[AGTMETRICS-393] Prevent DSD server from starting when data plane is enabled and handling DSD.

[tobz]

What does this PR do?

Ensures that the DogStatsD server in the Core Agent does not run when Agent Data Plane is enabled and serving DSD traffic.

Motivation

Only one process can be handling DSD at a time, so this code is a strengthening of that invariant which we have been achieving, to date, by setting the appropriate environment variables for the respective processes. Doing so technically works, but is fragile and better handled directly in the Core Agent.

As part of doing this, we've introduced a new wrapper type for basic DSD configuration which currently only contains the logic around if DSD is enabled at all, and where it's enabled. This lets us centralize the logic as we depend on it in a few different places throughout the codebase. Our logic now considers the notion of DogStatsD being enabled at all -- like, does the customer want DSD to be running, regardless of how we actually make that happen? -- and then separately can figure out where it's enabled.

Additionally, we now skip displaying the DogStatsD section in the agent status output when DSD is disabled internally, as the metrics will always be zero and ADP will be pushing its status data to RAR and will effectively take over in terms of providing DSD status.

Describe how you validated your changes

Built and ran the Agent locally, with a few different variations of config settings:

• all defaults: DSD runs in Core Agent, Core Agent-specific DSD section present in status output
• use_dogstatsd -> false: DSD does not run in Core Agent, Core Agent-specific DSD section not present in status output
• data_plane.enabled/data_plane.dogstatsd.enabled -> true: DSD does not run in Core Agent, Core Agent-specific DSD section not present in status output
• use_dogstatsd -> false, data_plane.enabled/data_plane.dogstatsd.enabled -> true: DSD does not run in Core Agent, Core Agent-specific DSD section not present in status output

Additionally, we've added new unit tests (and updated some existing ones) to ensure the logic is obeyed in terms of when DSD should and should not be running in the Core Agent.

Additional Notes

[agent-platform-auto-pr]

Go Package Import Differences

Baseline: 12bfa8a
Comparison: ad12a81

binary	os	arch	change
agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
agent	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
agent	windows	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
agent	darwin	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
agent	darwin	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
iot-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
iot-agent	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
heroku-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
cluster-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
cluster-agent	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
cluster-agent-cloudfoundry	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
cluster-agent-cloudfoundry	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
dogstatsd	linux	amd64	+2, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config +github.com/DataDog/datadog-agent/comp/dogstatsd/status/statusimpl
dogstatsd	linux	arm64	+2, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config +github.com/DataDog/datadog-agent/comp/dogstatsd/status/statusimpl
trace-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
trace-agent	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
trace-agent	windows	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
trace-agent	darwin	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
trace-agent	darwin	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
heroku-trace-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
otel-agent	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
otel-agent	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
full-host-profiler	linux	amd64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config
full-host-profiler	linux	arm64	+1, -0 +github.com/DataDog/datadog-agent/comp/dogstatsd/config

[agent-platform-auto-pr]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 12bfa8a

Successful checks

Info

	Quality gate	Delta	On disk size (MiB)	Delta	On wire size (MiB)
✅	agent_deb_amd64	$${+0}$$	$${705.25}$$ < $${706.32}$$	$${+0.03}$$	$${172.94}$$ < $${173.81}$$
✅	agent_deb_amd64_fips	$${+0}$$	$${700.09}$$ < $${701.16}$$	$${+0.05}$$	$${171.71}$$ < $${172.71}$$
✅	agent_heroku_amd64	$${+0}$$	$${327.43}$$ < $${327.69}$$	$${+0}$$	$${87.37}$$ < $${88.19}$$
✅	agent_msi	$${+0.01}$$	$${978.71}$$ < $${982.08}$$	$${-0.03}$$	$${141.79}$$ < $${143.01}$$
✅	agent_rpm_amd64	$${+0}$$	$${705.24}$$ < $${706.31}$$	$${+0.01}$$	$${175.95}$$ < $${176.86}$$
✅	agent_rpm_amd64_fips	$${+0}$$	$${700.07}$$ < $${701.15}$$	$${-0.01}$$	$${174.0}$$ < $${174.95}$$
✅	agent_rpm_arm64	$${+0.01}$$	$${690.92}$$ < $${691.67}$$	$${+0.03}$$	$${159.79}$$ < $${160.7}$$
✅	agent_rpm_arm64_fips	$${-0}$$	$${686.72}$$ < $${687.54}$$	$${+0}$$	$${159.12}$$ < $${160.1}$$
✅	agent_suse_amd64	$${+0}$$	$${705.24}$$ < $${706.31}$$	$${+0.01}$$	$${175.95}$$ < $${176.86}$$
✅	agent_suse_amd64_fips	$${+0}$$	$${700.07}$$ < $${701.15}$$	$${-0.01}$$	$${174.0}$$ < $${174.95}$$
✅	agent_suse_arm64	$${+0.01}$$	$${690.92}$$ < $${691.67}$$	$${+0.03}$$	$${159.79}$$ < $${160.7}$$
✅	agent_suse_arm64_fips	$${-0}$$	$${686.72}$$ < $${687.54}$$	$${+0}$$	$${159.12}$$ < $${160.1}$$
✅	docker_agent_amd64	$${+0}$$	$${767.58}$$ < $${768.66}$$	$${-0}$$	$${260.64}$$ < $${261.52}$$
✅	docker_agent_arm64	$${+0.01}$$	$${777.53}$$ < $${778.35}$$	$${-0.01}$$	$${250.81}$$ < $${251.72}$$
✅	docker_agent_jmx_amd64	$${+0}$$	$${958.45}$$ < $${959.54}$$	$${-0}$$	$${329.27}$$ < $${330.15}$$
✅	docker_agent_jmx_arm64	$${+0.01}$$	$${957.13}$$ < $${957.95}$$	$${+0}$$	$${315.43}$$ < $${316.35}$$
✅	docker_cluster_agent_amd64	$${0}$$	$${178.88}$$ < $${179.28}$$	$${+0}$$	$${63.18}$$ < $${63.96}$$
✅	docker_cluster_agent_arm64	$${0}$$	$${196.39}$$ < $${196.79}$$	$${+0}$$	$${59.89}$$ < $${60.69}$$
✅	docker_cws_instrumentation_amd64	$${0}$$	$${7.07}$$ < $${7.12}$$	$${+0}$$	$${2.95}$$ < $${3.29}$$
✅	docker_cws_instrumentation_arm64	$${0}$$	$${6.69}$$ < $${6.92}$$	$${+0}$$	$${2.7}$$ < $${3.07}$$
✅	docker_dogstatsd_amd64	$${+0}$$	$${38.6}$$ < $${39.3}$$	$${+0}$$	$${14.91}$$ < $${15.76}$$
✅	docker_dogstatsd_arm64	$${+0.06}$$	$${37.3}$$ < $${37.94}$$	$${+0}$$	$${14.36}$$ < $${14.83}$$
✅	dogstatsd_deb_amd64	$${+0}$$	$${29.82}$$ < $${30.53}$$	$${+0}$$	$${7.87}$$ < $${8.75}$$
✅	dogstatsd_deb_arm64	$${+0}$$	$${28.34}$$ < $${29.11}$$	$${-0}$$	$${6.8}$$ < $${7.71}$$
✅	dogstatsd_rpm_amd64	$${+0}$$	$${29.82}$$ < $${30.53}$$	$${+0}$$	$${7.88}$$ < $${8.76}$$
✅	dogstatsd_suse_amd64	$${+0}$$	$${29.82}$$ < $${30.53}$$	$${+0}$$	$${7.88}$$ < $${8.76}$$
✅	iot_agent_deb_amd64	$${+0}$$	$${42.6}$$ < $${43.19}$$	$${+0}$$	$${11.12}$$ < $${11.98}$$
✅	iot_agent_deb_arm64	$${+0}$$	$${40.34}$$ < $${40.92}$$	$${-0}$$	$${9.58}$$ < $${10.45}$$
✅	iot_agent_deb_armhf	$${+0}$$	$${40.24}$$ < $${40.86}$$	$${+0}$$	$${9.69}$$ < $${10.56}$$
✅	iot_agent_rpm_amd64	$${+0}$$	$${42.6}$$ < $${43.19}$$	$${-0}$$	$${11.14}$$ < $${12.0}$$
✅	iot_agent_suse_amd64	$${+0}$$	$${42.6}$$ < $${43.19}$$	$${-0}$$	$${11.14}$$ < $${12.0}$$

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 0b7ee236-70de-470e-b1d0-de89194c4cf3

Baseline: 12bfa8a
Comparison: ad12a81
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	+1.49	[-1.49, +4.48]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	docker_containers_cpu	% cpu utilization	+1.49	[-1.49, +4.48]	1	Logs
➖	otlp_ingest_logs	memory utilization	+0.58	[+0.49, +0.68]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	+0.41	[+0.21, +0.61]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	+0.32	[+0.12, +0.53]	1	Logs bounds checks dashboard
➖	ddot_metrics	memory utilization	+0.30	[+0.07, +0.54]	1	Logs
➖	docker_containers_memory	memory utilization	+0.13	[+0.04, +0.21]	1	Logs
➖	file_tree	memory utilization	+0.11	[+0.06, +0.16]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.02	[-0.36, +0.39]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.02	[-0.13, +0.16]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.08, +0.09]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	+0.00	[-0.12, +0.13]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.01	[-0.43, +0.41]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.03	[-0.42, +0.35]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.04	[-0.09, +0.02]	1	Logs
➖	otlp_ingest_metrics	memory utilization	-0.08	[-0.23, +0.07]	1	Logs
➖	quality_gate_idle	memory utilization	-0.11	[-0.16, -0.06]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.12	[-0.17, -0.07]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.13	[-0.37, +0.10]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.25	[-0.40, -0.09]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.27	[-0.32, -0.22]	1	Logs bounds checks dashboard
➖	ddot_logs	memory utilization	-0.44	[-0.50, -0.38]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.52	[-0.60, -0.44]	1	Logs
➖	quality_gate_logs	% cpu utilization	-2.31	[-3.73, -0.88]	1	Logs bounds checks dashboard

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_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_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_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 cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.