docker-erlang-example/advanced_examples/elk/logstash/logstash.conf

input {
    gelf {
        use_udp => true
        port => 44622
    }
}
filter {
    # If a log message can be parsed as json, do so, and populate the
    # log event with fields found.
    json {
        skip_on_invalid_json => "true"
        source => "message"
    }
    # Convert the level field to an integer
    mutate {
        convert => {
            "level" => "integer"
        }
    }
}
output {
    file {
        path => "/usr/share/logstash/logs/output.log"
    }
    elasticsearch {
        hosts => ["elasticsearch:9200"]
	http_compression => true
    }
}