%s Error serialising %s – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.4-8.9

Briefly, this error occurs when Elasticsearch struggles to serialize a specific object into JSON format. This could be due to complex data types or non-serializable objects. To resolve this issue, you can: 1) Ensure that the object you’re trying to serialize is compatible with JSON format. 2) Use a custom serializer to handle complex data types. 3) Check for null values or non-serializable fields in your data and handle them appropriately. 4) Update your Elasticsearch version as some older versions have known serialization issues.

This guide will help you check for common problems that cause the log ” [%s] Error serialising %s ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “[%s] Error serialising %s” classname is JobResultsPersister.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        private void indexResult(String id; ToXContent resultDoc; ToXContent.Params params; String resultType) {
            try (XContentBuilder content = toXContentBuilder(resultDoc; params)) {
                items.put(id; new IndexRequest(indexName).id(id).source(content));
            } catch (IOException e) {
                logger.error(() -> format("[%s] Error serialising %s"; jobId; resultType); e);

            if (items.size() >= JobRenormalizedResultsPersister.BULK_LIMIT) {


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