Обсуждение: [GENERAL] delete a file everytime pg server starts/crashes

Hi, 

I'm having a requirement to delete a file in system whenever pg server is
started/crashed. Any idea?

Thanks,
Athi 



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That seems like an odd requirement and I don't think PostgreSQL can do 
it itself,
because if postgresql should crash properly then the process that should 
write/remove that file would also crash

The simplest way would be to write a cronjob that connects to the 
database and does a simple query to see if things are ok,
and act accordingly. But cronjobs cannot be executed more than once a 
miunute so there would be a considerable delay.

If you need faster responses you may need to write a custom deamon or 
use something like supervisord to manage a long polling script.

I get the feeling there must be a more elegant solution to whatever your 
problem is though...

On 2017-10-05 16:04, athinivas wrote:
> Hi,
> 
> I'm having a requirement to delete a file in system whenever pg server 
> is
> started/crashed. Any idea?
> 
> Thanks,
> Athi
> 
> 
> 
> --
> Sent from: 
> http://www.postgresql-archive.org/PostgreSQL-general-f1843780.html


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Look at inotify: https://github.com/rvoicilas/inotify-tools
You can check for instance if postmaster.pid exists.



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Actually if the name of the file doesn't matter you could put it into
$PGDATA/pg_stat and name it global.stat. When postgres stops (clean or
because of failure), replaces the file with his own. So your content will be
erased.
I'm not sure it's completely safe but works in simple test.



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Hi, 

Thank you...will try it :) ...As of now, I'm creating the filename as
pg_start_time so that, every time the server is up, a new file will be
created.


Regards,
Athi 



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Yes, will take the epoch value from same and create a new file. Upon
subsequent calls, will access with that filename...if it fails(incase if the
postmaster is restarted), will create a new one. 

@Melvin Does this capture all failure scenarios?? Or you have any other
better ways to do it. Your comments are much appreciated !!  



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