We have access to all configuration parameters in the context of api.py. May be 
you don't pass it but just instantiate it where you need it? Or I may 
misunderstand what you're trying to do...

DZ> 

PS: can you generate and update mistral.config.example to include new oslo 
messaging options? I forgot to mention it on review on time. 


On Mar 13, 2014, at 11:15 AM, W Chan <[email protected]> wrote:

> On the transport variable, the problem I see isn't with passing the variable 
> to the engine and executor.  It's passing the transport into the API layer.  
> The API layer is a pecan app and I currently don't see a way where the 
> transport variable can be passed to it directly.  I'm looking at 
> https://github.com/stackforge/mistral/blob/master/mistral/cmd/api.py#L50 and 
> https://github.com/stackforge/mistral/blob/master/mistral/api/app.py#L44.  Do 
> you have any suggestion?  Thanks. 
> 
> 
> On Thu, Mar 13, 2014 at 1:30 AM, Renat Akhmerov <[email protected]> 
> wrote:
> 
> On 13 Mar 2014, at 10:40, W Chan <[email protected]> wrote:
> 
>> I can write a method in base test to start local executor.  I will do that 
>> as a separate bp.  
> Ok.
> 
>> After the engine is made standalone, the API will communicate to the engine 
>> and the engine to the executor via the oslo.messaging transport.  This means 
>> that for the "local" option, we need to start all three components (API, 
>> engine, and executor) on the same process.  If the long term goal as you 
>> stated above is to use separate launchers for these components, this means 
>> that the API launcher needs to duplicate all the logic to launch the engine 
>> and the executor. Hence, my proposal here is to move the logic to launch the 
>> components into a common module and either have a single generic launch 
>> script that launch specific components based on the CLI options or have 
>> separate launch scripts that reference the appropriate launch function from 
>> the common module.
> 
> Ok, I see your point. Then I would suggest we have one script which we could 
> use to run all the components (any subset of of them). So for those 
> components we specified when launching the script we use this local 
> transport. Btw, scheduler eventually should become a standalone component 
> too, so we have 4 components.
> 
>> The RPC client/server in oslo.messaging do not determine the transport.  The 
>> transport is determine via oslo.config and then given explicitly to the RPC 
>> client/server.  
>> https://github.com/stackforge/mistral/blob/master/mistral/engine/scalable/engine.py#L31
>>  and 
>> https://github.com/stackforge/mistral/blob/master/mistral/cmd/task_executor.py#L63
>>  are examples for the client and server respectively.  The in process Queue 
>> is instantiated within this transport object from the fake driver.  For the 
>> "local" option, all three components need to share the same transport in 
>> order to have the Queue in scope. Thus, we will need some method to have 
>> this transport object visible to all three components and hence my proposal 
>> to use a global variable and a factory method. 
> I’m still not sure I follow your point here.. Looking at the links you 
> provided I see this:
> 
> transport = messaging.get_transport(cfg.CONF)
> 
> So my point here is we can make this call once in the launching script and 
> pass it to engine/executor (and now API too if we want it to be launched by 
> the same script). Of course, we’ll have to change the way how we initialize 
> these components, but I believe we can do it. So it’s just a dependency 
> injection. And in this case we wouldn’t need to use a global variable. Am I 
> still missing something?
> 
> 
> Renat Akhmerov
> @ Mirantis Inc.
> 
> 
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