[Engine-devel] Serial Execution of Async Tasks

Allon Mureinik amureini at redhat.com
Wed Aug 22 09:21:23 UTC 2012 


----- Original Message -----
> From: "Maor Lipchuk" <mlipchuk at redhat.com>
> To: "Itamar Heim" <iheim at redhat.com>
> Cc: "Allon Mureinik" <amureini at redhat.com>, "engine-devel" <engine-devel at ovirt.org>, "Eduardo Warszawski"
> <ewarszaw at redhat.com>, "Yeela Kaplan" <ykaplan at redhat.com>, "Federico Simoncelli" <fsimonce at redhat.com>, "Liron
> Aravot" <laravot at redhat.com>
> Sent: Thursday, August 16, 2012 8:27:33 PM
> Subject: Re: [Engine-devel] Serial Execution of Async Tasks
> 
> On 08/16/2012 06:51 PM, Itamar Heim wrote:
> > On 08/16/2012 03:21 PM, Maor Lipchuk wrote:
> >> On 08/14/2012 05:23 PM, Itamar Heim wrote:
> >>> On 08/14/2012 02:35 PM, Maor Lipchuk wrote:
> >>>> How should we handle the auditLogMessages?
> >>>> Basically when a command ends it print an audit log.
> >>>>
> >>>> When we will start to use multiple tasks I assume user might get
> >>>> a bulk
> >>>> of audit logs which are actually related to the same action
> >>>> (when we
> >>>> fail for example the process will be create and delete).
> >>>> It might be a bit confusing for the user not to know which
> >>>> action is
> >>>> related to the operation
> >>>
> >>> I thought audit log gets written regardless of the transaction,
> >>> so audit
> >>> log appears "as they happen"?
> >> That is correct,
> >> The issue that I was referring to, is that now, with multiple
> >> tasks
> >> execution, we will get many audit logs which related to the same
> >> transaction but each one will be printed at a different time.
> >>
> >> I think that it might be confusing for the user to relate each
> >> audit log
> >> to the operation that was started.
> >>
> >>
> >> For example :
> >> User run an action that executes some tasks of create volumes,
> >> then the engine encounter a problem, and decide to rollback the
> >> operation and delete the volumes, in that case the engine will
> >> execute a
> >> delete task for the volumes, so user might see that delete of the
> >> volume
> >> (for example a snapshot) was initiated.
> >> Since those are asynchronous tasks, audit log will be printed in a
> >> different period of time and a user might not be aware what is the
> >> relation of those specific delete.
> > 
> > async doesn't mean we don't print an audit log when we start it,
> > and
> > when we end it.
> > so user would get the starting audit log when the task failed in
> > your
> > example. of course this may happen 2 hours after they started the
> > task.
> > as long as we can correlate the audit log to be part of the same
> > "job",
> > i don't see the issue.
> yes, but if I understood correctly, we don't want to correlate the
> multiple tasks with the execution handler (which AFAIK handle the
> correlation id).
I actually didn't mention this, but I don't see why not.
What's I'd probably like to have is a log with "Correlation ID xyzabc, step #3 starting/executing/ending"
Does this make any sense?
> 
> I assume this issue can be addressed in a future phase,
> but maybe it is an issue that might worth to think about.
> > 
> >>>
> >>>>
> >>>> Maybe we will need to use the correlation id of the Execution
> >>>> handler as
> >>>> Eli suggested or maybe add new states at CommandActionState?
> >>>>
> >>>> On 08/14/2012 02:10 PM, Allon Mureinik wrote:
> >>>>> Hi guys,
> >>>>>
> >>>>> Thanks for all your comments!
> >>>>> The correct response for many these points is to update the
> >>>>> wiki.
> >>>>> I'm enclosing here the quick-and-dirty replies just to keep
> >>>>> this
> >>>>> thread alive, and will update the wiki shortly.
> >>>>>
> >>>>> See inline.
> >>>>>
> >>>>> ----- Original Message -----
> >>>>>> From: "Livnat Peer" <lpeer at redhat.com>
> >>>>>> To: "Allon Mureinik" <amureini at redhat.com>
> >>>>>> Cc: "Eli Mesika" <emesika at redhat.com>, "Liron Aravot"
> >>>>>> <laravot at redhat.com>, "Federico Simoncelli"
> >>>>>> <fsimonce at redhat.com>, "engine-devel"
> >>>>>> <engine-devel at ovirt.org>,
> >>>>>> "Eduardo Warszawski" <ewarszaw at redhat.com>, "Yeela
> >>>>>> Kaplan" <ykaplan at redhat.com>
> >>>>>> Sent: Sunday, August 12, 2012 9:39:23 AM
> >>>>>> Subject: Re: [Engine-devel] Serial Execution of Async Tasks
> >>>>>>
> >>>>>> On 10/08/12 03:40, Eli Mesika wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> ----- Original Message -----
> >>>>>>>> From: "Allon Mureinik" <amureini at redhat.com>
> >>>>>>>> To: "engine-devel" <engine-devel at ovirt.org>
> >>>>>>>> Cc: "Eduardo Warszawski" <ewarszaw at redhat.com>, "Yeela
> >>>>>>>> Kaplan"
> >>>>>>>> <ykaplan at redhat.com>, "Federico Simoncelli"
> >>>>>>>> <fsimonce at redhat.com>, "Liron Aravot" <laravot at redhat.com>
> >>>>>>>> Sent: Thursday, August 9, 2012 6:41:09 PM
> >>>>>>>> Subject: [Engine-devel] Serial Execution of Async Tasks
> >>>>>>>>
> >>>>>>>> Hi guys,
> >>>>>>>>
> >>>>>>>> As you may know the engine currently has the ability to fire
> >>>>>>>> an
> >>>>>>>> SPM
> >>>>>>>> task, and be asynchronously be "woken-up" when it ends.
> >>>>>>>> This is great, but we found the for the Live Storage
> >>>>>>>> Migration
> >>>>>>>> feature we need something a bit complex - the ability to
> >>>>>>>> have a
> >>>>>>>> series of async tasks in a single control flow.
> >>>>>>>>
> >>>>>>>> Here's my initial design for this, your comments and
> >>>>>>>> criticism
> >>>>>>>> would
> >>>>>>>> be welcome:
> >>>>>>>> http://wiki.ovirt.org/wiki/Features/Serial_Execution_of_Asynchronous_Tasks_Detailed_Design
> >>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>> Apart from the short explanation & flow , since this is a
> >>>>>>> detailed
> >>>>>>> design , I would add
> >>>>>>> 1) Class diagram
> >>>>>>> 2) Flow diagram
> >>>>> Good idea, I'll see if I can jimmy something up.
> >>>>>
> >>>>>>>
> >>>>>>
> >>>>>> +1, it would help understanding the flow.
> >>>>>>
> >>>>>> - It looks like you chose not re-use/extend the
> >>>>>> ExecutionHandler (the
> >>>>>> entity used for building the tasks view exposed to the users).
> >>>>>> It might be a good idea to keep the separation between the
> >>>>>> engine
> >>>>>> Jobs
> >>>>>> and the underlying vdsm tasks, but I want to make sure you are
> >>>>>> familiar
> >>>>>> with this mechanism and ruled it out with a reason. If this is
> >>>>>> the
> >>>>>> case
> >>>>>> please share why you decided not to use it.
> >>>>> As you said Jobs and Steps are pure engine entities - they can
> >>>>> contain no VDSM tasks, one VDSM task, or plausibly, in the
> >>>>> future,
> >>>>> several tasks.
> >>>>> Even /today/, AsyncTasks and Jobs/Steps are two different kinds
> >>>>> of
> >>>>> animals - I don't see any added value in mixing them together.
> >>>>>
> >>>>>>
> >>>>>>
> >>>>>> - how does this design survives a jboss restart? Can you
> >>>>>> please a
> >>>>>> section in the wiki to explain that.
> >>>>> Basically, the way as a Command does today - the task is saved
> >>>>> with
> >>>>> the executionIndex, and continues when the command is woken up.
> >>>>> I'll clarify this point in the wiki.
> >>>>>
> >>>>>>
> >>>>>> -successful execution -
> >>>>>> * "CommandBase iterates over its SPMAsyncTaskHandlers" - when?
> >>>>> This is the new suggested format of executeCommand(). I'll
> >>>>> clarify
> >>>>> this too.
> >>>>>
> >>>>>> * If the second task is an HSM command (vs. SPM command), I
> >>>>>> think you
> >>>>>> should explain in the design how to handle such flows as well.
> >>>>> HSM commands do not create AsyncTasks, as they do today - I
> >>>>> will
> >>>>> clarify this.
> >>>>>
> >>>>>> * Why do we need before task? can you give a concrete example
> >>>>>> of what
> >>>>>> would you do in such a method.
> >>>>> Basically, /today/, command look like this:
> >>>>> executeCommand() {
> >>>>>     doStuffInTheDB();
> >>>>>     runVdsCommand(someCommand);
> >>>>> }
> >>>>>
> >>>>> endSuccessfully() {
> >>>>>     doMoreStuffInTheDB();
> >>>>> }
> >>>>>
> >>>>> endWithFailure() {
> >>>>>     doMoreStuffForFailureInTheDB();
> >>>>> }
> >>>>>
> >>>>> In the new design, the entire doStuffInTheDB() should be moved
> >>>>> to a
> >>>>> breforeTask of the (only) SPMAsyncTaskHandler.
> >>>>>
> >>>>>>
> >>>>>> - I see you added SPMAsyncTaskHandler, any reason not to use
> >>>>>> SPMAsyncTasK to manage it own life-cycle?
> >>>>> Conserving today's design - The SPMAsyncTaskHandler is the
> >>>>> place to
> >>>>> add additional, non-SPM, logic around the SPM task execution,
> >>>>> like
> >>>>> CommandBase allows today.
> >>>>>
> >>>>>>
> >>>>>> - In the life-cycle managed by the SPMAsyncTaskHandler there
> >>>>>> is a
> >>>>>> step
> >>>>>> 'createTask - how to create the async task' can you please
> >>>>>> elaborate
> >>>>>> what are the options.
> >>>>> new [any type of async task]
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> Livnat
> >>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> -Allon
> >>>>>>>> _______________________________________________
> >>>>>>>> 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
> >>>>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>> _______________________________________________
> >>>>> 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
> >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>>>
> >>>
> >>>
> >>
> >>
> > 
> > 
> 
> 
>

More information about the Devel mailing list