Discovery-file Failed to find unicast hosts file – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.

To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.

This guide will help you check for common problems that cause the log ” Discovery-file Failed to find unicast hosts file ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: discovery, discovery-file, hosts and plugins.

Log Context

Log “[discovery-file] Failed to find unicast hosts file [{}]” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

         List hostsList;
        try (Stream lines = Files.lines(unicastHostsFilePath)) {
            hostsList = lines.filter(line -> line.startsWith("#") == false) // lines starting with `#` are comments
        } catch (FileNotFoundException | NoSuchFileException e) {
            logger.warn((Supplier>) () -> new ParameterizedMessage("[discovery-file] Failed to find unicast hosts file [{}]";
                                                                        unicastHostsFilePath); e);
            hostsList = Collections.emptyList();
        } catch (IOException e) {
            logger.warn((Supplier>) () -> new ParameterizedMessage("[discovery-file] Error reading unicast hosts file [{}]";
                                                                        unicastHostsFilePath); e);


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