%)

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 9685706 | Docs | Datadog PR Page | Give us feedback!}

…er causes (#50538) ### What does this PR do? In \`pkg/discovery/module/rust/src/main.rs\`, three \`error!\`/\`warn!\` call sites now use the \`{:#}\` alternate format (via \`anyhow\`) so the full error cause chain is included in the log line. | Call site | Before | After | |---|---|---| | \`serve_connection\` failure | \`Error serving connection: error writing a body to connection\` | \`Error serving connection: error writing a body to connection: Operation not permitted (os error 1)\` | | \`handle_request\` failure | \`Request handling failed: <top-level>\` | \`Request handling failed: <top-level>: <cause>\` | | \`drop_capabilities\` failure | \`Failed to restrict capabilities: <top-level>; …\` | \`Failed to restrict capabilities: <top-level>: <cause>; …\` | For \`hyper::Error\` (the connection error), wrapping in \`anyhow::Error::new(err)\` is required because \`hyper::Error\`'s own \`Display\` impl does not traverse \`.source()\`. For the two \`anyhow::Error\` sites the change is simply adding \`#\` to the format specifier. ### Motivation While debugging [helm-charts#2634](DataDog/helm-charts#2634), which added \`writev\`, \`shutdown\`, and \`chown\` to the system-probe seccomp allowlist for SPL, the only log produced was: ``` SYS-PROBE-LITE | ERROR | Error serving connection: error writing a body to connection ``` The underlying cause (\`Operation not permitted (os error 1)\`) was invisible, making \`strace\` necessary to identify the blocked syscall. With this fix the EPERM — or any other root cause — appears directly in the log. ### Describe how you validated your changes - \`bazel build --config=lint //pkg/discovery/module/rust/...\` passes - \`bazel test //pkg/discovery/module/rust/...\` — all 7 tests pass - Manual test for the \`serve_connection\` path: ran SPL with an \`LD_PRELOAD\` shim that makes every \`writev(2)\` call return \`EPERM\`, then sent a GET request to the socket: - **Before:** \`Error serving connection: error writing a body to connection\` - **After:** \`Error serving connection: error writing a body to connection: Operation not permitted (os error 1)\` - Manual test for the \`handle_request\` path: ran SPL with a temporary chained-error injection (\`anyhow!("inner").context("outer")\`) at the top of \`handle_request\`: - **Before:** \`Request handling failed: outer\` - **After:** \`Request handling failed: outer: inner\` Co-authored-by: vincent.whitchurch <[email protected]>

vitkyrka added changelog/no-changelog No changelog entry needed qa/done QA done before merge and regressions are covered by tests team/agent-discovery labels May 8, 2026

github-actions Bot added the component/system-probe label May 8, 2026

dd-octo-sts Bot added the internal Identify a non-fork PR label May 8, 2026

github-actions Bot added the short review PR is simple enough to be reviewed quickly label May 8, 2026

vitkyrka marked this pull request as ready for review May 8, 2026 10:14

vitkyrka requested a review from a team as a code owner May 8, 2026 10:14

martavicentenavarro approved these changes May 8, 2026

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gh-worker-dd-mergequeue-cf854d Bot merged commit d4e9d5a into main May 8, 2026
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gh-worker-dd-mergequeue-cf854d Bot deleted the vitkyrka/disco-error branch May 8, 2026 13:04

github-actions Bot added this to the 7.80.0 milestone May 8, 2026

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fix(system-probe-lite): log full error chain to surface EPERM and other causes#50538

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Experiments ignored for regressions

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

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Files inventory check summary

Results for datadog-agent_7.80.0~devel.git.601.9685706.pipeline.112154034-1_amd64.deb:

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Static quality checks

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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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