Expand "Rejected requests" documentation

[rodrigomadalozzo]

https://www.elastic.co/docs/troubleshoot/elasticsearch/rejected-requests

1 - Under Check rejected tasks, added sample JSON outputs so users can better interpret the results.

Also added

The queue and active pools are point-in-time values. rejected and completed are cumulative counters on each node that reset when the node process restarts. Therefore, avoid interpreting a single snapshot “rejected/completed ratio” in isolation — compare deltas over a time window (e.g., sample every 1–5 minutes and calculate the increase in rejected vs the increase in completed). Sustained non-zero rejected deltas indicate ongoing request drops (typically surfaced to clients as HTTP 429).

Also, erring is unclear wording to me, so recommended rephrasing to something unambiguous or omit that word.

2 - Under Prevent rejected requests added

Fix indexing/search request bursts and concurrency (HTTP 429)

Rejections (HTTP 429) typically indicate the cluster is receiving work faster than it can execute (for example, during traffic bursts or when indexing/search requests are not optimized). Prevent them by shaping workload—use client-side backoff/throttling for bursts and tune request patterns (bulk sizing, concurrency, query cost) to match the cluster’s sustained throughput.

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

• Yes
• No

@stefnestor

[github-actions]

Vale Linting Results

Summary: 7 suggestions found

💡 Suggestions (7)

File	Line	Rule	Message
troubleshoot/elasticsearch/rejected-requests.md	33	Elastic.EmDashes	Don't put a space before or after a dash.
troubleshoot/elasticsearch/rejected-requests.md	35	Elastic.WordChoice	Consider using 'refer to (if it's a document), view (if it's a UI element)' instead of 'See', unless the term is in the UI.
troubleshoot/elasticsearch/rejected-requests.md	43	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
troubleshoot/elasticsearch/rejected-requests.md	43	Elastic.Semicolons	Use semicolons judiciously.
troubleshoot/elasticsearch/rejected-requests.md	45	Elastic.EmDashes	Don't put a space before or after a dash.
troubleshoot/elasticsearch/rejected-requests.md	50	Elastic.WordChoice	Consider using 'refer to (if it's a document), view (if it's a UI element)' instead of 'see', unless the term is in the UI.
troubleshoot/elasticsearch/rejected-requests.md	96	Elastic.WordChoice	Consider using 'run, start' instead of 'execute', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• troubleshoot/elasticsearch/rejected-requests.md

[kilfoyle]

Suggested change

The `queue` and `active` pools are point-in-time values. `rejected` and `completed` are cumulative counters on each node that reset when the node process restarts. Therefore, avoid interpreting a single snapshot “rejected/completed ratio” in isolation — compare deltas over a time window (e.g., sample every 1–5 minutes and calculate the increase in `rejected` vs the increase in `completed`). Sustained non-zero `rejected` deltas indicate ongoing request drops (typically surfaced to clients as HTTP 429).

The `queue` and `active` pools are point-in-time values. `rejected` and `completed` are cumulative counters on each node that reset when the node process restarts. Therefore, avoid interpreting a single snapshot “rejected/completed ratio” in isolation — compare deltas over a time window (for example, sample every 1–5 minutes and calculate the increase in `rejected` vs the increase in `completed`). Sustained non-zero `rejected` deltas indicate ongoing request drops (typically surfaced to clients as HTTP 429).

(we try to avoid Latin abbreviations: etc., e.g., i.e.,)

[stefnestor]

Usually at this level of detail we would recommend Monitoring (highlighting AutoOps).

But also, these two troubleshooting docs are really beginning to overlap 😂 & I'm not fully sure what to do. Cross-linking for concurrent PR where I requested your review as it sits in the bigger task backlog picture where I think this maybe would make more sense to explain: https://github.com/elastic/docs-content/pull/4657/files#diff-2ba649b230c054cba45dd0cc2039a0e546b92f16f09405a8b65c84a0e2007b3aR30

[kilfoyle]

Suggested change

	These errors are often related to [backlogged tasks](task-queue-backlog.md). See [this video](https://www.youtube.com/watch?v=auZJRXoAVpI) for a walkthrough of troubleshooting threadpool rejections.
	These errors are often related to [backlogged tasks](task-queue-backlog.md). See our [Threadpool Rejections video](https://www.youtube.com/watch?v=auZJRXoAVpI) for a troubleshooting walkthrough.

This just gives people a bit more certaintly about where the video link will take them, and also, just in case the link breaks, it gives them a title to search for.

[kilfoyle]

Suggested change

	Requests are arriving faster than workers can drain them (queue > 0). If it’s transient, it may be fine; if it persists/grows, it commonly precedes rejects.
	Requests are arriving faster than workers can drain them (queue > 0). If this state is transient, it may be fine; if the queue remains large or continues to grow, this commonly precedes rejects.

(just trying to avoid too many "it"s)

[kilfoyle]

LGTM! 🚀
Thanks a lot @rodrigomadalozzo! I've left a few minor phrasing comments but apart from those all looks good. 👍

[stefnestor]

:spiderman-jinx: 😂

I was also looking to cover this on the task queue backlog side because it matters just that it queues even if it doesn't reject (but I do like your expanded wording better if you wouldn't mind some plagiarizing / cross-pollinating?): https://github.com/elastic/docs-content/pull/4657/files#diff-2ba649b230c054cba45dd0cc2039a0e546b92f16f09405a8b65c84a0e2007b3aR39

[stefnestor]

🙏