> On Nov 26, 2014, at 11:51 AM, Ira McDonald <blueroofmusic at gmail.com> wrote:
>> Hi Mike,
>> For operation (3) DeregisterOutputDevice, I was thinking of the case
> where a running service (Print in the near term) crashes (and this is
> noticed by System Service, let us hope). If DeregisterOutputDevice
> is (redundantly) supported by the System Service, then an Administrator
> could do the cleanup for the Infrastructure Printer (who might queue
Presumably DeregisterSystem is the way for the System service to clean up references to the output device in all services it manages, even those that have "crashed" (which is a state we don't really model semantically...) If you want to deregister from a single service, you talk to that one service.
> Or, I'm crazy, and the System Service would automatically do this
> cleanup internally and no external operation needs to be exposed.
> But that risks a Deregister when the crashed service can be
> successfully automatically restarted by the System Service after
> a brief interval of unavailability.
I would assume that self-healing of this sort would be expected of a cloud/SDN solution, with notifications sent to the relevant admin/operator. And I don't think we can necessarily recover from all situations like this - the Proxy might well have gotten a response from its Deregister-Output-Device request, with the cloud service crashing after successfully sending a response, so we have to hope that implementations will provide a way to perform manual cleanup as needed...
> I have mixed feelings about the reliability (and advisability) of
> automatic recovery by the System Service for crashed or stalled
> Job Services.
Typically servers will be restarted a certain number of times in order to provide continuous service, with an alert going out for each crash/failed restart. And such things are typically configurable by service and various events - I have such things setup with our PWG.org <http://pwg.org/> server instance, for example...
Michael Sweet, Senior Printing System Engineer, PWG Chair
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