Unable to close Groovy loader – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

Briefly, this error occurs when Elasticsearch is unable to close the Groovy scripting engine’s class loader. This could be due to a lack of system resources or a bug in the Groovy scripting engine. To resolve this issue, you can try restarting Elasticsearch, increasing system resources, or disabling Groovy scripting if it’s not necessary for your use case. Alternatively, consider upgrading Elasticsearch to a newer version where Groovy is replaced by Painless scripting language, which is safer and more efficient.

This guide will help you check for common problems that cause the log ” Unable to close Groovy loader ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: Index and Memory.

Log Context

Log “Unable to close Groovy loader” classname is GroovyScriptEngineService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            public Void run() {
                try {
                } catch (IOException e) {
                    logger.warn("Unable to close Groovy loader"; e);
                return null;


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