[ECE] Document component template method to customize logging-and-metrics retention

[eedugon]

Summary

• Documents the new component template method to customize data retention in the ECE logging-and-metrics cluster, available from ECE 4.1.1 (applies_to set to 4.2 to avoid confusion in 4.1.0).
• Adds a table of reserved @custom component template names with their scope (index-specific, all logs, all metrics, all data streams).
• Renames the existing cloning method section and adds a note directing ECE 4.1.1+ users to the new approach.
• Updates the page intro to describe the overall process and differentiate by version.

Related

Closes https://github.com/elastic/docs-content-internal/issues/840

Test plan

• Preview builds correctly and the new section renders with the ga 4.2+ badge.
• Links to ILM policy, component templates, and data stream rollover docs resolve correctly.
• applies_to block on the new section displays the correct version badge.

🤖 Generated with Claude Code

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🔍 Preview links for changed docs

• deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention.md

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Elastic Docs Style Checker (Vale)

Summary: 2 suggestions found

💡 Suggestions (2): Optional style improvements. Apply when helpful.

File	Line	Rule	Message
deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention.md	90	Elastic.Clone	Use cloning only when referring to cloning a GitHub repository or creating a copy that is linked to the original. Often confused with 'copy' and 'duplicate'.
deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention.md	100	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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[gigerdo]

LGTM, thank you for adding more docs on this 👍

[shainaraskas]

general lgtm, with some suggestions to consider

[shainaraskas]

if you expand the link target it will be clearer that you're linking down to a procedure specific to the retention period, rather than a definition of / more information on component templates generically

Suggested change

To customize the retention period, create a new {{ilm-init}} policy with the required settings and apply it to the target data streams. On ECE 4.1.1 or later, apply it through a [component template](#customize-retention-component-templates), which is the recommended approach. On earlier versions, you can [clone the relevant index template](#customize-retention-index-templates) and configure it to use your custom {{ilm-init}} policy, though this requires repeating the procedure after upgrades that change template names.

To customize the retention period, create a new {{ilm-init}} policy with the required settings and apply it to the target data streams. On ECE 4.1.1 or later, [apply it through a component template](#customize-retention-component-templates), which is the recommended approach. On earlier versions, you can [clone the relevant index template](#customize-retention-index-templates) and configure it to use your custom {{ilm-init}} policy, though this requires repeating the procedure after upgrades that change template names.

[shainaraskas]

I think that having 4.2 and 4.1.1 here is not ideal

would prefer either

• no version in body, stay with 4.2 applicability
• 4.1 applicability, specify 4.1 in body

current version makes one seem wrong, rather than looking like we're adding precision by specifying a patch

---

re: the content, can we make the benefit statement a little punchier? right now it reads as implementation details

maybe

Suggested change

	```{applies_to}
	deployment:
	ece: ga 4.2+
	```
	Starting from ECE 4.1.1, each index template in the `logging-and-metrics` cluster includes a `composed_of` array that references a set of reserved component template names. If you create a component template with one of these names, {{es}} merges its settings into new backing indices automatically. Because these names do not include a version tag, the customization persists across ECE upgrades without any additional action.
	```{applies_to}
	deployment:
	ece: ga 4.1+
	```
	Create a component template with a reserved name to apply custom retention that remains in place after ECE upgrades.
	Each index template in the `logging-and-metrics` cluster includes a `composed_of` array that references these reserved names. If you create a matching component template, {{es}} merges its settings into new backing indices. The names do not include a version tag, so they continue to match after an ECE upgrade.
	```{note}
	This functionality is only available in ECE 4.1.1 and higher.
	```

[shainaraskas]

I assume you can define as many as you want, right? this reads as you can only define one, but maybe a couple can coexist?

Suggested change

	The following component template names are reserved for customization. Define only the one that matches the scope you need:
	The following component template names are reserved for customization. Define only the templates that match the scope you need: