[AGENTRUN-909] Handle tcp probes in trace-loader

[pgimalac]

What does this PR do?

Update the trace-loader to handle TCP probes to avoid waking up the trace-agent. This behavior is controlled by a config flag (disabled by default).

Motivation

The default k8s setup has TCP probes for the APM socket, which would make the loader exec the trace-agent.

Describe how you validated your changes

Tested locally with kind and a modified version of the helm chart (the current version doesn't run the trace-loader process). This feature will be enabled internally to ensure proper testing. This is disabled by default, so not risk for users.

Additional Notes

For a few more implementation details, when enabled the loader can now accepts one "client" connection on the TCP socket, and checks if it is closed or if there is data to read. If the connection is closed, it is removed and it starts waiting again. If there is data to read, it execs the trace-agent, passing the socket like for other file descriptors. If another client tries to connect before the first is closed, the trace-agent is started. If any error happens at any time, the trace-agent is started.

This makes the implementation less trivial (in particular all this logic runs in a loop, with many conditions breaking out of it, which doesn't help), but is the only way to support kubernetes setup without just changing the probe.

Example run

Here are the debug logs to help understand the execution (using kind and a modified version of the helm chart to run the trace-loader, with the related config flags enabled).

Initial logs:

TRACE-LOADER | INFO | (cmd/loader/main_nix.go:311 in getListeners) | Listening to TCP receiver at port 8126...
TRACE-LOADER | INFO | (cmd/loader/main_nix.go:333 in getListeners) | Listening to unix receiver at path /var/run/datadog/apm.socket
TRACE-LOADER | INFO | (cmd/loader/main_nix.go:371 in getListeners) | Trace-agent OTLP receiver is disabled
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:117 in main) | DD_APM_NET_RECEIVER_FD file descriptor is 9
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:117 in main) | DD_APM_UNIX_RECEIVER_FD file descriptor is 11
TRACE-LOADER | INFO | (cmd/loader/main_nix.go:133 in main) | Polling... [{Fd:9 Events:1 Revents:0} {Fd:11 Events:1 Revents:0}]

When the logic is enabled, the probe causes the following pattern:

TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:142 in main) | Events received on 1 sockets
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:147 in main) | Socket 9 has events POLLIN
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:227 in main) | Accepted connection on TCP listener: 7
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:142 in main) | Events received on 1 sockets
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:147 in main) | Socket 7 has events POLLIN
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:197 in main) | TCP client closed connection, closing file descriptor 7

When data is received, this happens:

TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:142 in main) | Events received on 1 sockets
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:147 in main) | Socket 9 has events POLLIN
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:227 in main) | Accepted connection on TCP listener: 6
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:142 in main) | Events received on 1 sockets
TRACE-LOADER | DEBUG | (cmd/loader/main_nix.go:147 in main) | Socket 6 has events POLLIN
TRACE-LOADER | INFO | (cmd/loader/main_nix.go:192 in main) | TCP client sent data, executing trace-agent...
TRACE-LOADER | INFO | (cmd/loader/main_nix.go:261 in execOrExit) | Starting the trace-agent...

[agent-platform-auto-pr[bot]]

Static quality checks

✅ Please find below the results from static quality gates Comparison made with ancestor 160282b4b9b0b82bb5f265671ba206cbe4d6093b

Successful checks

Info

	Quality gate	Delta	On disk size (MiB)	Delta	On wire size (MiB)
✅	agent_deb_amd64	$${-0.28}$$	$${705.88}$$ < $${707.13}$$	$${-0}$$	$${173.23}$$ < $${174.16}$$
✅	agent_deb_amd64_fips	$${-0.28}$$	$${702.09}$$ < $${702.86}$$	$${+0.02}$$	$${172.55}$$ < $${173.5}$$
✅	agent_heroku_amd64	$${+0.01}$$	$${327.52}$$ < $${327.92}$$	$${+0.01}$$	$${87.23}$$ < $${88.21}$$
✅	agent_msi	$${+0.01}$$	$${570.44}$$ < $${982.08}$$	$${+0.02}$$	$${142.49}$$ < $${143.49}$$
✅	agent_rpm_amd64	$${-0.28}$$	$${705.86}$$ < $${707.12}$$	$${-0.11}$$	$${176.33}$$ < $${177.29}$$
✅	agent_rpm_amd64_fips	$${-0.28}$$	$${702.08}$$ < $${702.85}$$	$${-0.2}$$	$${175.1}$$ < $${176.32}$$
✅	agent_rpm_arm64	$${-0.28}$$	$${687.56}$$ < $${691.67}$$	$${-0.09}$$	$${159.39}$$ < $${160.7}$$
✅	agent_rpm_arm64_fips	$${-0.28}$$	$${684.61}$$ < $${687.54}$$	$${-0.05}$$	$${159.16}$$ < $${160.11}$$
✅	agent_suse_amd64	$${-0.28}$$	$${705.86}$$ < $${707.12}$$	$${-0.11}$$	$${176.33}$$ < $${177.29}$$
✅	agent_suse_amd64_fips	$${-0.28}$$	$${702.08}$$ < $${702.85}$$	$${-0.2}$$	$${175.1}$$ < $${176.32}$$
✅	agent_suse_arm64	$${-0.28}$$	$${687.56}$$ < $${691.67}$$	$${-0.09}$$	$${159.39}$$ < $${160.7}$$
✅	agent_suse_arm64_fips	$${-0.28}$$	$${684.61}$$ < $${687.54}$$	$${-0.05}$$	$${159.16}$$ < $${160.11}$$
✅	docker_agent_amd64	$${-0.28}$$	$${768.13}$$ < $${769.38}$$	$${-0.14}$$	$${260.98}$$ < $${262.06}$$
✅	docker_agent_arm64	$${-0.28}$$	$${774.37}$$ < $${778.35}$$	$${-0.11}$$	$${250.1}$$ < $${251.72}$$
✅	docker_agent_jmx_amd64	$${-0.28}$$	$${959.01}$$ < $${960.26}$$	$${-0.16}$$	$${329.61}$$ < $${330.69}$$
✅	docker_agent_jmx_arm64	$${-0.27}$$	$${953.96}$$ < $${957.95}$$	$${-0.16}$$	$${314.7}$$ < $${316.35}$$
✅	docker_cluster_agent_amd64	$${+0}$$	$${179.41}$$ < $${179.56}$$	$${-0}$$	$${63.44}$$ < $${64.14}$$
✅	docker_cluster_agent_arm64	$${-0}$$	$${195.37}$$ < $${196.79}$$	$${+0}$$	$${59.76}$$ < $${60.69}$$
✅	docker_cws_instrumentation_amd64	$${0}$$	$${7.13}$$ < $${7.18}$$	$${-0}$$	$${2.99}$$ < $${3.33}$$
✅	docker_cws_instrumentation_arm64	$${0}$$	$${6.69}$$ < $${6.92}$$	$${-0}$$	$${2.73}$$ < $${3.09}$$
✅	docker_dogstatsd_amd64	$${0}$$	$${38.75}$$ < $${39.38}$$	$${+0}$$	$${15.0}$$ < $${15.82}$$
✅	docker_dogstatsd_arm64	$${0}$$	$${37.06}$$ < $${37.94}$$	$${-0}$$	$${14.33}$$ < $${14.83}$$
✅	dogstatsd_deb_amd64	$${0}$$	$${29.98}$$ < $${30.61}$$	$${+0}$$	$${7.93}$$ < $${8.79}$$
✅	dogstatsd_deb_arm64	$${0}$$	$${28.13}$$ < $${29.11}$$	$${+0}$$	$${6.81}$$ < $${7.71}$$
✅	dogstatsd_rpm_amd64	$${0}$$	$${29.98}$$ < $${30.61}$$	$${-0}$$	$${7.94}$$ < $${8.8}$$
✅	dogstatsd_suse_amd64	$${0}$$	$${29.98}$$ < $${30.61}$$	$${-0}$$	$${7.94}$$ < $${8.8}$$
✅	iot_agent_deb_amd64	$${0}$$	$${42.73}$$ < $${43.29}$$	$${-0}$$	$${11.19}$$ < $${12.04}$$
✅	iot_agent_deb_arm64	$${0}$$	$${39.88}$$ < $${40.92}$$	$${+0}$$	$${9.57}$$ < $${10.45}$$
✅	iot_agent_deb_armhf	$${0}$$	$${40.44}$$ < $${41.03}$$	$${+0}$$	$${9.77}$$ < $${10.62}$$
✅	iot_agent_rpm_amd64	$${0}$$	$${42.73}$$ < $${43.29}$$	$${+0}$$	$${11.21}$$ < $${12.06}$$
✅	iot_agent_suse_amd64	$${0}$$	$${42.73}$$ < $${43.29}$$	$${+0}$$	$${11.21}$$ < $${12.06}$$

[cit-pr-commenter[bot]]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 6841485c-608f-4daa-b75d-fe40041d41d9

Baseline: 64b0969334d221270a166c324f09c578df65e7ae Comparison: 9aa5389589e9ac5b0fa73bd9310a2723e3c019f4 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	+0.82	[-2.22, +3.86]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_logs	% cpu utilization	+2.65	[+1.17, +4.14]	1	Logs bounds checks dashboard
➖	docker_containers_cpu	% cpu utilization	+0.82	[-2.22, +3.86]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	+0.45	[+0.36, +0.53]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	+0.43	[+0.23, +0.64]	1	Logs bounds checks dashboard
➖	file_tree	memory utilization	+0.12	[+0.05, +0.19]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.12, +0.14]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.07, +0.08]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	+0.00	[-0.12, +0.12]	1	Logs
➖	quality_gate_idle	memory utilization	-0.02	[-0.07, +0.03]	1	Logs bounds checks dashboard
➖	file_to_blackhole_0ms_latency	egress throughput	-0.02	[-0.44, +0.40]	1	Logs
➖	otlp_ingest_metrics	memory utilization	-0.02	[-0.18, +0.14]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.02	[-0.07, +0.02]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.05	[-0.43, +0.32]	1	Logs
➖	docker_containers_memory	memory utilization	-0.07	[-0.14, +0.01]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.08	[-0.49, +0.32]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.10	[-0.13, -0.06]	1	Logs bounds checks dashboard
➖	otlp_ingest_logs	memory utilization	-0.14	[-0.23, -0.05]	1	Logs
➖	ddot_logs	memory utilization	-0.15	[-0.22, -0.09]	1	Logs
➖	ddot_metrics	memory utilization	-0.19	[-0.43, +0.06]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.29	[-0.52, -0.06]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.34	[-0.50, -0.18]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.72	[-0.78, -0.66]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.86	[-1.07, -0.65]	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:

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_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_metrics_logs, 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_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_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_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.

[pgimalac]

/merge

[dd-devflow-routing-codex[bot]]

View all feedbacks in Devflow UI.

2025-12-17 13:17:10 UTC :information_source: Start processing command /merge

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2025-12-17 13:36:15 UTC :information_source: MergeQueue: merge request added to the queue

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2025-12-17 14:46:09 UTC :information_source: MergeQueue: This merge request was merged