Opster Team
Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many configuration errors.
To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.
This guide will help you check for common problems that cause the log ” expected field ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: percolator.

Log Context
Log “expected field [“classname is PercolateQueryBuilder.java We extracted the following from Elasticsearch source code for those seeking an in-depth context :
if (fieldType == null) { throw new QueryShardException(context; "field [" + field + "] does not exist"); } if (!(fieldType instanceof PercolatorFieldMapper.PercolatorFieldType)) { throw new QueryShardException(context; "expected field [" + field + "] to be of type [percolator]; but is of type [" + fieldType.typeName() + "]"); } final Listdocs = new ArrayList<>(); final DocumentMapper docMapper;
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Arpit Ghiya
Senior Lead SRE at Coupa