elastic/elasticsearch

Add columns CAT Shards for _tier_preference and node.roles

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#136895 opened on Oct 21, 2025

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:Core/Infra/CAT APIs>enhancementTeam:Core/Infragood first issue

Description

Description

👋 howdy!

Hopefully this avoids the XPack-vs-commercial issues surfaced in https://github.com/elastic/elasticsearch/issues/37499. (XY Problem:) I'd like to streamline investigating assigned shard allocation issues related to ILM. As part of flow after https://github.com/elastic/elasticsearch/pull/99612 or Health Report telling you indices are flagged stagnant on migrations.

As part of this, I'd like if CAT Shards would report columns

In practice, I usually flag via an aggregated view and then review a table of what'd be the above similar output. For example when cold backs up warm backs up hot:

TIA!

Contributor guide

Tech stack
java
Domain
backendapi
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Familiarity with Elasticsearch CAT APIBasic knowledge of Java and Elasticsearch codebase
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The issue requests adding two columns (tier preference and node.roles) to the CAT shards API response. Look at the CAT shards action implementation, likely in the 'cat' module. The response format is defined in a class like RestCatShardsAction or similar. Adding columns requires updating the response builder and possibly the parsing logic. Check existing columns for reference. There is a linked issue #37499 for context on XPack vs commercial nuances. No open PRs; this is a good first task for understanding CAT API internals.