Briefly, this error occurs when Elasticsearch encounters an unexpected token after a specific field name during query parsing. This usually happens due to incorrect query syntax or structure. To resolve this issue, you can: 1) Review and correct the query syntax, ensuring it adheres to the Elasticsearch query DSL. 2) Check for any misplaced or missing punctuation in the query. 3) Validate the query using a tool like Kibana’s Dev Tools before executing it.
This guide will help you check for common problems that cause the log ” unexpected token [” + token + “] after [” + fieldName + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: search.
Overview
Search refers to the searching of documents in an index or multiple indices. The simple search is just a GET API request to the _search endpoint. The search query can either be provided in query string or through a request body.
Examples
When looking for any documents in this index, if search parameters are not provided, every document is a hit and by default 10 hits will be returned.
GET my_documents/_search
A JSON object is returned in response to a search query. A 200 response code means the request was completed successfully.
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 2,
"successful" : 2,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 1.0,
"hits" : [
...
]
}
}Notes and good things to know
- Distributed search is challenging and every shard of the index needs to be searched for hits, and then those hits are combined into a single sorted list as a final result.
- There are two phases of search: the query phase and the fetch phase.
- In the query phase, the query is executed on each shard locally and top hits are returned to the coordinating node. The coordinating node merges the results and creates a global sorted list.
- In the fetch phase, the coordinating node brings the actual documents for those hit IDs and returns them to the requesting client.
- A coordinating node needs enough memory and CPU in order to handle the fetch phase.
Log Context
Log “unexpected token [” + token + “] after [” + fieldName + “]” class name is SuggestBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
if (suggestionName == null) {
throw new IllegalArgumentException("suggestion must have name");
}
suggestBuilder.addSuggestion(suggestionName; SuggestionBuilder.fromXContent(parser));
} else {
throw new ParsingException(parser.getTokenLocation(); "unexpected token [" + token + "] after [" + fieldName + "]");
}
}
return suggestBuilder;
}
