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From "Hubert, Eric" <Eric.Hub...@foxmobile.com>
Subject RE: startup order - correct place to start transport listeners
Date Fri, 10 Apr 2009 12:53:24 GMT
Sorry for the late reply, I’ve been very busy this week. Please see my comments inline!

 

The steps you have listed are correct and please note that the ServerManager has been now
instrumented with the following sequence of life cycle methods and I have realized that at
least for now we do not need this same method structure on the ManagedLifecycle interface.

ServerManager#init()
ServerManager#start()
ServerManager#stop()
ServerManager#destroy()

If you look for the state transition it is as shown in this diagram.



Thanks for creating this diagram which illustrates all the states and their particular intend.
Maybe this can be included in some developer documentation?

 

	1)       Who shall call destroy() on ServerManager? (Only the shutdown hook defined in SynapseServer
after calling stop()?) Or was it originally meant that destroy is called instead of stop()?

Well stop and destroy are two operations, once you stop you may again start the server without
initializing the server, where as if you call destroy the server has to be reinitialized to
start. In contrast if you call destroy while the state is being ServerState.STARTED we first
stop the server and then destroy it.

 

Yes, the state diagram already explained this. So calling just destroy() in the shutdown hook
would have the same effect as destroy() checks the current state first and then calls the
appropriate methods to do the proper transition(s). In case the server is started, it first
calls stop() and then calls doDestroy(). Maybe this was a bit confusing me. 

On the other hand I asked myself, why SynapseStartupServlet calls ServerManager.stop() and
not ServerManager.destroy() in its destroy() method. If I understand it correctly this Servlet
is only used for the deployment option where Synapse runs inside a web container as a web
application (WAR). For this case Synapse is initialized and destroyed via this servlet. But
shouldn’t the server not only but stopped but rather completely destroyed? Who else should
take care of calling ServerManager.destroy()?

	2)       Why is destroy public? Why does stop() not call doDestroy() directly? Answer to
1) may already answer this.

I think the answer above explains why I did it like this. Even though from the code that we
have right now it seem like we could merge these two, in order to properly manage the states
and keeping the room for any extensibility on the shutdown process, I implemented it like
this. If you look at the shutdown process now, it is the exact opposite of the start order
which has to be the case. 

Well not the exact opposite order as discussed later… ;-)

 

	3)       What is the relation of the task_scheduler and synapse.startup.taskscheduler (TaskConstants/SynapseConstants)?
So far I had no contact with tasks at all. I’m only a bit confused about to places where
some schedulers are going to be destroyed: Axis2SynapseController.cleanupDefault() and SynapseConfiguration.destroy()

Good point, there seems to be some further improvements to the task scheduling logic... the
references that you pointed does the same and we should get rid of one. I think it has to
be the cleanupDefaults keeping the destroying process in the SynapseConfig#destroy 

+1

	Regarding the shutdown order I’m still not quite sure whether it is entirely correct. The
position of start and stop of listeners seems to be correct, though. I’m wondering why SynapseConfiguration.destroy()
is called rather late. I would have expected it to be called even before Axis2SynapseController.destroySynapseEnvironment(),
but I have had no time to think about the reasoning.

We could change the order of these two. 

+1

	Maybe you concentrated on the startup and did only some changes to the shutdown process.
I will be able to take more than just a few minutes at the weekend. I just wanted to give
a quick feedback on your efforts which are highly appreciated.

	Thanks, I think apart from the above swap it is OK, I highly concentrated on the shutdown
order as well, and even had to get the Axis2 Listener Manager fixed to support this scenario.
	Yes, I have noticed the Axis2 changes and updated it locally at the time the changes were
not available. Thanks for keeping us updated about your changes. This way it is much easier
to follow changes. 

	Thanks,
	    Eric

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