一、平滑升级概述
Nginx方便地帮助我们实现了平滑升级。其原理简单概括，就是：
（1）在不停掉老进程的情况下，启动新进程。
（2）老进程负责处理仍然没有处理完的请求，但不再接受处理请求。
（3）新进程接受新请求。
（4）老进程处理完所有请求，关闭所有连接后，停止。
这样就很方便地实现了平滑升级。一般有两种情况下需要升级Nginx，一种是确实要升级Nginx的版本，另一种是要为Nginx添加新的模块。
二.、升级过程
具体的操作也很简单，如下：
（0）查看当前版本
在存放Nginx的可执行文件的目录下输入：
./nginx -V
（1）下载新的Nginx版本并编译。
wget nginx-1.0.11.tar.gz
tar zxvf nginx-1.0.11.tar.gz
cd nginx-1.0.11
./configure --add-module=/customized_module_0 --add-module=/customized_module_1
make
tar zxvf nginx-1.0.11.tar.gz
cd nginx-1.0.11
./configure --add-module=/customized_module_0 --add-module=/customized_module_1
make
注意不要进行make install
（2）备份老版本的可执行文件
cd /usr/local/nginx/sbin
sudo cp nginx nginx.old
sudo cp nginx nginx.old
（3）修改配置文件
如果有必要的话，进行配置文件的修改。
（4）拷贝新的可执行文件
sudo cp /home/michael/tmp/nginx-1.0.11/objs/nginx /usr/local/nginx/sbin/
（5）升级
cd /home/michael/tmp/nginx-1.0.11
make upgrade
make upgrade
（6）清理多余文件
rm -rf /home/michael/tmp/nginx-1.0.11
（7）查看Nginx版本
cd /usr/local/nginx/sbin
./nginx -V
./nginx -V
三、观察进程变化
在我的机器上可以观察到，我配置的是10个worker进程，启动后观察到：
root 6241 10419 0 10:51 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 6242 6241 2 10:51 ? 00:00:00 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6251 6241 1 10:51 ? 00:00:00 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
nobody 6253 6241 0 10:51 ? 00:00:00 nginx: cache loader process
luming 6310 25051 0 10:51 pts/1 00:00:00 grep --color=auto nginx
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
nobody 7998 10419 0 Jan12 ? 00:20:04 nginx: worker process is shutting down
nobody 8003 10419 0 Jan12 ? 00:20:12 nginx: worker process is shutting down
root 10419 1 0 Jan08 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 6242 6241 2 10:51 ? 00:00:00 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6251 6241 1 10:51 ? 00:00:00 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
nobody 6253 6241 0 10:51 ? 00:00:00 nginx: cache loader process
luming 6310 25051 0 10:51 pts/1 00:00:00 grep --color=auto nginx
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
nobody 7998 10419 0 Jan12 ? 00:20:04 nginx: worker process is shutting down
nobody 8003 10419 0 Jan12 ? 00:20:12 nginx: worker process is shutting down
root 10419 1 0 Jan08 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
可见新的进程有1个master和10个worker，另外还有1个老的master（可以从时间上看出）和4个worker（其他6个老的worker已经处理完所有连接而shutdown了）。还有一个loader进程。过几秒种可以看到worker只有两个了：
root 6241 10419 0 10:51 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 6242 6241 1 10:51 ? 00:00:00 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6251 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
nobody 6253 6241 0 10:51 ? 00:00:00 nginx: cache loader process
luming 6430 25051 0 10:51 pts/1 00:00:00 grep --color=auto nginx
nobody 7996 10419 0 Jan12 ? 00:20:11 nginx: worker process is shutting down
nobody 8003 10419 0 Jan12 ? 00:20:12 nginx: worker process is shutting down
root 10419 1 0 Jan08 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 6242 6241 1 10:51 ? 00:00:00 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6251 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
nobody 6253 6241 0 10:51 ? 00:00:00 nginx: cache loader process
luming 6430 25051 0 10:51 pts/1 00:00:00 grep --color=auto nginx
nobody 7996 10419 0 Jan12 ? 00:20:11 nginx: worker process is shutting down
nobody 8003 10419 0 Jan12 ? 00:20:12 nginx: worker process is shutting down
root 10419 1 0 Jan08 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
再过一小会儿观察：
root 6241 1 0 10:51 ? 00:00:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 6242 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6251 6241 0 10:51 ? 00:00:02 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
luming 8680 25051 0 10:56 pts/1 00:00:00 grep --color=auto nginx
nobody 6242 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6243 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6244 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6245 6241 0 10:51 ? 00:00:00 nginx: worker process
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 6248 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6249 6241 0 10:51 ? 00:00:00 nginx: worker process
nobody 6250 6241 0 10:51 ? 00:00:01 nginx: worker process
nobody 6251 6241 0 10:51 ? 00:00:02 nginx: worker process
nobody 6252 6241 0 10:51 ? 00:00:00 nginx: cache manager process
luming 8680 25051 0 10:56 pts/1 00:00:00 grep --color=auto nginx
Congratulations! You can upgrade your Nginx server gracefully.
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