Unable to prewarm file – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 7.8-8.2

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Briefly, this error occurs when Elasticsearch tries to load data into the file system cache before it is needed but fails. This process, known as prewarming, improves search performance. The error could be due to insufficient disk space, incorrect file path, or permission issues. To resolve this, ensure there’s enough disk space, verify the file path is correct, and check if Elasticsearch has the necessary permissions to access the file. Also, consider adjusting the index settings to reduce the amount of data that needs to be prewarmed.

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This guide will help you check for common problems that cause the log ” {} unable to prewarm file [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “{} unable to prewarm file [{}]” classname is SearchableSnapshotDirectory.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            } catch (IOException e) {
                logger.warn(() -> new ParameterizedMessage("{} unable to prewarm file [{}]"; shardId; file.physicalName()); e);
                if (submitted == false) {


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