如何优雅的退出/关闭/重启gunicorn进程
在工作中，会发现gunicorn启动的web服务，无论怎么使用kill -9 进程号都是无法杀死gunicorn，经过我一番百度和谷歌，发现想要删除gunicorn进程其实很简单。
1. 寻找masterpid
通过执行如下命令，可以获取Gunicorn进程树：
pstree -ap|grep gunicorn
得到如下的结果。
|-grep,6194 --col gunicorn
| `-gunicorn,30080 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,4413 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,8030 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,8135 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,8137 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,11532 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,13460 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,19728 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,23585 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,23825 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,27921 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,28899 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,28900 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,28901 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,35637 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,36963 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,43074 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,43118 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,43232 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,43307 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,43308 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,44018 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,46996 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| |-gunicorn,47000 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
| `-gunicorn,47650 /usr/local/bin/gunicorn collect:app -c collect_gunicorn.py
很显然，30080就是Gunicorn的主进程。
2. 重启Gunicorn任务
按照官方的推荐方法，很容易执行命令：
kill -HUP 30080
执行上述命令后，再次执行“pstree -ap|grep gunicorn”，我们很容易发现，除了主进程，其他的Gunicorn进程都已经销毁，并新建了进程（进程ID发生了变化）。
3. 退出Gunicorn任务
kill -9 30080
