[AGENTRUN-115] Get the hostname from running agent if possible in hostname command

[pgimalac]

What does this PR do?

Change the hostname subcommand to try reaching out to the running agent before falling back to local computation of the hostname.

Motivation

The command should give the same hostname as the running agent, in case of transient error (eg. network) it is currently not the case.
Reaching out to the running agent is a more correct behavior, and in the worst case we fallback to the local computation and print a warning.
This should help avoid some issues we've seen in support cases and flaky end-to-end tests.

Describe how you validated your changes

Local testing:

$ DD_HOSTNAME=myname ./bin/agent/agent hostname
COMP-VWFVT21J6N
$ DD_HOSTNAME=myname ./bin/agent/agent hostname --local
myname

Also added unit tests to ensure the behavior is correct.

Possible Drawbacks / Trade-offs

Additional Notes

[louis-cqrl]

LGTM overall

[agent-platform-auto-pr]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv aws.create-vm --pipeline-id=56918380 --os-family=ubuntu

Note: This applies to commit 755c8d4

[agent-platform-auto-pr]

Uncompressed package size comparison

Comparison with ancestor 526645bb889d540d8ce7a39fb6cc932b8ea58ca6

Diff per package

package	diff	status	size	ancestor	threshold
datadog-agent-x86_64-rpm	0.04MB	⚠️	849.88MB	849.83MB	0.50MB
datadog-agent-x86_64-suse	0.04MB	⚠️	849.88MB	849.83MB	0.50MB
datadog-agent-aarch64-rpm	0.03MB	⚠️	839.95MB	839.92MB	0.50MB
datadog-agent-amd64-deb	0.02MB	⚠️	840.08MB	840.07MB	0.50MB
datadog-heroku-agent-amd64-deb	0.01MB	⚠️	443.29MB	443.28MB	0.50MB
datadog-agent-arm64-deb	0.01MB	⚠️	830.17MB	830.17MB	0.50MB
datadog-iot-agent-arm64-deb	0.00MB	✅	59.27MB	59.26MB	0.50MB
datadog-iot-agent-aarch64-rpm	0.00MB	✅	59.33MB	59.33MB	0.50MB
datadog-dogstatsd-amd64-deb	0.00MB	✅	39.42MB	39.42MB	0.50MB
datadog-dogstatsd-x86_64-rpm	0.00MB	✅	39.50MB	39.50MB	0.50MB
datadog-dogstatsd-x86_64-suse	0.00MB	✅	39.50MB	39.50MB	0.50MB
datadog-dogstatsd-arm64-deb	0.00MB	✅	37.96MB	37.96MB	0.50MB
datadog-iot-agent-amd64-deb	0.00MB	✅	62.02MB	62.02MB	0.50MB
datadog-iot-agent-x86_64-rpm	0.00MB	✅	62.09MB	62.09MB	0.50MB
datadog-iot-agent-x86_64-suse	0.00MB	✅	62.09MB	62.09MB	0.50MB

Decision

⚠️ Warning

[agent-platform-auto-pr]

Static quality checks ✅

Please find below the results from static quality gates

Successful checks

Info

Result	Quality gate	On disk size	On disk size limit	On wire size	On wire size limit
✅	static_quality_gate_agent_deb_amd64	812.9MiB	847.49MiB	196.88MiB	212.33MiB
✅	static_quality_gate_agent_deb_arm64	803.52MiB	836.66MiB	178.09MiB	192.5MiB
✅	static_quality_gate_agent_rpm_amd64	812.87MiB	847.82MiB	199.31MiB	215.76MiB
✅	static_quality_gate_agent_rpm_arm64	803.4MiB	836.66MiB	180.85MiB	194.24MiB
✅	static_quality_gate_agent_suse_amd64	812.87MiB	847.82MiB	199.31MiB	215.76MiB
✅	static_quality_gate_agent_suse_arm64	803.48MiB	836.66MiB	180.85MiB	194.24MiB
✅	static_quality_gate_dogstatsd_deb_amd64	37.67MiB	49.7MiB	9.78MiB	20.6MiB
✅	static_quality_gate_dogstatsd_deb_arm64	36.27MiB	48.1MiB	8.49MiB	19.1MiB
✅	static_quality_gate_dogstatsd_rpm_amd64	37.67MiB	49.7MiB	9.79MiB	20.6MiB
✅	static_quality_gate_dogstatsd_suse_amd64	37.67MiB	49.7MiB	9.79MiB	20.6MiB
✅	static_quality_gate_iot_agent_deb_amd64	59.23MiB	69.0MiB	14.88MiB	24.8MiB
✅	static_quality_gate_iot_agent_deb_arm64	56.59MiB	66.4MiB	12.82MiB	22.8MiB
✅	static_quality_gate_iot_agent_rpm_amd64	59.23MiB	69.0MiB	14.9MiB	24.8MiB
✅	static_quality_gate_iot_agent_rpm_arm64	56.6MiB	66.4MiB	12.85MiB	22.8MiB
✅	static_quality_gate_iot_agent_suse_amd64	59.23MiB	69.0MiB	14.9MiB	24.8MiB
✅	static_quality_gate_docker_agent_amd64	897.31MiB	931.7MiB	300.93MiB	318.67MiB
✅	static_quality_gate_docker_agent_arm64	911.12MiB	944.08MiB	286.42MiB	303.0MiB
✅	static_quality_gate_docker_agent_jmx_amd64	1.07GiB	1.1GiB	376.01MiB	393.75MiB
✅	static_quality_gate_docker_agent_jmx_arm64	1.07GiB	1.1GiB	357.5MiB	373.71MiB
✅	static_quality_gate_docker_dogstatsd_amd64	45.81MiB	57.88MiB	17.28MiB	28.29MiB
✅	static_quality_gate_docker_dogstatsd_arm64	44.45MiB	56.27MiB	16.16MiB	27.06MiB
✅	static_quality_gate_docker_cluster_agent_amd64	264.94MiB	274.78MiB	106.35MiB	116.28MiB
✅	static_quality_gate_docker_cluster_agent_arm64	280.92MiB	290.82MiB	101.18MiB	111.12MiB

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: a9a4d6ea-64f0-40e5-98fd-5a6b16e0ea3b

Baseline: 526645b
Comparison: 755c8d4
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_logs	% cpu utilization	+0.83	[-2.10, +3.75]	1	Logs
➖	file_tree	memory utilization	+0.74	[+0.69, +0.79]	1	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.43	[-0.52, +1.38]	1	Logs
➖	quality_gate_idle	memory utilization	+0.43	[+0.39, +0.46]	1	Logs bounds checks dashboard
➖	tcp_syslog_to_blackhole	ingress throughput	+0.30	[+0.23, +0.36]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.24	[-0.54, +1.02]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.29, +0.31]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.01	[-0.66, +0.68]	1	Logs
➖	file_to_blackhole_0ms_latency_http2	egress throughput	+0.01	[-0.86, +0.88]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	+0.00	[-0.85, +0.86]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	+0.00	[-0.63, +0.63]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.02, +0.02]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.02	[-0.80, +0.77]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.02	[-0.82, +0.78]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.07	[-0.12, -0.02]	1	Logs bounds checks dashboard
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.10	[-0.57, +0.37]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http1	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http1	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http2	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http2	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency_linear_load	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_300ms_latency	lost_bytes	10/10
✅	file_to_blackhole_300ms_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
✅	quality_gate_logs	lost_bytes	10/10
✅	quality_gate_logs	memory_usage	10/10

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 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 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_logs, 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 memory_usage: 10/10 replicas passed. Gate passed.

[maycmlee]

Couple of small edits, but approving to not block merge.

[dustmop]

LGTM, with one small nit

[dustmop]

Very minor nit: the vars hname and err aren't used outside of this if block. You can change this to hname, err := instead of having the variables declared above.