Failed to find format – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.

This guide will help you check for common problems that cause the log ” Failed to find format ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: fielddata and index.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up to analyze Elasticsearch configuration and help resolve this error.

Log Context

Log “failed to find format [” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

             format = null;
        if (format != null) {
            builder = buildersByTypeAndFormat.get(Tuple.tuple(type.getType(); format));
            if (builder == null) {
                logger.warn("failed to find format [" + format + "] for field [" + fieldNames.fullName() + "]; will use default");
        if (builder == null && docValues) {
            builder = docValuesBuildersByType.get(type.getType());


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