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

Opster Team

Aug-23, Version: 8.4-8.9

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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.

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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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