Doesn't seem to happen all that much, but still probably worth looking into at some point.
{
"_index": "logstash-2017.10.17",
"_type": "elasticsearch",
"_id": "AV8qg6Z0TqnoMLVnwvus",
"_score": null,
"_source": {
"LoggerName": "org.wikimedia.highlighter.experimental.elasticsearch.ExperimentalHighlighter",
"source_host": "10.64.0.235",
"level": "ERROR",
"Severity": "ERROR",
"Time": "2017-10-17 13:26:31,0316",
"type": "elasticsearch",
"message": "Failed to highlight field [java.lang.StringIndexOutOfBoundsException: String index out of range: -5]",
"normalized_message": "Failed to highlight field [java.lang.StringIndexOutOfBoundsException: String index out of range: -5]",
"SourceMethodName": "highlight",
"Thread": "elasticsearch[elastic1034][search][T#28]",
"tags": [
"es",
"gelf",
"normalized_message_untrimmed"
],
"@timestamp": "2017-10-17T13:26:31.319Z",
"SourceSimpleClassName": "ExperimentalHighlighter",
"host": "elastic1034",
"@version": "1",
"SourceClassName": "org.wikimedia.highlighter.experimental.elasticsearch.ExperimentalHighlighter",
"gelf_level": "3",
"SourceLineNumber": 75,
"timestamp": "1508246791.316"
},
"fields": {
"@timestamp": [
1508246791319
]
},
"sort": [
1508246791319
]
}