Concurrent modification of the index-N file expected current generation – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.13

Briefly, this error occurs when multiple processes are trying to modify the Elasticsearch index-N file simultaneously. This can happen due to a bug in the software or a misconfiguration. To resolve this issue, you can try the following: 1) Restart the Elasticsearch service to clear any locks on the file. 2) Check for any software bugs and apply patches if available. 3) Review your configuration to ensure only one process is allowed to modify the index-N file at a time. 4) If the error persists, consider rebuilding the index.

This guide will help you check for common problems that cause the log ” concurrent modification of the index-N file; expected current generation [ ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories, blobstore.

Log Context

Log “concurrent modification of the index-N file; expected current generation [” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 // snapshot delete run anyway.
 logger.debug("Determined repository's generation from its contents to [" + generation + "] but " +
 "current generation is at least [" + genToLoad + "]");
 if (genToLoad != repositoryStateId) {
 throw new RepositoryException(; "concurrent modification of the index-N file; expected current generation [" +
 repositoryStateId + "]; actual current generation [" + genToLoad + "]");
 if (cached != null && cached.generation() == genToLoad && cached.hasData()) {
 return cached.repositoryData();