Invalid year month value for field expected string number value or an – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.15

Briefly, this error occurs when Elasticsearch encounters an invalid year-month value for a specific field. It expects a string or number value or an array of these types. This could be due to incorrect data format or type mismatch. To resolve this, ensure that the data being indexed matches the expected format. If it’s a date field, it should be in a valid date format. If it’s a number, ensure it’s not being passed as a string. Also, check your mapping to ensure the field type is correctly defined.

This guide will help you check for common problems that cause the log ” invalid year month value for [{}] field. expected string/number value or an ” 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 for [{}] field. expected string/number value or an” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 } else if (token == XContentParser.Token.START_ARRAY) {
 while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
 monthsSet.add(parseMonthValue(parser; token));
 } else {
 throw new ElasticsearchParseException("invalid year month value for [{}] field. expected string/number value or an " +
 "array of string/number values; but found [{}]"; currentFieldName; token);
 } else if (DAY_FIELD.match(currentFieldName; parser.getDeprecationHandler())) {
 if (token.isValue()) {
 daysSet.add(MonthTimes.parseDayValue(parser; token));


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