[Engine-devel] [backend] a little confusion about the quartz jobs

[Laszlo Hornyak]

----- Original Message -----
> From: "Yair Zaslavsky" <yzaslavs at redhat.com>
> To: "Laszlo Hornyak" <lhornyak at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Thursday, February 23, 2012 1:31:03 PM
> Subject: Re: [Engine-devel] [backend] a little confusion about the quartz jobs
> 
> On 02/14/2012 06:49 PM, Laszlo Hornyak wrote:
> > 
> > 
> > ----- Original Message -----
> >> From: "Yair Zaslavsky" <yzaslavs at redhat.com>
> >> To: engine-devel at ovirt.org
> >> Sent: Tuesday, February 14, 2012 2:01:41 PM
> >> Subject: Re: [Engine-devel] [backend] a little confusion about the
> >> quartz jobs
> >>
> >> On 02/14/2012 02:21 PM, Mike Kolesnik wrote:
> >>>> hi,
> >>>>
> >>>> I was playing with the quartz jobs in the backend and I thought
> >>>> this
> >>>> is an area where some simplification and/or cleanup would be
> >>>> useful.
> >>>>
> >>>>  - SchedulerUtil interface would be nice to hide quartz from the
> >>>>  rest
> >>>>  of the code, but it very rarely used, the clients are bound to
> >>>>  it's
> >>>>  single implementation, SchedulerUtilQuartzImpl through it's
> >>>>  getInstance() method.
> >>>
> >>> I think the whole class name is misleading, since usually when I
> >>> imagine a utils class, it's a simple class that does some menial
> >>> work for me in static methods, and not really calls anything else
> >>> or even has an instance.
> >> +1
> > 
> > Agreed, I will rename it.
> > 
> >>>
> >>> Maybe the class can be renamed to just Scheduler, or
> >>> ScheduleManager which will be more precise.
> >>>
> >>>>  - It was designed to be a local EJB, Backend actually expects
> >>>>  it
> >>>>  to
> >>>>  be injected. (this field is not used)
> >>>>  - when scheduling a job, you call schedule...Job(Object
> >>>>  instance,
> >>>>  String methodName, ...) however, it is not the _methodname_
> >>>>  that
> >>>>  the executor will look for
> >>>>  - instead, it will check the OnTimerMethodAnnotation on all the
> >>>>  methods. But this annotation has everywhere the methodName as
> >>>>  value
> >>>>  - JobWrapper actually iterates over all the methods to find the
> >>>>  one
> >>>>  with the right annotation
> >>>>
> >>>> So a quick simplification could be:
> >>>>  - The annotation is not needed, it could be removed
> >>>>  - JobWrapper could just getMethod(methodName, argClasses)
> >>>>  instead
> >>>>  of
> >>>>  looking for the annotation in all of the methods
> >>>
> >>> Sounds good, or maybe just keep the annotation and not the method
> >>> name in the call/annotation since then if the method name changes
> >>> it won't break and we can easily locate all jobs by searching for
> >>> the annotation..
> This is why the annotations were introduced in the first place, we
> have
> too much places in code where we rely on usage of strings and
> reflection
> , so if a method name gets changed, the code stops working after
> being
> compiled.
> As this is the case, we should consider sticking to @OnTimer
> annotation,
> but maybe a proper documentation on the motivation for it should be
> added.

I understand your decision but...
 - the methods are usually about 5-10 lines below the schedule.*Job call, it is very hard not to notice the connection
 - for safe and easy refactoring, it could be better to pass over a callback
 - plus in the schedule.*Job call it could then be better to check if such method still exists, should throw an IllegalArgumentException if not there in this case we could catch the problem right at the cause, not when scheduled

> 
> >>>
> >>>>  - I am really not for factoryes, but if we want to separate the
> >>>>  interface from the implementation, then probably a
> >>>>  SchedulerUtilFactory could help here. The dummy implementation
> >>>>  would do just the very same thing as the
> >>>>  SchedulerUtilQuartzImpl.getInstance()
> >>>>  - I would remove the reference to SchedulerUtil from Backend as
> >>>>  well, since it is not used. Really _should_ the Backend class
> >>>>  do
> >>>>  any scheduling?
> >>>
> >>> Backend does schedule at least one job in it's Initialize()
> >>> method..
> >> Yes, we have the DbUsers cache manager that performs periodic
> >> checks
> >> for
> >> db users against AD/IPA.
> >> This scheduler should start upon @PostConstruct (or any logical
> >> equivalent).
> >>
> > 
> > Yes but I am not sure this should happen right there. All the other
> > service installs it's own jobs, so maybe SessionDataContainer
> > should do so as well. It would look more consistent.
> > 
> >>> Maybe the class should be injected, but I don't know if that
> >>> happens so maybe that's why it's unused.
> >>>
> >>>>
> >>>> Please share your thoughts.
> >>>>
> >>>> Thank you,
> >>>> Laszlo
> >>>> _______________________________________________
> >>>> Engine-devel mailing list
> >>>> Engine-devel at ovirt.org
> >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>>>
> >>> _______________________________________________
> >>> Engine-devel mailing list
> >>> Engine-devel at ovirt.org
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> >>
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> 
>