[libvirt] [PATCH 10/21] Don't let parent of daemon exit until basic initialization is done

[Daniel Veillard]

On Thu, Oct 29, 2009 at 03:29:38PM +0000, Daniel P. Berrange wrote:
> On Thu, Oct 29, 2009 at 04:19:47PM +0100, Daniel Veillard wrote:
> > On Fri, Oct 23, 2009 at 02:05:39PM +0100, Daniel P. Berrange wrote:
> > > The daemonizing code lets the parent exit almost immediately. This
> > > means that it may think it has successfully started even when
> > > important failures occur like not being able to acquire the PID
> > > file. It also means network sockets are not yet open.
> > > 
> > > To address this when daemonizing the parent passes an open pipe
> > > file descriptor to the child. The child does its basic initialization
> > > and then writes a status code to the pipe indicating either success,
> > > or failure. This ensures that when daemonizing, the parent does not
> > > exit until the pidfile is acquired & basic network sockets are open.
> > > 
> > > Initialization of the libvirt drivers is still done asynchronously
> > > since this may take a very long time.
> > 
> >   Hum, on the other hand maybe it's still better to wait until having
> > gone though drivers inits, basically this affects boot time or service
> > (re) start time, but maybe it's better to give hand when the service is
> > actually started and ready to get connections. With the parallel boots
> > only services dependant on libvirt may have to wait a long time, and
> > maybe it's better that way.
> 
> We used to block on driver initialization, but its not really viable.
> It can take a *very* long time - many minutes if auto-starting lots
> of VMs.  
> 
> By initializing everything except the drivers, apps depending on 
> libvirt can reliably connect, but their RPC calls won't be processed
> until we finish driver init. So we effectively block dependant
> things, without impacting on the OS startup process

  okay then !

Daniel

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