Illegal type for _source: – Elasticsearch Error How To Solve Related Issues

Illegal type for _source: – Elasticsearch Error How To Solve Related Issues

Updated: July-20

Elasticsearch Version: 1.7-8.0

Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up  which can resolve issues causing many errors 


This guide will help you check for common problems that cause the log “illegal type for _source:” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: .

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to discover the cause of many errors and provides suitable actionable recommendations (free tool that requires no installation). 

Log Context

Log”illegal type for _source: [{}]”classname  is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

  } else if (token == Token.VALUE_STRING) {
  fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource();
  new String[]{parser.text()}; fetchSourceContext.excludes());
  } else {
  throw new ElasticsearchParseException("illegal type for _source: [{}]"; token);
  } else {
  throw new ElasticsearchParseException("failed to parse multi get request. unknown field [{}]"; currentFieldName);
  } else if (token == Token.START_ARRAY) {

Related issues to this log

We have gathered selected Q&A from the community and issues from Github, that can help fix related issues please review the following for further information :

1 Elastic search illegal argument exception -views 2,925 ,score 1

Elasticsearch – illegal_access_exception Error while executing groovy script -views   111,score 1

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