[DBMON-6669] Fix resolve_db_host for IPv6 loopback addresses

[eric-weaver]

What does this PR do?

Fixes resolve_db_host in datadog-checks-base so loopback database endpoints use the agent hostname for metrics instead of the raw IP literal.

• Adds _try_parse_db_host_ip to parse IPv4/IPv6 address literals (bracketed IPv6, zone-scoped IPv6 via IPv6Interface).
• Adds _is_local_db_host to detect localhost, unix sockets, and loopback IPs (127.0.0.1, ::1, [::1], etc.).
• When the DB host is local, returns datadog_agent.get_hostname() before gethostbyname, restoring correct host tags and datadog.yaml host-level tags on MySQL/Postgres/SQL Server metrics.
• Expands and reorders test_resolve_db_host cases.

Motivation

Fixes DataDog/datadog-agent#51280: on Agent 7.79.0, MySQL metrics lost datadog.yaml host tags and used host:::1 when server was set to ::1. Agent 7.78.4 was unaffected.

Agent 7.79.0 bundles datadog-checks-base 37.35.x, which includes #23181: when gethostbyname fails, resolve_db_host returns the configured db_host rather than the agent hostname. That is correct for remote hostnames that fail DNS lookup, but loopback IP literals (e.g. ::1) also fail gethostbyname because it is IPv4-only—they must not be treated as DNS failures. This PR classifies loopback addresses as local before any name resolution, so we keep #23181’s semantics for genuinely unresolvable remote hosts while restoring the agent hostname for on-host database connections.

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

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 80c7783c9f

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[datadog-official]

   

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 5 Pipeline jobs failed

PR All | test / j06ca546 / SNMP     

🔄 Retry job. This looks flaky and may succeed on retry.

Failed to resolve 'ddintegrations.blob.core.windows.net' during SNMP request due to NameResolutionError.

PR All | test / j46da136 / JBoss_WildFly     

🔄 Retry job. This looks flaky and may succeed on retry.

Could not resolve: ddintegrations.blob.core.windows.net:443

PR All | test / j5a9585a / IBM ACE     

🔄 Retry job. This looks flaky and may succeed on retry.

Could not resolve host: ddintegrations.blob.core.windows.net, leading to failure in retrieving necessary files.

View all 5 failed jobs.

🧪 20 Tests failed in 1 job

PR All | run  

test_bulk_table from test_check.py   (Fix with Cursor)

HTTPSConnectionPool(host='ddintegrations.blob.core.windows.net', port=443): Max retries exceeded with url: /snmp/cisco-3850.snmprec (Caused by NameResolutionError("HTTPSConnection(host='ddintegrations.blob.core.windows.net', port=443): Failed to resolve 'ddintegrations.blob.core.windows.net' ([Errno -2] Name or service not known)"))

test_cast_metrics from test_check.py   (Fix with Cursor)

HTTPSConnectionPool(host='ddintegrations.blob.core.windows.net', port=443): Max retries exceeded with url: /snmp/cisco-3850.snmprec (Caused by NameResolutionError("HTTPSConnection(host='ddintegrations.blob.core.windows.net', port=443): Failed to resolve 'ddintegrations.blob.core.windows.net' ([Errno -2] Name or service not known)"))

View all 20 test failures

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 87.55% (+0.13%)

Useful? React with 👍 / 👎

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 93c483d | Docs | Datadog PR Page | Give us feedback!}

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.95%. Comparing base (b5362c7) to head (9badf28).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[AAraKKe]

Hi @eric-weaver, this review was generated with Claude Code and has been looked over and approved before posting. I believe the comments below are valid — feel free to discuss any you disagree with.

Comment legend

praise: no action needed, just celebrate!
note: informational, no action required.
question: seeking clarification or understanding your approach.
nit: minor, non-blocking (style, typo). Feel free to ignore.
suggestion: optional improvement, recommended but not required.
request: a change I believe is necessary before merging.

[AAraKKe]

Question: Is there a reason to route zone-scoped addresses through IPv6Interface(host).ip rather than ip_address(host) directly? In Python 3.9+, ip_address("fe80::1%eth0") returns an IPv6Address with scope_id set, and is_loopback works correctly on the result. IPv6Interface is semantically for CIDR network addresses and defaults to /128 when no prefix is given, so the detour works but is unusual. If this is a holdover from earlier Python compatibility, the pyproject.toml for datadog-checks-base targets 3.13 — ip_address for both branches would be a small simplification.

[eric-weaver]

Agree this simplifies it. Made the change

Review from sethsamuel is dismissed. Related teams and files:

• database-monitoring-agent
  • datadog_checks_base/datadog_checks/base/utils/db/utils.py
  • datadog_checks_base/tests/base/utils/db/test_util.py

Review from Kyle-Neale is dismissed. Related teams and files:

• agent-integrations
  • datadog_checks_base/datadog_checks/base/utils/db/utils.py
  • datadog_checks_base/tests/base/utils/db/test_util.py

Review from AAraKKe is dismissed. Related teams and files:

• agent-integrations
  • datadog_checks_base/datadog_checks/base/utils/db/utils.py
  • datadog_checks_base/tests/base/utils/db/test_util.py

[dd-octo-sts]

Validation Report

All 21 validations passed.

Show details

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	✅

View full run