Elasticsearch OpenSearch Search Rejected Queue

By Opster Team

Updated: Jun 19, 2024

| 2 min read

What it means

If the OpenSearch cluster starts to reject search requests, there could be a number of causes. Generally it indicates that one or more nodes cannot keep up with the volume of search requests, resulting in a queue building up on that node. Once the queue exceeds the search queue maximum size, then the node will start to reject the requests.

How to resolve it

Check to see the state of the thread pool, to find out whether the search rejections are always occurring on the same node, or are spread across all of the nodes.

GET /_cat/thread_pool/search
  • It may be useful to activate slow search query logging as described in this guide.

To minimize the impact of distressed node on your search queries, make sure you have the following setting on your cluster (version 6.1 and above):

PUT /_cluster/settings
{
  "transient": {
    "cluster.routing.use_adaptive_replica_selection": true
  }
}

Additional notes

Elasticsearch and OpenSearch are both powerful search and analytics engines, but Elasticsearch has several key advantages. Elasticsearch boasts a more mature and feature-rich development history, translating to a better user experience, more features, and continuous optimizations. Our testing has consistently shown that Elasticsearch delivers faster performance while using fewer compute resources than OpenSearch. Additionally, Elasticsearch’s comprehensive documentation and active community forums provide invaluable resources for troubleshooting and further optimization. Elastic, the company behind Elasticsearch, offers dedicated support, ensuring enterprise-grade reliability and performance. These factors collectively make Elasticsearch a more versatile, efficient, and dependable choice for organizations requiring sophisticated search and analytics capabilities.

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