为什么有的时候开机，redis没有自动起来呢？

Question

不常见，但有的时候开机redis没有自个启动，不知道如何查找原因，请高人指点

$ redis-cli
Could not connect to Redis at 127.0.0.1:6379: Connection refused

我看了下日至，如下

[207] 29 Sep 18:22:41.020 * 1 changes in 900 seconds. Saving...
[207] 29 Sep 18:22:41.099 * Background saving started by pid 2473
[2473] 29 Sep 18:22:41.685 * DB saved on disk
[207] 29 Sep 18:22:42.014 * Background saving terminated with success
[207 | signal handler] (1380450274) Received SIGTERM, scheduling shutdown...
[207] 29 Sep 18:24:34.759 # User requested shutdown...
[207 | signal handler] (1380450274) Received SIGTERM, scheduling shutdown...
[207] 29 Sep 18:24:34.899 * Saving the final RDB snapshot before exiting.
[207] 29 Sep 18:24:35.050 * DB saved on disk
[207] 29 Sep 18:24:35.050 * Removing the pid file.
[207] 29 Sep 18:24:35.150 # Redis is now ready to exit, bye bye...
[620] 29 Sep 21:50:35.953 * Max number of open files set to 10032
                _._
           _.-``__ ''-._
      _.-``    `.  `_.  ''-._           Redis 2.6.14 (00000000/0) 64 bit
  .-`` .-".  "\/    _.,_ ''-._
 (    '      ,       .-`  | `,    )     Running in stand alone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 620
  `-._    `-._  `-./  _.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |           http://redis.io
  `-._    `-._`-.__.-'_.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |
  `-._    `-._`-.__.-'_.-'    _.-'
      `-._    `-.__.-'    _.-'
          `-._        _.-'
              `-.__.-'

[620] 29 Sep 21:50:35.971 # Server started, Redis version 2.6.14
[620] 29 Sep 21:50:35.984 * DB loaded from disk: 0.013 seconds
[620] 29 Sep 21:50:35.984 * The server is now ready to accept connections on port 6379

好像也没有异常，上面提到的

[207] 29 Sep 18:24:35.050 * Removing the pid file.

因该是我关机的缘故，pid删除了，一般的情况下，开机会自动启动pid的，但是这次没有，上面启动界面是我最有一次手动启动的log信息

Answer 1

redis在启动的时候会为信号SIGTERM注册信号处理函数，该函数会让redis在结束运行之前做些资源清理工作，譬如保存RDB文件，删除PID文件（如果redis是以daemon方式运行）等等，当这些工作都做完后，调用exit函数退出

所以日志这段内容：

[207 | signal handler] (1380450274) Received SIGTERM, scheduling shutdown...
[207] 29 Sep 18:24:34.759 # User requested shutdown...
[207 | signal handler] (1380450274) Received SIGTERM, scheduling shutdown...
[207] 29 Sep 18:24:34.899 * Saving the final RDB snapshot before exiting.
[207] 29 Sep 18:24:35.050 * DB saved on disk
[207] 29 Sep 18:24:35.050 * Removing the pid file.
[207] 29 Sep 18:24:35.150 # Redis is now ready to exit, bye bye.

都是符合上述我说的流程，收到SIGTERM信号 -> 处理资源 -> 结束redis服务

但是后面这些日志，看时间应该和上面的不是同一个：

[620] 29 Sep 21:50:35.953 * Max number of open files set to 10032

所以我觉得问题的关键是为什么在Redis启动的时候会收到一个SIGTERM信号?