Unexpected failure during – How to solve related issues

Unexpected failure during – How to solve related issues

Opster Team

Jan-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.

This guide will help you check for common problems that cause the log ” Unexpected failure during ” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: admin and cluster.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).

Log Context

Log “Unexpected failure during [{}]” classname is TransportClusterHealthAction.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                         listener.onFailure(new NotMasterException("no longer master. source: [" + source + "]"));

                    public void onFailure(String source; Exception e) {
                        logger.error(() -> new ParameterizedMessage("unexpected failure during [{}]"; source); e);
        } else {


Run the Check-Up to get a customized report like this:

Analyze your cluster