Failed to detect JANSI s print stream encoding – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8-8.9

Briefly, this error occurs when Elasticsearch is unable to detect the JANSI’s print stream encoding. JANSI is a Java library that allows the use of ANSI escape sequences in console output. This error might be due to a misconfiguration or an unsupported environment. To resolve this issue, you can try updating your JANSI library to the latest version, ensure that your system supports ANSI escape sequences, or check your Elasticsearch configuration for any errors. If the problem persists, consider disabling JANSI or using a different method for console output.

This guide will help you check for common problems that cause the log ” Failed to detect JANSI’s print stream encoding ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “Failed to detect JANSI’s print stream encoding” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            return (Charset) charsetField.get(ansiOutputStream);
        } catch (Throwable t) {
            // has the library been upgraded and it now doesn't expose the same fields with the same names?
            // is the Security Manager installed preventing the access
  "Failed to detect JANSI's print stream encoding"; t);
            return null;


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