opensearch-project/OpenSearch

[Feature Request] Paginate snapshot indices status fetching

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#16,985 opened on Jan 9, 2025

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 (19 comments) (0 reactions) (1 assignee)Java (8,123 stars) (1,505 forks)batch import
Storage:Snapshotsenhancementgood first issue

Description

Is your feature request related to a problem? Please describe

Our customers depend on the snapshot status API to access information about snapshot indices, like store size, number of docs, etc. The TransportSnapshotStatusAction utilizes a single Generic thread to retrieve repository data, snapshot information, snapshot index metadata, and shard snapshot status if the specified snapshot(s) is not currently running. However, when the specified snapshot contains a large number of indices, the execution time for this action becomes significantly prolonged.

In one of the snapshot which has 15000+ shards, snapshot status fetching was taking 8min.

Describe the solution you'd like

Provide a new API (_snapshot/{repository}/{snapshot}/_list/indices) to paginate snapshot indices status like we did in #14258. The new API works only for indexes belonging to a specific snapshot. Since the order of indices in SnapshotInfo is settled, we can simply use from + size to paginate. If the specified snapshot is running, then the paginating parameters will have no effect.

Related component

Storage:Snapshots

Describe alternatives you've considered

Using the snapshot thread pool to parallelize indices snapshot status fetching. But the snapshot thread pool might be blocked on long running tasks. Moreover, the maximum number of threads in the snapshot thread pool is only 5, so the speedup effect may be limited

Additional context

No response

Contributor guide

Tech stack
javarest api
Domain
backendapiperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with OpenSearch snapshotsJava development experienceKnowledge of pagination patterns
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Examine the existing TransportSnapshotStatusAction class to understand current snapshot status fetching logic, particularly how index metadata is retrieved. Review the implementation in #14258 for paginating snapshot indices list as a reference. Investigate SnapshotInfo's indices ordering and determine how to add from+size parameters. Ensure the new API works different than the status API for running snapshots as specified in the issue.