pm2日志记录和日志分割

pm2介绍

pm2是nodejs进程管理工具，现在基本是node生产服务器的标准选择，可以帮助我们实现node多进程服务，开启的多个实例自动实现负载均衡。最重要的是保证node单进程不会因为错误退出，作为守护进程保证nodejs服务不宕机。总体来说就是有性能监控、自动重启、负载均衡的作用。

pm2-logrotate介绍

pm2本身是可以输出日志文件的，默认的文件路径：

error log path    │ /home/username/.pm2/logs/app-error-0.log

out log path      │ /home/username/.pm2/logs/app-out-0.log

但是pm2的日志文件不能自动分割，这会导致一个文件不断变大，不但影响性能，查看这些日志也会带来麻烦。所以需要pm2-logrotate来实现自动分割日志。

安装pm2-logrotate

pm2 install pm2-logrotate,是用pm2命令，不是npm命令

pm2-logrotate配置

``max_size` (默认 10M): 最大为多少时进行分割，例如: 10G, 10M, 10K
``retain` (Defaults to all): This number is the number of rotated logs that are keep at any one time, it means that if you have retain = 7 you will have at most 7 rotated logs and your current one.
compress (默认 false): 是否压缩日志
dateFormat (默认 YYYY-MM-DD_HH-mm-ss) : 日志格式
rotateModule (Defaults to true) : Rotate the log of pm2's module like other apps
workerInterval (Defaults to 30 in secs) : You can control at which interval the worker is checking the log's size (minimum is 1)
rotateInterval (Defaults to 0 0 * * * everyday at midnight): This cron is used to a force rotate when executed. We are using node-schedule to schedule cron, so all valid cron for node-schedule is valid cron for this option. Cron style :
TZ (Defaults to system time): This is the standard tz database timezone used to offset the log file saved. For instance, a value of Etc/GMT-1, with an hourly log, will save a file at hour 14 GMT with hour 13 GMT-1 in the log name.

*    *    *    *    *    *

┬    ┬    ┬    ┬    ┬    ┬

│    │    │    │    │    |

│    │    │    │    │    └ day of week (0 - 7) (0 or 7 is Sun)

│    │    │    │    └───── month (1 - 12)

│    │    │    └────────── day of month (1 - 31)

│    │    └─────────────── hour (0 - 23)

│    └──────────────────── minute (0 - 59)

└───────────────────────── second (0 - 59, OPTIONAL)

可以尝试使用pm2 set pm2-logrotate:max_size 1K (1KB)设置日志文件最大为1KB 代码中console.log的内容会输出到 /home/username/.pm2/logs/app-out-0.log, 大小达到1KB就会自动生成 app-out-0__2018-01-25_16-58-16.log这种格式的日志文件。在/home/username/.pm2/logs/（默认路径，可以配置）路径下还有

app-error-0.log
pm2-logrotate-out-1.log
pm2-logrotate-error-1.log 几个文件，app-out-0.log文件记录的就是console.log输出，app-error-0.log记录的是错误输出，pm2-logrotate-out-1.log和pm2-logrotate-error-1.log分别记录的是分割的日志文件，是这样的内容：

"/home/username/.pm2/pm2__2018-01-25_16-57-16.log" has been created

"/home/username/.pm2/logs/app-out-0__2018-01-25_16-58-16.log" has been created

"/home/username/.pm2/logs/app-out-0__2018-01-25_16-58-46.log" has been created