Dropping a warning header as their total size reached the maximum allowed of – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-7.15

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Briefly, this error occurs when the total size of warning headers in Elasticsearch exceeds the maximum limit allowed. This is often due to a large number of warnings generated by queries or operations. To resolve this issue, you can either increase the maximum allowed size of warning headers in the Elasticsearch settings or reduce the number of warnings by optimizing your queries and operations. Additionally, regularly monitoring and addressing warnings can prevent them from accumulating and exceeding the limit.

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This guide will help you check for common problems that cause the log ” Dropping a warning header; as their total size reached the maximum allowed of [ ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “Dropping a warning header; as their total size reached the maximum allowed of [” classname is ThreadContext.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            assert value != null;
            long newWarningHeaderSize = warningHeadersSize;
            //check if we can add another warning header - if max size within limits
            if (key.equals("Warning") && (maxWarningHeaderSize != -1)) { //if size is NOT unbounded; check its limits
                if (warningHeadersSize > maxWarningHeaderSize) { // if max size has already been reached before
                    logger.warn("Dropping a warning header; as their total size reached the maximum allowed of ["
                            + maxWarningHeaderSize + "] bytes set in ["
                            + HttpTransportSettings.SETTING_HTTP_MAX_WARNING_HEADER_SIZE.getKey() + "]!");
                    return this;
                newWarningHeaderSize += "Warning".getBytes(StandardCharsets.UTF_8).length + value.getBytes(StandardCharsets.UTF_8).length;


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