[GitHub] [dolphinscheduler] rickchengx commented on pull request #12118: [Fix-12109] Fix the errors when starting 2 times with dolphinscheduler-daemon.sh

[GitBox <gi...@apache.org>]

rickchengx commented on PR #12118:
URL: https://github.com/apache/dolphinscheduler/pull/12118#issuecomment-1261660941

   > IMHO, i think that pid file may not a good idea, because pid just can keep only one process pid
   > 
   > 1. If there are two Master process running at same time, but this status function just find one. Becuase if use just call start.sh may start a process again.
   > 2. If user use `kill` command, cannot clear this pid
   > 3. Some misopeation may clear or modify this pid file.
   >    i think the result of using the `ps -ef` check is more accurate and reliable. Personal opinion,just for reference.
   
   Hi, @DarkAssassinator , thanks a lot for the comment. Sorry for the late response.
   
   > If the user starts DS twice (or more) using dolphinscheduler-daemon.sh, the pid file will be overwritten, making it impossible to stop the initially started DS cluster.
   
   1. In fact, the purpose of this PR is to limit the user to start DS twice. When the user starts a server, it will first determine whether it has been started. If the server is already started, the script will cancel this launch.
   
   2. As for using pid file to check the status may not be a good option, for example pid may be modified artificially. But currently the script uses the pid file to kill the process, facing the same problem. And the original approach (`grep #DOLPHINSCHEDULER_HOME`) is also likely to cause errors. Since there is no complete guarantee that other processes do not meet the filter criteria.
   
   3. I think the script should take the **same approach** to get the process when checking the process status and killing the process (`grep ...` or check the `pid`). And I personally prefer to check the `pid` file because it's a way used by a lot of programs on linux.


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