----- Original Message -----
> From: "ybronhei" <ybron...@redhat.com>
> To: "Alon Bar-Lev" <alo...@redhat.com>
> Cc: "VDSM Project Development" <vdsm-devel@lists.fedorahosted.org>
> Sent: Sunday, December 30, 2012 2:28:45 PM
> Subject: Re: [vdsm] starting up vdsm and svdsm
> 
> On 12/30/2012 01:45 PM, Alon Bar-Lev wrote:
> >
> >
> > ----- Original Message -----
> >> From: "ybronhei" <ybron...@redhat.com>
> >> To: "Alon Bar-Lev" <alo...@redhat.com>
> >> Cc: "VDSM Project Development" <vdsm-devel@lists.fedorahosted.org>
> >> Sent: Sunday, December 30, 2012 1:40:03 PM
> >> Subject: Re: [vdsm] starting up vdsm and svdsm
> >>
> >> On 12/30/2012 12:11 PM, Alon Bar-Lev wrote:
> >>>
> >>>
> >>> ----- Original Message -----
> >>>> From: "ybronhei" <ybron...@redhat.com>
> >>>> To: "VDSM Project Development"
> >>>> <vdsm-devel@lists.fedorahosted.org>
> >>>> Sent: Sunday, December 30, 2012 11:53:17 AM
> >>>> Subject: [vdsm] starting up vdsm and svdsm
> >>>>
> >>>> Currently, vdsm deamon script starts (respawn) vdsm process as
> >>>> vdsm
> >>>> user, and during that vdsm starts super vdsm process as root.
> >>>>     * when vdsm dies, svdsm process supposed to notice and exit
> >>>>     by
> >>>>     itself.
> >>>>     * if svdsm dies, in the next proxy call by vdsm, vdsm
> >>>>     supposed
> >>>>     to
> >>>> start new svdsm instance after verifying that old instance is
> >>>> dead
> >>>> and
> >>>> call it.
> >>>> This is super vdsm and vdsm startup design in general.
> >>>> --
> >>>>
> >>>> In current implementation we have some edge cases that we need
> >>>> to
> >>>> handle:
> >>>>     * vsdm can try to communicate with old instance of svdsm.
> >>>>     * vdsm can kill wrong process that got last svdsm pid before
> >>>>     starting
> >>>> the new instance of svdsm.
> >>>>     * vdsm can try to communicate with svdsm before svdsm starts
> >>>>     to
> >>>>     serve
> >>>> requests.
> >>>> And i guess there are many more possible senerios that can cause
> >>>> bugs..
> >>>>
> >>>> As it seems, it doesn't make sense that vdsm manages root
> >>>> process,
> >>>> and
> >>>> can kill it..
> >>>>
> >>>> What if svdsm will be the manager of vdsm:
> >>>>     * deamon script starts up svdsm instance instead of vdsm
> >>>>     * svdsm forks vdsm and changes its privilege (uid to vdsm)
> >>>>     * vdsm receives as parameter svdsm pid for sudo requests
> >>>>     * when vdsm dies, svdsm will start new instance of vdsm
> >>>>     automatically,
> >>>> and note the crash reason to syslog.
> >>>>     * svdsm starts with respawn, so when svdsm dies, vdsm dies
> >>>>     also
> >>>>     as
> >>>>     its
> >>>> son process, and another instance of svdsm will start
> >>>> automatically
> >>>> and
> >>>> start new instance of vdsm.
> >>>>
> >>>> Sounds like much correcter and easier to maintain design.
> >>>
> >>> I am not sure I understand why these two services are related.
> >>>
> >>> As far as I understand svdsm is a total stateless slave without
> >>> any
> >>> logic, to provide privilege escalation to vdsm.
> >>> Why does it need to be restarted if vdsm changes state?
> >>> I expect it to exist as a separate service (init.d/systemd) and
> >>> vdsmd to depend on that service.
> >>>
> >>> What am I missing?
> >>>
> >> There is no relation between the states of the two. The only
> >> relation
> >> is
> >> that if one is up the other one must also be up and serve
> >> requests.
> >> for
> >> that case, systemd dependencies can solve the issue..
> >
> > This is a dependency.
> > Why "the other when must also be up?"
> >  From what I understand, there is no problem in having svdsm up
> >  anyway, hence no mutual dependency.
> > If we do have mutual dependency we should work to eliminate that
> > anyway.
> >
> right, svdsm can be up anyway.. but must be up and serve to let vdsm
> to
> be operational. and we can solve that by normal systemd dependency,
> as
> vdsm will require svdsm service and run it in type=forking (this way
> we
> guarantee that the parent exists and runs before starting).
> 
> I don't see any other mutual dependency between the two..
> 
> >> Instead of using systemd dependency and split the vdsmd service, I
> >> suggested to change the current relation and startup progress.
> >
> > Any benefit in that over using proper system services?
> >
> 
> Maybe not.. just need to consider differences between systemd and
> initctl (upstart) dependencies mechanism if we decide to rely on
> system
> services. And they work quite different..
> 
> If we don't want to have 2 implementations for that as we have now
> with
> some if-else statements in vdsmd.init script, it might help to keep
> it
> in one service that splits to 2 processes..

The problem is that we keep the same vdsmd.init for both...
Usually it is best to maintain the minimal script which is distribution 
dependent, and having it calling some common script.
For example if we port to debian, we probably need to do that anyway.
So best doing that earlier than later...

The init.d vdsmd script can start the svdsm and then call the common script, 
the systemd can just delegate calls. 

> 
> >> Separate
> >> to two services that depended on each-other is another option to
> >> consider.
> >>
> >>>>
> >>>> Also, svdsm can init whatever vdsm needs and is limited to do as
> >>>> a
> >>>> vdsm
> >>>> user (check log permissions, clean old temporary files and so on
> >>>> if
> >>>> needed..)
> >>>>
> >>>> Royce Lv has already started to work on such design here
> >>>> http://gerrit.ovirt.org/#/c/4145/
> >>>> I want to update it and push it forward.
> >>>>
> >>>> I would like to hear more opinions and point of views on this
> >>>> change,
> >>>>
> >>>> Thanks.
> >>>>
> >>>> --
> >>>> Yaniv Bronhaim.
> >>>> RedHat, Israel
> >>>> 09-7692289
> >>>> 054-7744187
> >>>> _______________________________________________
> >>>> vdsm-devel mailing list
> >>>> vdsm-devel@lists.fedorahosted.org
> >>>> https://lists.fedorahosted.org/mailman/listinfo/vdsm-devel
> >>>>
> >>
> >>
> >> --
> >> Yaniv Bronhaim.
> >> RedHat, Israel
> >> 09-7692289
> >> 054-7744187
> >>
> 
> 
> --
> Yaniv Bronhaim.
> RedHat, Israel
> 09-7692289
> 054-7744187
> 
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