Re: [Qemu-devel] [PATCH v3] qemu-nbd: Implement socket activation.

["Richard W.M. Jones" <rjones@redhat.com>]

On Fri, Feb 03, 2017 at 09:31:43AM -0800, Paolo Bonzini wrote:
> 
> 
> On 03/02/2017 09:09, Richard W.M. Jones wrote:
> > +                                                   const char *port,
> > +                                                   bool fork_process)
> > +{
> > +    if (device != NULL) {
> > +        return "NBD device can't be set when using socket activation";
> > +    }
> > +
> > +    if (sockpath != NULL) {
> > +        return "Unix socket can't be set when using socket activation";
> > +    }
> > +
> > +    if (address != NULL) {
> > +        return "The interface can't be set when using socket activation";
> > +    }
> > +
> > +    if (port != NULL) {
> > +        return "TCP port number can't be set when using socket activation";
> > +    }
> > +
> > +    if (fork_process) {
> > +        return "Fork (--fork) can't be used with socket activation";
> > +    }
> 
> Why not?  You could have a Type=forking foo.service, which makes little
> sense but would work.

The answer, I think, is because systemd will lose track of the PID of
the qemu-nbd process.  This would be important because systemd can
kill a socket-activated service which is idle.

Normally you would work around that by using PIDFile=... in the unit
file, but it looks like qemu-nbd doesn't support pid files.

Rich.

> Apart from this, the patch seems fine.
> 
> > +    return NULL;
> > +}
> 
> 

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