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From David Jencks <david_jen...@yahoo.com>
Subject Re: Spring integration...
Date Wed, 09 Feb 2005 00:33:44 GMT

On Feb 8, 2005, at 4:06 PM, Jules Gosnell wrote:

> Jeff Genender wrote:
>
>> I think Jules has a point on this.  What about the use of other open 
>> source projects that manage their own private mbean lifecycles, such 
>> as Tomcat?
>
>
> and not forgetting Jetty :-), which also exposes internals to JMX in 
> this way - relevant parts of which, I expect, implement the relevant 
> J2EE JSRs and would want to be made available to suitable tooling.

As far as I can tell jetty exposes some information via jmx but this 
has nothing to do with component lifecycle in jetty.

One problem with at least jetty's native lifecycle management is that 
it does not fit with the geronimo concept of separating the steps of 
processing the deployment descriptor xml into component configurations 
and actually starting the configurations in a possibly separate server. 
  For this and several other reasons I replaced jetty deployment 
descriptor processing and lifecycle management with a jetty-builder and 
gbeans for individual jetty components.  I anticipate that the same 
process will be needed for tomcat, and I was assuming a similar process 
would be used for Spring.  I haven't understood yet why this is a bad 
idea for Spring.
>
> If all goes well with a proxy approach, this fn-ality will go into the 
> Spring integration anyway, with a switch to disable it for the 
> faint-hearted. So, either way, the kernel will be managing POJOs whose 
> life-cycle it does not control. It's just a matter of how complex the 
> code has to be and how many levels of proxy we want...

I think one layer of proxy is plenty, but that 2 lifecycle managers is 
extremely unlikely to work.  IMO this requires a lot of careful 
thought.

thanks
david jencks

>
> Jules
>
>>
>> A significant portion of the Tomcat underbelly infrastructure is 
>> managed this way.
>>
>> In the debugconsole, I can see the Tomcat created mbean objects.  But 
>> when I try to manage them (view, etc), the debugconsole throws an 
>> Exception that the object is not a gbean.  I don't know of this is 
>> directly related, but it would be nice for gernimo to allow the 
>> plugged in components to manage thier own mbean lifecycles, and to be 
>> exposed.
>>
>> Jeff
>>
>>
>> Dain Sundstrom wrote:
>>
>>> I am definitely against this change.  A fundamental assumption of 
>>> the current GBean code is it controls life-cycle, and I believe 
>>> changing this would have a massive impact on the entire GBean 
>>> architecture.  I do believe that you could get it to work for your 
>>> small use case, but I believe that the impact will be much larger 
>>> then a small use case.  Further, I believe that you can use a 
>>> delegation model to achieve this today without a kernel patch.
>>>
>>> I'm not saying that this should never change, but that this is not 
>>> the time.  After certification, I would like to spend time 
>>> rethinking the GBean architecture.  Specifically, I'd like to make 
>>> it trivial to integrate Spring, Avalon, Pico, etc. components, and 
>>> I'd like to make it easier to program with GBeans.  This means, 
>>> taking a second look at the info object, data object, xml 
>>> configuration, persistence, dispatching and life-cycle.  Anyway, 
>>> this is something I believe can wait.
>>>
>>> -dain
>>>
>>>
>>> On Feb 8, 2005, at 1:55 AM, Jules Gosnell wrote:
>>>
>>>> So, Guys,
>>>>
>>>> I've given you a few days to look over the minimal kernel patch.
>>>>
>>>> As I understood it we left the thread with two real options :
>>>>
>>>> 1) extend the kernel to allow acceptance of an existing object for 
>>>> proxying via GBeanInstance, rather than always constructing such 
>>>> objects itself.
>>>>
>>>> 2) submit a dynamically crafted class and required instance (as 
>>>> constructor arg for said class). when class is instantiated and 
>>>> injected result will be a proxy that is [largely] semantically 
>>>> identical to (1). We must be able to proxy non-interfaces and final 
>>>> methods.
>>>>
>>>> To summarise the debate over the two options :
>>>>
>>>> against (1), for (2)
>>>> understandable reticence to change the kernel
>>>> concern over the kernel losing explicit ownership of the life-cycle 
>>>> of the object that it is managing
>>>>
>>>> for (1), against (2)
>>>> we are talking about an extension, not a backwardly incompatible 
>>>> change to the kernel
>>>> I have demonstrated that such an extension would have minimal 
>>>> footprint and implication
>>>> (2) does not restore lifecycle ownership to the kernel
>>>> (2) is complex, less efficient and will need to be repeated 
>>>> anywhere someone needs this fn-ality
>>>> (1) is simpler, more efficient and will only need to be done once
>>>>
>>>> Finding a resolution to this is, IMHO, critical to the Spring 
>>>> integration. Otherwise I would let it go.
>>>>
>>>> I had a very similar problem integrating two other well known 
>>>> pieces of open source some time ago. The host had a JMX kernel and 
>>>> the thing that I was embedding had internal MBeans with their own 
>>>> private lifecycles. I persuaded the powers-that-were to allow 
>>>> MBeans that were not managed by the kernel to be exposed via it. A 
>>>> change was made. The extension to the kernel was never rescinded. 
>>>> In fact, at least one other integration now makes use of it. It 
>>>> enabled embedded components to open themselves up to the services 
>>>> supplied by the kernel in a way that could not be done before...
>>>>
>>>> I humbly await your judgement :-)
>>>>
>>>>
>>>> Jules
>>>>
>>>>
>>>>
>>>> -- 
>>>> "Open Source is a self-assembling organism. You dangle a piece of
>>>> string into a super-saturated solution and a whole operating-system
>>>> crystallises out around it."
>>>>
>>>> /**********************************
>>>> * Jules Gosnell
>>>> * Partner
>>>> * Core Developers Network (Europe)
>>>> *
>>>> *    www.coredevelopers.net
>>>> *
>>>> * Open Source Training & Support.
>>>> **********************************/
>>>
>>
>
>
> -- 
> "Open Source is a self-assembling organism. You dangle a piece of
> string into a super-saturated solution and a whole operating-system
> crystallises out around it."
>
> /**********************************
> * Jules Gosnell
> * Partner
> * Core Developers Network (Europe)
> *
> *    www.coredevelopers.net
> *
> * Open Source Training & Support.
> **********************************/
>


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