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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 depleted thread pool. A depleted
searchorwritethread pool returns aTOO_MANY_REQUESTSerror message. - A circuit breaker error.
- High indexing pressure that exceeds the
indexing_pressure.memory.limit.
::::{tip} If you're using Elastic Cloud Hosted, then you can use AutoOps to monitor your cluster. AutoOps significantly simplifies cluster management with performance recommendations, resource utilization visibility, and real-time issue detection with resolution paths. For more information, refer to Monitor with AutoOps.
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To check the number of rejected tasks for each thread pool, use the 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.
GET /_cat/thread_pool?v=true&h=id,name,queue,active,rejected,completedwrite thread pool rejections frequently appear in the erring API and correlating log as EsRejectedExecutionException with either QueueResizingEsThreadPoolExecutor or queue capacity.
These errors are often related to backlogged tasks.
See this video for a walkthrough of troubleshooting threadpool rejections.
To check the number of tripped circuit breakers, use the node stats API.
GET /_nodes/stats/breakerThese statistics are cumulative from node startup. For more information, see circuit breaker errors.
See this video for a walkthrough of diagnosing circuit breaker errors.
To check the number of indexing pressure rejections, use the node stats API.
GET _nodes/stats?human&filter_path=nodes.*.indexing_pressureThese stats are cumulative from node startup.
Indexing pressure rejections appear as an EsRejectedExecutionException, and indicate that they were rejected due to combined_coordinating_and_primary, coordinating, primary, or replica.
These errors are often related to backlogged tasks, bulk index sizing, or the ingest target's refresh_interval setting.
See this video for a walkthrough of diagnosing indexing pressure rejections.
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.