IO error creating collector – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch is unable to create a collector due to an Input/Output (IO) issue. This could be due to insufficient disk space, file system permission issues, or hardware failures. To resolve this, you can free up disk space, check and correct file system permissions, or investigate potential hardware issues. Additionally, ensure that Elasticsearch has enough heap memory allocated. If the issue persists, consider reindexing your data or upgrading your Elasticsearch version.

This guide will help you check for common problems that cause the log ” IO error creating collector ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: search, aggregations.

Log Context

Log “IO error creating collector” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 tdc = createTopDocsCollector(shardSize);
 currentLeafCollector = tdc.getLeafCollector(aggCtx.getLeafReaderContext());
 } catch (IOException e) {
 throw new ElasticsearchException("IO error creating collector"; e);
 }  public void getMatches(List allDocs) {
 TopDocs topDocs = tdc.topDocs();


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