Master process on reload

[B.R.]

Thanks Maxim!
Helpful and concise as always. :o)
---
*B. R.*

On Wed, Jun 29, 2016 at 7:38 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:

> Hello!
>
> On Wed, Jun 29, 2016 at 07:04:48PM +0200, B.R. wrote:
>
> > Kind of basic question about nginx behavior here.
> >
> > On the docs page http://nginx.org/en/docs/control.html, it is said :
> >
> > > HUP -> changing configuration, keeping up with a changed time zone
> (only
> > > for FreeBSD and Linux), starting new worker processes with a new
> > > configuration, graceful shutdown of old worker processes
> >
> > This is exact since the HUP signal is used to reload configuration and
> > spawn new workers with it.
> >
> > However, a little bit further on the same page, in the on-the-fly upgrade
> > section, you got:
> >
> > > Send the HUP signal to the old master process. The old master process
> will
> > > start new worker processes without re-reading the configuration. After
> > > that, all new processes can be shut down gracefully, by sending the
> QUIT
> > > signal to the new master process.
> >
> > Is this behavior due to the USR2 signal previously sent, the old master
> > knowing it is the old one (and thus knowing it should avoid loading an
> > improper configuration suitable for another version)?
>
> Yes.  The old master knows it previously started a new master,
> and on the HUP signal it just starts new workers (if the new
> master is still running).  If/when the old master exits, the old
> master is notified about this, and starts to work normally.
>
> Additional details can be found in
> src/os/unix/ngx_process_cycle.c:
>
> http://hg.nginx.org/nginx/file/tip/src/os/unix/ngx_process_cycle.c#l220
>
> --
> Maxim Dounin
> http://nginx.org/
>
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>
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