Error closing netty event loop group – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch fails to close the Netty event loop group, which is responsible for handling network events. This could be due to a network issue, a bug in the software, or a system resource constraint. To resolve this issue, you can try restarting OpenSearch, checking for any network issues, or upgrading OpenSearch to the latest version. If the problem persists, consider checking the system resources and increasing them if necessary. Also, ensure that the Netty event loop group is properly initialized and closed in your code.

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This guide will help you check for common problems that cause the log ” Error closing netty event loop group ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: netty.

Log Context

Log “Error closing netty event loop group” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

        protected void closeInternal() {
            Future> shutdownFuture = eventLoopGroup.shutdownGracefully(0; 5; TimeUnit.SECONDS);
            if (shutdownFuture.isSuccess() == false) {
                logger.warn("Error closing netty event loop group"; shutdownFuture.cause());



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