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From Saminda Wijeratne <samin...@gmail.com>
Subject Orchestration Component implementation review
Date Fri, 17 Jan 2014 15:32:49 GMT
Following are few thoughts I had during my review of the component,

*Multi-threaded vs single threaded*
If we are going to have multi-threaded job submission the implementation
should work on handling race conditions. Essentially JobSubmitter should be
able to "lock" an experiment request before continuing processing that
request so that other JobSubmitters accessing the experiment requests a the
same time would skip it.

*Orchestrator service*
We might want to think of the possibility in future where we will be having
multiple deployments of an Airavata service. This could particularly be
true for SciGaP. We may have to think how some of the internal data
structures/SPIs should be updated to accomodate such requirements in future.

*Orchestrator Component configurations*
I see alot of places where the orchestrator can have configurations. I
think its too early finalize them, but I think we can start refactoring
them out perhaps to the airavata-server.properties. I'm also seeing the
orchestrator is now hardcoded to use default/admin gateway and username. I
think it should come from the request itself.

*Visibility of API functions*
I think initialize(), shutdown() and startJobSubmitter() functions should
not be part of the API because I don't see a scenario where the gateway
developer would be responsible for using them. They serve a more internal
purpose of managing the orchestrator component IMO. As Amila pointed out so
long ago (wink) functions that do not concern outside parties should not be
used as part of the API.

*Return values of Orchestrator API*
IMO unless it is specifically required to do so I think the functions does
not necessarily need to return anything other than throw exceptions when
needed. For example the launchExperiment can simply return void if all is
succesful and return an exception if something fails. Handling issues with
a try catch is not only simpler but also the explanations are readily
available for the user.

*Data persisted in registry*
ExperimentRequest.getUsername() : I think we should clarify what this
username denotes. In current API, in experiment submission we consider two
types of users. Submission user (the user who submits the experiment to the
Airavata Server - this is inferred by the request itself) and the execution
user (the user who corelates to the application executions of the gateway -
thus this user can be a different user for different gateway, eg: community
user, gateway user).
I think we should persist the date/time of the experiment request as well.
Also when retrying of API functions in the case of a failure in an previous
attempt there should be a way to not to repeat already performed steps or
gracefully roleback and redo those required steps as necessary. While such
actions could be transparent to the user sometimes it might make sense to
allow user to be notified of success/failure of a retry. However this might
mean keeping additional records at the registry level.

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