[8.19](backport #47565) libbeat/processors/cache: improve logging and add ignore failure option

[mergify]

Proposed commit message

See title.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

To see the new behaviours, run

$ go test -v -run TestCache/get_missing_value             
=== RUN   TestCache
=== RUN   TestCache/get_missing_value
    logger.go:146: 2025-11-11T13:52:13.671+1030	INFO	cache	initialized cache processor	{"instance_id": 1, "details": "cache=[operation=get, store_id=memory:aidmaster, key_field=crowdstrike.aid, target_field=crowdstrike.metadata_new, ignore_missing=true, ignore_failure=false, overwrite_fields=false]"}
    cache_test.go:662: cache=[operation=get, store_id=memory:aidmaster, key_field=crowdstrike.aid, target_field=crowdstrike.metadata_new, ignore_missing=true, ignore_failure=false, overwrite_fields=false]
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	get	{"instance_id": 1, "backend_id": "memory:aidmaster", "config": {"Key":"crowdstrike.aid","Target":"crowdstrike.metadata_new"}}
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	get	{"instance_id": 1, "backend_id": "memory:aidmaster", "key": "one"}
=== RUN   TestCache/get_missing_value_ignore_error
    logger.go:146: 2025-11-11T13:52:13.672+1030	INFO	cache	initialized cache processor	{"instance_id": 2, "details": "cache=[operation=get, store_id=memory:aidmaster, key_field=crowdstrike.aid, target_field=crowdstrike.metadata_new, ignore_missing=true, ignore_failure=true, overwrite_fields=false]"}
    cache_test.go:662: cache=[operation=get, store_id=memory:aidmaster, key_field=crowdstrike.aid, target_field=crowdstrike.metadata_new, ignore_missing=true, ignore_failure=true, overwrite_fields=false]
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	get	{"instance_id": 2, "backend_id": "memory:aidmaster", "config": {"Key":"crowdstrike.aid","Target":"crowdstrike.metadata_new"}}
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	get	{"instance_id": 2, "backend_id": "memory:aidmaster", "key": "one"}
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	ignoring get error	{"instance_id": 2, "backend_id": "memory:aidmaster", "error": "metadata not found for 'one' in memory:aidmaster: metadata not found"}
    logger.go:146: 2025-11-11T13:52:13.672+1030	DEBUG	cache	no match	{"instance_id": 2, "backend_id": "memory:aidmaster", "error": "field in key_field not found in the event"}
--- PASS: TestCache (0.00s)
    --- PASS: TestCache/get_missing_value (0.00s)
    --- PASS: TestCache/get_missing_value_ignore_error (0.00s)
PASS

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Logs

---

This is an automatic backport of pull request #47565 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 637949b has failed:

On branch mergify/bp/8.19/pr-47565
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit 637949be4.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   changelog/fragments/1762831091-s6615-cache.yaml
	modified:   libbeat/processors/cache/cache.go
	modified:   libbeat/processors/cache/cache_test.go
	modified:   libbeat/processors/cache/config.go
	modified:   libbeat/processors/cache/docs/cache.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/reference/filebeat/add-cached-metadata.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[vishaangelova]

Docs LGTM!

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.19/pr-47565 upstream/mergify/bp/8.19/pr-47565
git merge upstream/8.19
git push upstream mergify/bp/8.19/pr-47565

[mergify]

This pull request has not been merged yet. Could you please review and merge it @efd6? 🙏

[efd6]

/test

[mergify]

This pull request has not been merged yet. Could you please review and merge it @efd6? 🙏

[efd6]

/test

[mergify]

This pull request has not been merged yet. Could you please review and merge it @efd6? 🙏

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.19/pr-47565 upstream/mergify/bp/8.19/pr-47565
git merge upstream/8.19
git push upstream mergify/bp/8.19/pr-47565