SIGWINCH

SIGWINCH

[Lawrence Pit]

Hi,

I followed the procedure to replace a running unicorn. Works fine, 
except for one thing: after I decide to back out, ie I send a HUP to the 
old master followed by a QUIT to the new master, then:

1. the new master does die, and the old master does work again

2. the "old" master keeps running with a process name of "master (old)"

3. the "old" master keeps running with a pid file named unicorn.pid.oldbin

Because the file is now named unicorn.pid.oldbin a later attempt to 
deploy using scripts is made rather difficult as they assume a pid file 
named unicorn.pid.

How could I get unicorn to rename the pid file back to unicorn.pid ?  I 
see some code in method +reap_all_workers+ that suggests it would rename 
the pid file back to its original, but for some reason it doesn't for 
me. Am I missing a step?


PS. Using unicorn 1.1.1.



Cheers,
Lawrence
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Re: SIGWINCH

[Eric Wong]

Lawrence Pit <lawrence.pit@gmail.com> wrote:
> Hi,
>
> I followed the procedure to replace a running unicorn. Works fine,  
> except for one thing: after I decide to back out, ie I send a HUP to the  
> old master followed by a QUIT to the new master, then:
>
> 1. the new master does die, and the old master does work again
>
> 2. the "old" master keeps running with a process name of "master (old)"
>
> 3. the "old" master keeps running with a pid file named unicorn.pid.oldbin
>
> Because the file is now named unicorn.pid.oldbin a later attempt to  
> deploy using scripts is made rather difficult as they assume a pid file  
> named unicorn.pid.
>
> How could I get unicorn to rename the pid file back to unicorn.pid ?  I  
> see some code in method +reap_all_workers+ that suggests it would rename  
> the pid file back to its original, but for some reason it doesn't for  
> me. Am I missing a step?

Hi Lawrence,

Are you using a config file to specify pid or --pid from the
command-line?  The config file should be more reliable.  I'll take a
deeper look at it in a bit.

-- 
Eric Wong
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Re: SIGWINCH

[Lawrence Pit]

> > How could I get unicorn to rename the pid file back to unicorn.pid ?  I  
> > see some code in method +reap_all_workers+ that suggests it would rename  
> > the pid file back to its original, but for some reason it doesn't for  
> > me. Am I missing a step?
> 
> Hi Lawrence,
> 
> Are you using a config file to specify pid or --pid from the
> command-line?  The config file should be more reliable.  I'll take a
> deeper look at it in a bit.
> 

Hi Eric,

I'm using both. I have an /etc/init.d/unicorn script which is somewhat like your
examples/init.sh (using start-stop-daemon instead of kill though) and a config
file that is like your examples/unicorn_conf.rb (comments left untouched).



Cheers,
Lawrence

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Re: SIGWINCH

[Lawrence Pit]

> Are you using a config file to specify pid or --pid from the
> command-line?  The config file should be more reliable.  I'll take a
> deeper look at it in a bit.
>   

fwiw, this is the /etc/init.d/unicorn script I'm using so far:

http://gist.github.com/473547

Perhaps it's of use to others as well.


Background: the main feature I'm looking for is to deploy code using 
/etc/init.d/unicorn upgrade. Then a dozen (full stack) checks are 
executed which must all pass before the app is considered to be up. 
Depending on the outcome of those checks an /etc/init.d/unicorn commit 
or rollback follows.



Cheers,
Lawrence


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Re: SIGWINCH

[Eric Wong]

Lawrence Pit <lawrence.pit@gmail.com> wrote:
> Hi,
>
> I followed the procedure to replace a running unicorn. Works fine,  
> except for one thing: after I decide to back out, ie I send a HUP to the  
> old master followed by a QUIT to the new master, then:

Ah, ok.  I can reproduce it.  The problem is the HUP by the old
master tries to reset the pid file to the non-"oldbin" version
which the new master is still holding on to.

You could QUIT the new master first and then HUP, but this is _far_ from
ideal because it leaves you with a window without running workers (and
also it contradicts our documentation).  It's also difficult to avoid
race conditions this way.

I'm looking for a better way to go about this, pid files are nasty :x

-- 
Eric Wong
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