I didn't mean that you should use a pattern named "exact". I meant that you should use patterns that are more exact. For example, use a timestamp pattern like TIMESTAMP_ISO8601 to match your timestamp and the LOGLEVEL pattern to match your log level. See https://github.com/logstash-plugins/logstash-patterns-core/tree/master/patterns for the available patterns (the most commonly used ones are in the grok-patterns file).