nginx worker process is shutting down

今天修改完nginx 的配置，重启之后，发现有 3个nginx进程是这样，其他5个左右都是正常的nginx; 看起来跟下图一样： ( today I met a strange case that some of my nginx processes become "is shutting down" status. )

nobody 6246 6241 0 10:51 ? 00:00:00 nginx: worker process 
nobody 6247 6241 0 10:51 ? 00:00:00 nginx: worker process 
nobody 6247 6241 0 10:51 ? 00:00:00 nginx: worker process 
nobody 6248 6241 0 10:51 ? 00:00:00 nginx: worker process 
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process 
nobody 7995 10419 0 Jan12 ? 00:20:37 nginx: worker process is shutting down 
nobody 7995 10419 0 Jan12 ? 00:20:37 nginx: worker process is shutting down 
nobody 7996 10419 0 Jan12 ? 00:20:11 nginx: worker process is shutting down 

经过google, 才知道这是 nginx -s reload之后， nginx 正在平滑的重启。(graceful reboot) 。 等调用对应nginx 的进程结束之后，这个process就会重启了。 (after googling, I found that the root cause is nginx's graceful reboot. the nginx process which shoud be shut down is still responding a request, and it will restart once the current request is done )

果然，大约20分钟后，这些进程都变成了 'worker process' 了。( 20 minutes later, all the nginx worker are rebooted )