From: James Gray <james@...>
Date: 2009-04-25T04:17:54+09:00
Subject: Re: proper way to daemonize

On Apr 24, 2009, at 11:40 AM, Gary Wright wrote:
>
> On Apr 24, 2009, at 12:11 PM, James Gray wrote:
>
>> On Apr 24, 2009, at 11:01 AM, Gary Wright wrote:
>>
>>> On Apr 24, 2009, at 11:11 AM, Tim Pease wrote:
>>
>>>
>>>> This is the standard code to daemonize a process. The use of "exit"
>>>> bothers me slightly, as it will call all "at_exit" handlers in the
>>>> parent. I do not believe this is the desired behavior; the  
>>>> "at_exit"
>>>> handlers will free resources that the daemonized process might  
>>>> need.
>>>
>>> What resources are you talking about?  By the time exit is called,  
>>> the
>>> process has already been duplicated.  The child process won't be  
>>> affected
>>> by anything the parent does during via at_exit processing (at least
>>> with respect to Ruby object resources).
>>
>> But if that at_exit() handler deletes a file or something…
>
>
> Well, that is why I put the caveat about 'Ruby object resources'.
> Isn't it fair to assume the at_exit code isn't actively hostile? :-)
>
> If you've got at_exit() code that is trashing external resources  
> that are used by a child process, that is a bug to be fixed I think  
> rather than a bug to be obscured via exit!

Seems like Tim has a pretty decent example where the behavior doesn't  
feel buggy.

Basically, I view it this way.  The exit() calls in a daemonize()  
method aren't the typical usage.  Normally, exit() is used to end a  
process.  Our process isn't really ending though so much as  
transitioning into a different kind of process.  exit() is just an  
implementation detail of how that transition occurs.  As such, exit!()  
feels more correct to me because I don't want to go through a shutdown  
sequence of the original process, I just want the first to immediately  
cease to exist while the second takes over for it.

That's all just my opinion though.  Feel free to ignore.

James Edward Gray II