[infinispan-dev] Command cancellation

[Vladimir Blagojevic]

Now that I am actually implementing this I am wondering why don't we 
simply add getUUID to CacheRpcCommand. CancellationService will use this 
UUID for command cancellation, some other services might need UUID for 
something else. Introducing CancellableCommand does not add much except 
bunch of instanceof constructs and explicitly connects UUID with concept 
of command cancellation which might not been only valid use of command UUID.


On 12-09-21 2:34 PM, Manik Surtani wrote:
> Looks good, except that the pseudocode for dealing with a 
> CancellableCommand (on the recipient node) should look like:
>
> * Receive command
> * if CancellableCommand, register with CancellationService
> * Perform command
> * If CancellableCommand, un-register from CancellationService
>
> That last step was missing from your detail below.  I presume that 
> would require a CancellationService#unregisterThread(UUID u) ?
>
> - Manik
>
> On 21 Sep 2012, at 11:42, Vladimir Blagojevic <vblagoje at redhat.com 
> <mailto:vblagoje at redhat.com>> wrote:
>
>> Hi,
>>
>> I wanted to run by you guys design of command cancellation Manik and I
>> talked about recently. For more background regarding this task read
>> https://issues.jboss.org/browse/ISPN-1042
>>
>> At originating node I would have each Cancellable command create its
>> UUID as part of constructor. After that command gets sent away to remote
>> VMs but just before it gets executed there we associated thread with
>> UUID by calling CancellationService.registerThread (as a first line of
>> code in Command#perform). After registration has been setup Cancellable
>> command goes into potentially lengthy (in seconds) execution. If needed
>> we would be able to send CancelCommand which would call
>> CancellationService#cancelTask with UUID. CancelTask would interrupt the
>> associated thread.
>>
>> WDYT?
>>
>> Regards,
>> Vladimir
>>
>> Cancellation of tasks:
>>
>> class CancellationService {
>>  UUID registerThread(Thread t, UUID uuid) {
>>     // put thread in map, associate with newly give UUID
>>    }
>>  void cancelTask(UUID uuid) {
>> //     look up thread, interrupt if exists.
>>   }
>> }
>>
>> interface CancellableCommand {
>>   UUID getCommandUUID();
>> }
>>
>> command CancelCommand {
>>   Object perform() {
>> //      Calls CancellationService.cancelTask with UUID.  The UUID is a
>> parameter of this command.
>>  }
>> }
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>
> --
> Manik Surtani
> manik at jboss.org <mailto:manik at jboss.org>
> twitter.com/maniksurtani <http://twitter.com/maniksurtani>
>
> Platform Architect, JBoss Data Grid
> http://red.ht/data-grid
>
>
>
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