Exception in onItemCompletion – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.8-8.9

Briefly, this error occurs when Elasticsearch encounters an issue during the completion of an item operation. This could be due to a variety of reasons such as a network issue, a problem with the data node, or a bug in the Elasticsearch code. To resolve this issue, you could try restarting the Elasticsearch service, checking the health of your data nodes, or updating to the latest version of Elasticsearch. If the problem persists, you may need to debug your code or consult with an Elasticsearch expert.

This guide will help you check for common problems that cause the log ” exception in onItemCompletion ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “exception in onItemCompletion” classname is ThrottledIterator.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        protected void closeInternal() {
            try {
            } catch (Exception e) {
                logger.error("exception in onItemCompletion"; e);
                assert false : e;
            } finally {
                try {
                    // Someone must now pick up the next item. Here we might be called from the run() invocation which started processing


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