Savas Parastatidis wrote:

Dear all,
I think something needs to be clarified with regards to handling
multiple jobs with one message. The beauty of document-oriented
interactions is that you can do things like...
<job-details-request>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-001</job-id>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-010</job-id>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-002</job-id>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-029</job-id>
</job-details-request>
Or
<job-suspend-request>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-002</job-id>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-005</job-id>
  <job-id>urn:ogsa:job:guid:bla-bla-bla-008</job-id>
</job-suspend-request>
The schema for the above document can allow anything from 0 to N number
of <job-id> elements.

the trouble with any bulk operation is you have to handle partial failure. You need either atomic operations (not long lived transactions over HTTP Savas, I wouldn't be that daft), or a way of indicating that only a bit went wrong

Hence the 207 Multi-Status response in WebDav, the "something failed, look in the message". WebDav is still single instance (here a RESTy URL), but you can set >1 property and so have partial failure.

SOAP just has SOAPFault and extensions; no explicit multiple failure response. WS-RF-ResourceProperties has a similar problem with SetResourceProperties, but a different failure model in which any failure to set can result in a WS-BaseFault, indicating which failed, but providing no apparent information on which worked.

It seems to me that if you want to bulk stuff, you do need ways of (a) handling partial failure and (b) declaring what happens on partial failure. For the curions, WebDav's failure mode on file operations (MOVE, COPY) is explicitly declared to be that of failed file operations of Win98 on a FAT32 filesystem  [1,2]

Alternatively, you dont go for bulk operations, neither on a multiple jobs, or on multiple properties of a job (remember, WS-RF doesn't declare atomic/transacted property operations, so all you do here is increase the window of instability, a window that already exists). Instead you just stream a series of operations over the same HTTP1.1 connection -assuming that everything is accessible at the same far-end host, and get a series of (potentially out of order, we are talking HTTP1.1) responses.

This could be efficient, and you could do better handling of failure. But you do need a SOAP stack that can keep an HTTP1.1 channel open for multiple requests. Axis doesnt, even if you get httpclient to do the HTTP work; I don't know about .NET/WSE. You also need developers to model the communication correctly. Manipulating JAXRPC proxies as if they represent remote objects is *clearly* the wrong way to do it. You'd almost want to model a queue of requests waiting to be POSTed, a queue you can fill up then push out. Something like this, in your Java-era language of choice :-

//different queues for SOAP, REST
Queue q=new Soap12RequestQueue();

q.add(new StatePut(job1.uri,Job.LIFECYCLE,Job.SUSPENDED));
//let the queue reorder stuff if it wants to
q.add(new StatePut(job2.uri,Job.LIFECYCLE,Job.SUSPENDED),Queue.POSITION_OPTIMAL);
q.add(new StatePut(job3.uri,Job.LIFECYCLE,Job.SUSPENDED),Queue.POSITION_LAST);

q.setEventHandler(this);
q.nonBlockingSubmit();

No, there is no code behind this example, and I am avoiding any hints as to what the even handler would look like. I think the key point is that once you embrace remote operations as async actions, then you can model the manipulations differently.  Note also that I am representing job suspension not as an explicit suspend() operation, but as a request to put a job into the suspended state. This API could work with our friend REST just as easily as with WS-RF...

Anyway Savas, to conclude: do you have any evidence that a single document is suboptimal compared to a sequences of requests over an open HTTP/1.1 connection? That is, assuming we ignore the SHOULD in the HTTP1.1 specification " Clients SHOULD NOT pipeline requests using non-idempotent methods or non-idempotent sequences of methods" [3]

-Steve


[1] WebDav http://www.ietf.org/rfc/rfc2518.txt S8.9.2

"after encountering an error moving a non-collection
   resource as part of an infinite depth move, the server SHOULD try to
   finish as much of the original move operation as possible."

[2] http://lists.w3.org/Archives/Public/w3c-dist-auth/1997JulSep/0177.html

[3] RFC2616 HTTP1.1