安装：
npm install pm2 -g
更新：
pm2 update
pm2命令：
启动express项目命令：
pm2 start ./bin/www
打印日志：
pm2 logs
实时更新代码，不重启服务器，类似于热更新：watch起的作用（pm2 delete **.json && pm2 start **.json --env local）
灵活启动对应文件，加载对应环境代码(一)
{"apps": [{"name": "电子签约", "script": "./bin/www", "cwd": "./","watch": ["bin","lib","public","routes","views"],"log_date_format": "YYYY-MM-DD HH:mm Z","error_file":"/data/logs/electronic-err.log","out_file":"/data/logs/electronic-out.log", "env": {"NODE_ENV": "preview"}}]}//env里面可以配置自己想要的变量，例如：接口IP等NODE_ENV这块可以根据json文件的不同设定不同的参数，例如test、preview等
启动命令：pm2 deleteprocesses.json && pm2 start processes.json --env local对应相应的json文件
通过命令启动对应环境，环境变量：
启动命令：pm2 start ****.json --env local
{"apps": [{"name": "electronic","script": "./bin/www","cwd": "./","watch": ["bin","lib","public","routes","views"],"log_date_format": "YYYY-MM-DD HH:mm Z","error_file": "/data/logs/electronic-err.log","out_file": "/data/logs/electronic-out.log","env_local": {"NODE_ENV": "local"},"env_test": {"NODE_ENV": "test"},"env_preview": {"NODE_ENV": "preview"},"env_product": {"NODE_ENV": "product"}}]}
