Failed to acquire searcher source – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.9

Briefly, this error occurs when Elasticsearch is unable to obtain a searcher instance, possibly due to resource constraints or internal issues. This could be caused by high load, insufficient memory, or a bug in the software. To resolve this issue, you can try to increase the system resources, particularly memory, reduce the load on the Elasticsearch cluster by optimizing your queries, or upgrade Elasticsearch to the latest version to fix potential bugs. Also, ensure that your Elasticsearch cluster is properly configured and that there are no network issues that could be causing this problem.

This guide will help you check for common problems that cause the log ” failed to acquire searcher; source ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: source, index.

Log Context

Log “failed to acquire searcher; source” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 throw ex;
 } catch (Exception ex) {
 maybeFailEngine("acquire_searcher"; ex);
 ensureOpen(ex); // throw EngineCloseException here if we are already closed
 logger.error(() -> new ParameterizedMessage("failed to acquire searcher; source {}"; source); ex);
 throw new EngineException(shardId; "failed to acquire searcher; source " + source; ex);
 } finally {


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