gearmand: add container-based config discovery support

[vitkyrka]

What does this PR do?

Adds container-based config discovery support to gearmand.

• Port selection rationale: Port 4730 is gearmand's well-known default job-server port, documented in the Gearman protocol spec. This check pulls stats from the same port.

• Endpoint: gearmand's admin protocol is raw TCP (not HTTP), and the check's config uses separate server/port fields rather than a URL field, so spec.yaml uses the manual from_ports strategy form (candidates: - server: ..., port: ...) instead of the discovery/openmetrics_from_ports template.

• Standard image: there's no single "official" Docker Hub image for gearmand, but several actively used, vendor-published community images all share the same short name gearmand (e.g. artefactual/gearmand, used by the Archivematica project and also used by this integration's own test fixture; dockage/gearmand; appscode/gearmand).

• Exact-tag-match test helper: the existing test_e2e's assertions (assert_metrics() in tests/test_integration_e2e.py) use assert_metric/assert_service_check with a fixed tags= list, which does exact tag-set matching. Discovery can't reproduce that same tag set — the server tag reflects the discovered container's own docker-network address rather than common.HOST, no tags config field is set (discovery has no way to derive it), and Autodiscovery injects its own container tags (docker_image, image_id, ...) on top, so we drop the tag assertion.

• Compose service name mismatch: the compose file's service is named gearman (see tests/compose/docker-compose.yaml), not gearmand, so test_e2e_discovery_all_candidates passes compose_service='gearman' explicitly — the helper's default fallback resolves to the integration's own package name (gearmand), which wouldn't match.

Motivation

https://datadoghq.atlassian.net/browse/DSCVR-552

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add qa/required if this PR needs QA validation, or qa/skip-qa if it does not. Exactly one of the two is required.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[datadog-official]

 

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 66.67%
• Overall Coverage: 76.33% (-12.04%)

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

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• gearmand: add container-based config discovery support #24487 👈 (View in Graphite)
• Propagate docker_run env vars to discovery-stability check's compose command #24533 : 2 other dependent PRs (#24479 , #24494 )
• master

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[dd-octo-sts]

Validation Report

All 21 validations passed.

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Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and code coverage settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
qa-label	Validate the pull request declares whether it needs QA for the next Agent release	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

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