Re: [Engine-devel] Serial Execution of Async Tasks

>>>>>>>>> Hi guys, >>>>>>>>> >>>>>>>>> As you may know the engine currently has the ability to fire >>>>>>>>> an >>>>>>>>> SPM >>>>>>>>> task, and be asynchronously be "woken-up" when it ends. >>>>>>>>> This is great, but we found the for the Live Storage >>>>>>>>> Migration >>>>>>>>> feature we need something a bit complex - the ability to >>>>>>>>> have a >>>>>>>>> series of async tasks in a single control flow. >>>>>>>>> >>>>>>>>> Here's my initial design for this, your comments and >>>>>>>>> criticism >>>>>>>>> would >>>>>>>>> be welcome: >>>>>>>>> http://wiki.ovirt.org/wiki/Features/Serial_Execution_of_Asynchronous_Task... >>>>>>> -successful execution - >>>>>>> * "CommandBase iterates over its SPMAsyncTaskHandlers" - when? >>>>>> This is the new suggested format of executeCommand(). I'll >>>>>> clarify >>>>>> this too. >>>>>> >>>>>>> * If the second task is an HSM command (vs. SPM command), I >>>>>>> think you >>>>>>> should explain in the design how to handle such flows as well. >>>>>> HSM commands do not create AsyncTasks, as they do today - I >>>>>> will >>>>>> clarify this. >>>>>> >>>>>>> * Why do we need before task? can you give a concrete example >>>>>>> of what >>>>>>> would you do in such a method. >>>>>> Basically, /today/, command look like this: >>>>>> executeCommand() { >>>>>> doStuffInTheDB(); >>>>>> runVdsCommand(someCommand); >>>>>> } >>>>>> >>>>>> endSuccessfully() { >>>>>> doMoreStuffInTheDB(); >>>>>> } >>>>>> >>>>>> endWithFailure() { >>>>>> doMoreStuffForFailureInTheDB(); >>>>>> } >>>>>> >>>>>> In the new design, the entire doStuffInTheDB() should be moved >>>>>> to a >>>>>> breforeTask of the (only) SPMAsyncTaskHandler. >>>>>> >>>>>>> >>>>>>> - I see you added SPMAsyncTaskHandler, any reason not to use >>>>>>> SPMAsyncTasK to manage it own life-cycle? >>>>>> Conserving today's design - The SPMAsyncTaskHandler is the >>>>>> place to >>>>>> add additional, non-SPM, logic around the SPM task execution, >>>>>> like >>>>>> CommandBase allows today. >>>>>> >>>>>>> >>>>>>> - In the life-cycle managed by the SPMAsyncTaskHandler there >>>>>>> is a >>>>>>> step >>>>>>> 'createTask - how to create the async task' can you please >>>>>>> elaborate >>>>>>> what are the options. >>>>>> new [any type of async task]