离线安装
下载插件包：
例如需要下载exec包，在github网站 https://github.com/logstash-plugins/logstash-output-exec 下载 exec包。
logstash-output-exec-master.zip
安装：
将exec包上传到Logstash所在的服务器并解压到目录：/opt/logstash/plugins下
修改Logstash的Gemfile文件，再最后添加一行：gem "logstash-output-exec", :path => "/opt/logstash/plugins"
最后执行安装：bin/logstash-plugin install --no-verify
Installing...
Installation successful
OK......
测试：
省略。。。
在线安装
需要修改为国内的源：
$ vim /opt/logstash-5.1.1/Gemfile
# This is a Logstash generated Gemfile.
# If you modify this file manually all comments and formatting will be lost.
source "https://rubygems.org"
gem "logstash-core", :path => "./logstash-core"
gem "logstash-core-queue-jruby", :path => "./logstash-core-queue-jruby"
gem "logstash-core-event-java", :path => "./logstash-core-event-java"
gem "logstash-core-plugin-api", :path => "./logstash-core-plugin-api"
保存并执行：bin/logstash-plugin install logstash-output-exec
