Unexpected failure in %s – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.9-8.9

Briefly, this error occurs when Elasticsearch encounters an unexpected issue during a search operation. This could be due to a variety of reasons such as incorrect query syntax, insufficient memory, or a network connectivity issue. To resolve this, you can check the query syntax for any errors, ensure that Elasticsearch has enough memory to perform the operation, and verify that there are no network issues that could be causing the failure. Additionally, checking the Elasticsearch logs can provide more detailed information about the exact cause of the error.

This guide will help you check for common problems that cause the log ” unexpected failure in %s ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “unexpected failure in %s” classname is SnapshotShardsService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


            public void onFailure(Exception e) {
                logger.error(() -> Strings.format("unexpected failure in %s"; description()); e);
                assert false : e;

            public String toString() {


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