Invalid year month value expected a string or a number value but found – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when Elasticsearch tries to parse a date field but encounters an unexpected data type. It expects a string or a number but found a different data type. To resolve this issue, you can check the data you’re trying to index and ensure that the date fields are either strings in the correct date format or numbers representing epoch time. Also, ensure that your mapping correctly defines the field as a date type. If the error persists, you may need to clean your data to remove or convert non-conforming values.

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This guide will help you check for common problems that cause the log ” invalid year month value. expected a string or a number value; but found [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “invalid year month value. expected a string or a number value; but found [{}]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 return Month.resolve(parser.text());
 if (token == XContentParser.Token.VALUE_NUMBER) {
 return Month.resolve(parser.intValue());
 throw new ElasticsearchParseException("invalid year month value. expected a string or a number value; but found [{}]"; token);
 }  public static class Builder {  private final Set months = new HashSet<>();


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