ECE: customize logging and metrics retention with ILM and data streams

[eedugon]

Summary

Updating the document to set retention of logging and metrics data on ECE.

Improvements:

• Introduction and flow within the ECE platform monitoring section.
• Default ILM policies names identified (per https://github.com/elastic/cloud/issues/116800)
• Procedure updated, as it wasn't completely accurate (mappings and settings were not considered) and extra steps added.
• Added information about available index templates (not a complete list, just the most popular ones).

Closes https://github.com/elastic/docs-content-internal/issues/466
Closes https://github.com/elastic/cloud/issues/116800

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

Tool(s) and model(s) used: Cursor in auto mode

[github-actions]

Vale Linting Results

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File	Line	Rule	Message
deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention.md	48	Elastic.Clone	Use Clone only when referring to cloning a GitHub repository or creating a copy that is linked to the original. Often confused with 'copy' and 'duplicate'.

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[github-actions]

🔍 Preview links for changed docs

• deploy-manage/deploy/cloud-enterprise/system-deployments-configuration.md
• deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention.md

[kunisen]

I did quick check and left some comments. Mainly about making sure the user expectation on sizing, and some tech details.

[eedugon]

@kunisen : I've made changes based on your suggestions. Really great catches.
Let me know your thoughts.

[kunisen]

Looks really great! Thanks Edu for your time effort on this! ❤️

[kilfoyle]

LGTM! ⛵
Looks great @eedugon!

If I'm not mistaken, this new page is basically an ECE-specific version of the general procedure described in Customize built-in ILM policies in Elasticsearch, so it might be helpful to mention that somewhere with a link.

[eedugon]

Thanks for the review and improvements suggestions @davidkyle , all of them are more than welcome!

If I'm not mistaken, this new page is basically an ECE-specific version of the general procedure described in Customize built-in ILM policies in Elasticsearch, so it might be helpful to mention that somewhere with a link.

I didn't know it, thanks! I'll find the way to add it as a reference.

I finally didn't include anything about component templates and @custom examples because we are not following that path, but maybe in the future we will, if ECE managed templates provide and support them.