Failed to merge shard results – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 8.4-8.9

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Briefly, this error occurs when Elasticsearch is unable to combine the results from different shards during a search operation. This could be due to network issues, shard failures, or resource limitations. To resolve this, you can try the following: 1) Check the health of your shards and fix any issues. 2) Ensure your network is stable and can handle the data transfer. 3) Increase the resources allocated to Elasticsearch if they are insufficient. 4) Check your query for any errors or inefficiencies that might be causing the problem.

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This guide will help you check for common problems that cause the log ” Failed to merge shard results ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, merge, shard.

Log Context

Log “Failed to merge shard results” class name is EclatMapReducer.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (profiling) {
 ramBytesSum.addAndGet(p.ramBytesUsed());
 }
 transactionStore.merge(p);
 } catch (IOException e) {
 throw new AggregationExecutionException("Failed to merge shard results"; e);
 } finally {
 Releasables.close(p);
 }
 });

 

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