Failed to load ICU rule files – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch is unable to load International Components for Unicode (ICU) rule files, which are essential for handling Unicode text and providing Unicode services. This could be due to missing or incorrectly configured ICU plugin. To resolve this issue, you can try reinstalling the ICU plugin, ensuring that the plugin is compatible with your Elasticsearch version. Also, check the file permissions and paths to ensure Elasticsearch can access the ICU rule files. Lastly, verify your Elasticsearch configuration settings related to ICU.

This guide will help you check for common problems that cause the log ” failed to load ICU rule files ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, plugins, analysis.

Log Context

Log “failed to load ICU rule files” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 return tokenizerConfig;
 } catch (Exception e) {
 throw new ElasticsearchException("failed to load ICU rule files"; e);
 }  // parse a single RBBi rule file
 private BreakIterator parseRules(String filename; Environment env) throws IOException {


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