项目地址：
https://github.com/BonnierNews/logstash_exporter
build插件：
[xxx@logstash3 ~]$ yum install -y go
[xxx@logstash3 ~]$ cd go/src/github.com/BonnierNews/logstash_exporter
[xxx@logstash3 ~]$ make
[xxx@logstash3 ~]$ ls -al logstash_exporter
[xxx@logstash3 ~]$ cp logstash_exporter /usr/local/bin/logstash_exporter
[xxx@logstash3 ~]$ /usr/local/bin/logstash_exporter --help
usage: logstash_exporter [<flags>]
Flags:
-h, --help Show context-sensitive help (also try --help-long and --help-man).
--logstash.endpoint="http://localhost:9600"
The protocol, host and port on which logstash metrics API listens
--web.listen-address=":9198"
Address on which to expose metrics and web interface.
--log.level="info" Only log messages with the given severity or above. Valid levels: [debug, info, warn, error, fatal]
--log.format="logger:stderr"
Set the log target and format. Example: "logger:syslog?appname=bob&local=7" or "logger:stdout?json=true"
--version Show application version.
启动logstash_exporter
/usr/local/bin/logstash_exporter
访问metrics: curl http://localhost:9198/metrics
Grafana画图：
https://grafana.com/dashboards/2525
