Logging question/suggestion

[Eric Saunders]

Hi Kevin

What you describe sounds to me like a simple callback mechanism. I think 
it's a good idea. As you say, it allows the client to dynamically poll the 
logging-enabled service for status information, which may be important if 
the client wishes to initiate other jobs or services which are 
strongly dependent on the state of that service. However, I think it may 
still be a good idea to send an explicit confirmation message from the 
service if/when processing is complete, for example.

With regard to the 'UWS pattern' - as I understand it, this is simply an 
OO Factory pattern. Whether you choose to implement the logging service 
using a factory or through some other mechanism (e.g. a single collection 
or aggregate object representing the service) should make no difference to 
the external interface seen by the client. As far as the client is 
concerned, it makes a job request, receives a unique id which it uses to 
check on the status of the job... and that's all it knows, or cares.

Cheers

Eric

---------------------------------------
Eric Saunders
eSTAR Project (http://www.estar.org.uk)
Astrophysics Group
University of Exeter



On Thu, 25 May 2006, KevinBenson wrote:

> On the last day of the IVOA meeting me and Guy Rixon were chatting about the 
> Logging and namely how it will need to do e-mail and how users will check 
> e-mails to see when it is complete or if an error occurred.  And if your a 
> machine client you will need to monitor e-mail and/or VOSpace to see when 
> things are complete or error to do things more automated.  Also possibility 
> of e-mail systems being down even though rare could be a small/minor problem.
>
> A suggestion was made; how about implement the UWS pattern with Logging. 
> What do others think about it?
> It would mean that clients could do polling to see if a job is complete or 
> error happened, and possibly resume jobs if there was a problem.  It might 
> seem a little heavy weight, but since we agreed we need security, vospace, 
> handle long running queries, and a requestid which matches the resource 
> identifier it would seem UWS idea might be a good fit.  Plus it is quite 
> likely that libraries to handle UWS will incorporate the security and 
> vospace.
>
> cheers,
> Kevin
>