[libvirt] [sandbox PATCH] allow to use a templated unit in virt-sandbox

[Michael Scherer]

Le vendredi 03 mai 2013 à 16:10 +0100, Daniel P. Berrange a écrit :
> On Fri, May 03, 2013 at 04:32:45PM +0200, Michael Scherer wrote:
> > This permit to create a templated unit inside the sandbox,
> > using the sandbox name as a variable and so running the same
> > unit with a different configuration without too much hassle.
> > 
> > For example, someone could have several different configuration of
> > website in /etc/nginx/websites.d/ and have each of them started in
> > a different sandbox, with a sample templated unit using the sandbox
> > name as a option to read the proper configuration file directly.
> > ---
> >  bin/virt-sandbox-service | 20 +++++++++++++++++---
> >  1 file changed, 17 insertions(+), 3 deletions(-)
> > 
> > diff --git a/bin/virt-sandbox-service b/bin/virt-sandbox-service
> > index 2096be1..0d89b54 100755
> > --- a/bin/virt-sandbox-service
> > +++ b/bin/virt-sandbox-service
> > @@ -345,6 +345,10 @@ class GenericContainer(Container):
> >      def set_command(self, command):
> >          self.config.set_command(command)
> >  
> > +
> > +def is_template_unit(unit):
> > +    return '@' in unit
> > +
> >  class SystemdContainer(Container):
> >      IGNORE_DIRS        = [ "/var/run/", "/etc/logrotate.d/", "/etc/pam.d" ]
> >      DEFAULT_DIRS       = [ "/etc", "/var" ]
> > @@ -624,14 +628,22 @@ WantedBy=%(TARGET)s
> >                  source = "%s%s" % ( self.dest, d)
> >                  self.add_bind_mount(source, d)
> >  
> > +    def get_expanded_unit_template(self, unit):
> > +        return unit.replace('@', '@' + self.name)
> > +
> >      def create_container_unit(self, src, dest, unit):
> > -            fd = open(dest + "/" + unit, "w")
> > -            fd.write(""".include %s
> > +            if is_template_unit(unit):
> > +                expanded_unit_name = self.get_expanded_unit_template(unit)
> > +                os.symlink(src, dest + "/" + expanded_unit_name)
> > +                shutil.copy(src, dest + "/" + unit)
> > +            else:
> > +                fd = open(dest + "/" + unit, "w")
> > +                fd.write(""".include %s
> >  [Service]
> >  PrivateTmp=false
> >  PrivateNetwork=false
> >  """ % src )
> > -            fd.close()
> > +                fd.close()
> 
> So originally we would create /etc/systemd/system/$NAME.service inside
> the container containing:
> 
>   .include /lib/systemd/system/$NAME.service
>   [Service]
>   PrivateTmp=false
>   PrivateNetwork=false
> 
> with your change, we're symlinking
> 
>  /etc/systemd/system/$NAME.service
> 
> to
> 
>  /lib/systemd/system/$UNITNAME at .service
> 
> 
> which means we loose the disablement of PrivateTmp and PrivateNetwork.
> Required because we're already in private namespaces & don't want to
> be creating more.
> 
> I think you need to create /etc/systemd/system/$UNITNAME at .service
> containing
> 
>   .include /lib/systemd/system/$UNITNAME at .service
>   [Service]
>   PrivateTmp=false
>   PrivateNetwork=false

But we are not sure of the location of the service file in the first
place, so we cannot include it like this.

And I want to be able to use it on custom unit sitting in /etc, as most
unit in /lib do not support templating ( my use case is "massive" vhost
hosting ).

What about using the system based
on /etc/systemd/system/$NAME.service.d/virt_sandbox.conf for config file
inclusion ?  ( didn't test yet )

Would it be a problem to depend on a recent enough systemd version for
this feature to work ?
( it is in since systemd 198, drop-in file support : 
http://lists.freedesktop.org/archives/systemd-devel/2013-March/009496.html )

-- 
Michael Scherer