[[rejected-requests]]
=== Rejected requests

When {es} rejects a request, it stops the operation and returns an error with a
`429` response code. Rejected requests are commonly caused by:

* A <<high-cpu-usage,depleted thread pool>>. A depleted `search` or `write`
thread pool returns a `TOO_MANY_REQUESTS` error message.

* A <<circuit-breaker-errors,circuit breaker error>>.

* High <<index-modules-indexing-pressure,indexing pressure>> that exceeds the
<<memory-limits,`indexing_pressure.memory.limit`>>.

[discrete]
[[check-rejected-tasks]]
==== Check rejected tasks

To check the number of rejected tasks for each thread pool, use the
<<cat-thread-pool,cat thread pool API>>. A high ratio of `rejected` to
`completed` tasks, particularly in the `search` and `write` thread pools, means
{es} regularly rejects requests.

[source,console]
----
GET /_cat/thread_pool?v=true&h=id,name,active,rejected,completed
----

[discrete]
[[prevent-rejected-requests]]
==== Prevent rejected requests

**Fix high CPU and memory usage**

If {es} regularly rejects requests and other tasks, your cluster likely has high
CPU usage or high JVM memory pressure. For tips, see <<high-cpu-usage>> and
<<high-jvm-memory-pressure>>.

**Prevent circuit breaker errors**

If you regularly trigger circuit breaker errors, see <<circuit-breaker-errors>>
for tips on diagnosing and preventing them.