On 18 March 2011 16:03, Andre Merzky
On Fri, Mar 18, 2011 at 4:02 PM,
wrote: Hi Andre
More changes made
Thanks, appreciated!
- the classes do not inherit the saga::async interface, and thus will not have asynchronous operations. Is that on purpose, or an oversight?
Again this is to remain consistent with the SD spec
Again, that point makes certainly sense, but may again point to an oversight in the SD spec. What is the rationale behind that decision? All other packages support remote operations, as it basically does not carry any ballast on implementation side (once you have implemented a way to do remote ops, its relatively easy to apply that to all calls), and async operations seem very useful in distributed applications?
I believe a the time it was considered that call to sd would be relatively fast. Do you have a use case for making use of sd in an asynchronous manner?
Latency issues are a general concern in distributed applications, and simply cannot be avoided. Just as an example: a project we work with does distributed runs over TeraGrid and DEISA. No matter how the app is configured, it needs to be able to cater for the cross atlantic latencies.
Now, I agree that most use cases of SD do not cover high-frequent queries - but IIUC, the ISN explicitely caters for browsing an arbitrary information service interactively - that, IMHO, immediately implies latency concerns.
Let me ask differently: what is the reason to *not* allow async ops? In general, that does not change the service interface, but allows the SAGA implementation to utilize threads for latency hiding. What is the downside?
It is only because we saw no benefit in adding the async complexity. If we add it to ISN then it really needs adding to SD as well. I will discuss the consequences directly with you in Taipei.
- You do not have TimeOut, PermissionDenied, Authorization/Authentication etc exceptions. I am unclear about the underlying protocol (and the API should not care), but are you sure those error modes do not (ever) apply to the calls?
- some calls have no exceptions whatsoever - are you sure they will *always* succeed? :-)
Added to constructor
get_data and list_related_entity_names the data has already been loaded and parsed as a result of the constructor so will always succeed
Well, you assume that your implementation fetches all data on the c'tor, and does no extra queries later on. But is that semantically prescribed by the API? I can't see that in the current spec - I think a stateless client could be implemented according to that API spec.
IFF you prescribe such a cache (and thus client state), what is it's scope, and its lifetime? Infinite may be a valid lifetime value I guess, but I doubt one would cache related entities of related entities?
By the nature of our implementation these make no sense but I accept that They may be relevant to other implementations
get_data() - added NoSucsess and Timeout exceptions list_related_entity_names() - added NoSucsess and Timeout exceptions
Yes, that is the point - I understand that your implementation may never throw those. Thanks.
exceptions Timeout to get_related_entities these calls should return objects that you are authorized to see
Are no race conditions possible between list_related_entity_names and get_related_entities (name)? Like, could an entry name returned by the first call disappear in the backend database before the second call gets called?
No, the entity names returned from list_related_entity_names are those defined in the glue schema, if they change then we need a new model
Ah, so an entry name being returned does not imply that data for that entry exist in the backend? I.e., if there is an optional element in the glue schema, and the database does not have a value for that element, that element's name is still returned in the list? That was not clear to me, thanks.
It would be very inefficient to look at the data to determine the set of related entities. This is just information from the schema. Steve
Best, Andre.
-- So much time, so little to do... [Garfield] -- saga-rg mailing list saga-rg@ogf.org http://www.ogf.org/mailman/listinfo/saga-rg