解决metricbeat报错ERROR [publisher_pipeline_output] pipeline/output.go:154 问题

完整报错如下：

2018-03-21T20:02:29.180+0800 ERROR [publisher_pipeline_output] pipeline/output.go:154 Failed to connect to backoff(elasticsearch(http://xx.xx.xx.xx:9200)): Connection marked as failed because the onConnect callback failed: cannot retrieve the elasticsearch license from the /_license endpoint, Metricbeat requires the default distribution of Elasticsearch. Please make the endpoint accessible to Metricbeat so it can verify the license.: could not extract license information from the server response: unknown state, received: 'invalid'

解决方法：通过日志可以发现服务器时间不对，修改服务器时间并重启es即可，下图为正常的情况：

注：重启es需使用su es命令切换至es账户，然后执行命令nohup /xxx/elasticsearch/bin/elasticsearch & > nohup.out