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From Jan Bartel <>
Subject Re: -1 on checkin of 368344 was Re: [wadi-dev] Clustering: WADI/Geronimo integrations.
Date Sun, 15 Jan 2006 20:26:14 GMT

To paraphrase what you said (if I understand correctly), the choices are 
to either back clustering out of geronimo for the 1.0.1 release and work on it 
for a future release, or to make minimal changes to it to make it work
in geronimo as is.

I think it's unlikely that there will be a significant rush to production 
with a 1.0 release of geronimo, so there is probably a bit of latitude 
for less-than-optimal functioning in terms of 2nd order functionality 
such as clustering if it were to be left in. It would be good to get 
Jules' input on the state of WADI on this point.

However, if we leave clustering in the way it is implemented at the moment, 
then the disadvantages are:
1. clustering is enabled differently for tomcat and jetty and a basic
   tenet of geronimo is to make the webcontainers interchangeable
2. clustering is enabled in the webapp descriptors instead of the container
3. users that use the 1.0.1 clustering will have to change each webapp
   to use it on future releases. 

If we roll forward again to the most recent clustering changes:
1. clustering interface is uniform for both tomcat and jetty
2. clustering is enabled in the container 
3. no geronimo webapp descriptor changes necessary

Of course, the most recent changes are not the final clustering
solution, so there would be changes to the container plans
in the future (eg in 1.1). But changes to the plans could probably 
be expected for any geronimo services between releases, no?

I don't like the option of leaving the clustering with per-webapp
geronimo descriptor configuration because it's just simply the
wrong way to do it and will be a pain in the neck for users when
we change to a better way in future releases. I think it would be 
better to take clustering out than to release 1.0.1 with it like it is.

So, the two options I see for 1.0.1 are:

1. take the clustering out and release in 1.1 after more discussion
2. leave clustering in, roll forward again and fix any issues

I really don't have a preference either way - I think both are 


> I think that it would be better to work on clustering in head and not  
> try to hurry to get something that we know will change and has not  been 
> well tested into 1.0.1.  I have no experience with actual  clustering.  
> Will people who want to use it expect something well  tested and 
> stable?  Will they be willing to work off snapshot builds  to pick up 
> the latest fixes?  What would the reaction be to something  that only 
> sort of works in an official release?
> thanks
> david jencks
> On Jan 14, 2006, at 3:46 AM, Jules Gosnell wrote:
>> OK, Folks - here is how I see it -
>> Everyone knows that they are right and the other guy is wrong.
>> Result - DEADLOCK - everyone loses.
>> Solution - release locks, back off, coordinate, retry.
>> Releasing locks involves us all making concessions :
>> I suggest -
>> Jan, Greg and I conceded that Jeff could have been more involved in  
>> discussion before this change went in.
>> Jeff concedes that Jan, Greg and I should have been involved in  
>> discussion before he backed the change out.
>> We all agree to overlook all current technical differences.
>> We all agree to put aside whatever bad feelings may have arisen  from 
>> this incident.
>> OK - locks released, backing-off complete.
>> Now, coordination :
>> WADI side :
>> I will downgrade the to a log.debug
>> I will remove the axion dependency.
>> I will resubmit the change as a patch to Jan and Jeff.
>> Jetty/Tomcat side :
>> Jan and Jeff will take this patch, and all relevant input.
>> If they feel that they need further discussion, they will have it.
>> They will implement a simple, unified solution to the issue for all  
>> existing cases and get it in to Geronimo 1.0.1
>> I simply want a speedy, painless resolution so we can continue  forward.
>> If everyone else is happy with these terms, then here is my '+1'
>> Jules
>> Jeff Genender wrote:
>>> Hi Jules.
>>> A few comments.  First, you made changes without discussing them  on the
>>> dev lists.
>>> As per the discussions in the past, both Aaron and David Jencks,  as 
>>> well
>>> as I threw in our .02 on how to integrate the clustering.  I would
>>> appreciate you discuss code ideas and changes that have such a  drastic
>>> impact on the Geronimo code base.  Here are the issues with your  
>>> check in:
>>> 1) I explained before for Jetty, and obviously now I need to do it  for
>>> Tomcat, a -1 on Axion as a dependency.  There should not be any web
>>> application dependencies injected at the container level.  This means
>>> there is a severe architectural issue with WADI when we are injecting
>>> these dependencies into the container.
>>> 2) You hard coded in org.codehaus.wadi.tomcat55.TomcatManager as the
>>> distributablesession manager in the TomcatContainer.  Hardcoding a
>>> pluggable session engine is very bad, and defeats the pluggability  of a
>>> configuration that we requested.
>>> 3) You placed in the code, and Aaron worked pretty hard to
>>> clean those up.
>>> 4) Your integration of setting the manager (no matter what) is a  direct
>>> clash with the
>>> Jules, I am giving a complete -1 of checkin of 368344.  These are all
>>> for technical reasons.  Please back out these changes, and bring this
>>> discussion to the Geronimo lists as this needs some significant
>>> discussion for implementation.  I would appreciate that you please
>>> involve the Apache way and open discussions on the lists before doing
>>> this sort of thing in the future.
>>> Again, I will CC the G lists to make this clear, that I would like  this
>>> change backed out.
>>> Jeff
>>> Jules Gosnell wrote:
>>>> Here is a list of outstanding issues associated with this work:
>>>> - ActiveMQ's shutdown hook seems to trigger when Geronimo is  shutdown,
>>>> removing AMQ before WADI - WADI doesn't like this. I have added a
>>>> property to the script which suppresses this behaviour. I  will
>>>> document it in the Getting Started doc.
>>>> - There 'may' be issues with nodes finding each other, when a  Geronimo
>>>> node is introduced into a WADI cluster - investigating.
>>>> - Jeff - you should look over the changes and make sure that they  
>>>> do not
>>>> impact on any other TC fn-ality. They were done with Emacs, so the
>>>> formatting may be offensive. Please feel free to make them your  own 
>>>> and
>>>> bring any issues back to the list. The WADIGBean, is no longer  
>>>> used, so
>>>> you may want to remove this from the repo.
>>>> - Jan and Jeff - since this config is now done on the container  
>>>> bean and
>>>> not in the geronimo-web.xml, you may no longer need to implement  your
>>>> own geronimo-web.xml schemas (I haven't looked very closely at  TC). 
>>>> You
>>>> may want to consider this and perhaps lose them.
>>>> - In order to get the same webapp to work in all containers
>>>> (tomcat5[05], jetty[56], geronimo-[tomcat/jetty], jboss-tomcat),  I had
>>>> to move deps back to Geronimo container-level. These include Axion,
>>>> which I know will upset Jeff. As I have stated before, WADI's  
>>>> dependence
>>>> on Axion is easily removed. If Jeff or anyone wants to look at  
>>>> replacing
>>>> it with Derby, it is fine with me, as long as they do some  testing and
>>>> confirm that having created a session on a single node and  
>>>> restarted it,
>>>> the session survives (if the DB is still running). This needs to be
>>>> tested on all supported containers. Axion was used because it is an
>>>> in-VM DB (so imposes no further integration dependencies on the  
>>>> Getting
>>>> Started stuff and is useful for unit-testing) and was in use by  
>>>> Geronimo
>>>> at the time. So I suggest that any replacement needs to also be  
>>>> able to
>>>> run in-vm aswell. As we go further and move WADI's actual  
>>>> configuration
>>>> from the app to the container-level, these issues will disappear and
>>>> WADI will be able to be hooked to whatever persistance mechanism is
>>>> shipped in Geronimo by default.
>>>> - Jan & Jeff , you may want to consider pushing some of this session
>>>> manager selection code up into a shared GeronimoWebContainer  
>>>> abstraction
>>>> so that you don't both end up maintaining similar but diverging  
>>>> code...
>>>> - I may have overlooked a couple of issues. If I come across them, I
>>>> shall post them.
>>>> Further work on Geronimo integration :
>>>> - more testing
>>>> - make a new WADI release and update geronimo-trunk to use it
>>>> - look at applying diffs to a G1.0 tree and producing a binary  
>>>> patch for
>>>> 1.0 distros.
>>>> - update website and release it
>>>> Jules
>>>> Jules Gosnell wrote:
>>>>> Guys,
>>>>> Jan and I have just refactored the Geronimo Jetty and Tomcat
>>>>> integrations to take the same approach to the installation of a 3rd
>>>>> party session manager, to ease the integration of WADI. This is now
>>>>> checked in on Geronimo's trunk.
>>>>> Each top level web container GBean now supports a pair of  
>>>>> attributes -
>>>>> LocalSessionManager and DistributableSessionManager. These may  be 
>>>>> used
>>>>> to override the container's choice of SessionManager for webapps  with
>>>>> and without the <distributable/> tag present in the WEB-INF/ web.xml,
>>>>> respectively.
>>>>> The attributes expect to be given a classname, if required, this  
>>>>> class
>>>>> will be loaded and instantiated. The resulting instance will be  used
>>>>> as the session manager. If not provided, the container will use a
>>>>> sensible default. Currently Jetty and TC are set up to use their  own
>>>>> default session managers in the local case and the correct WADI
>>>>> session manager in the distributable case.
>>>>> This means that the same WADI-enabled webapp, with its plan held
>>>>> internally (WEB-INF/geronimo-web.xml) may now be hot-deployed on
>>>>> either a Jetty or a Tomcat based Geronimo, without changes :-)
>>>>> I will post specific WADI issues to the WADI dev lists
>>>>> (, 
>>>>> dev-VfzB7HFVXnJICAUklc1DCNi2O/
>>>>> This shouldn't be seen as a final position on the subject -  there is
>>>>> still much to talk about, but is a useful interim step, that  
>>>>> allows us
>>>>> to have something working whilst we figure out how to go forward.
>>>>> Enjoy,
>>>>> 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)
>> *
>> *
>> *
>> * Open Source Training & Support.
>> **********************************/

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