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From Jules Gosnell <>
Subject Re: -1 on checkin of 368344 was Re: [wadi-dev] Clustering: WADI/Geronimo integrations.
Date Thu, 12 Jan 2006 17:14:05 GMT
Jeff Genender wrote:

>Hi Jules.
>A few comments.  First, you made changes without discussing them on the
>dev lists.
There has been lots of discussion over the past week or two on both 
geronimo-dev and wadi-dev - I took this, along with my own findings when 
I looked at the code, and further offline discussion with Jan and Greg 
as we were making the changes, into account.

As I have clearly stated, if you don't like the way it has been done, it 
is only an iteration towards a final solution and you are welcome to 
contribute codewise. It is a major step forwards as it unifies the way 
that this is done between both containers, and further allows the use of 
clustering solutions other than WADI.

>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
I was involved in the recent threads (I started them and stoked them) 
and did discuss these issues. Please check the archive. To say that I 
was not open to discussion is not a tenable position.

> that have such a drastic
>impact on the Geronimo code base. 
Drastic ? It extends Geronimo to be able to run the WADI demo webapp, 
with no impact whatsoever on any non-distributable webapp.

> 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.
It is no longer an app dep - it is a container dep. The decision to use 
WADI is now made by the container, and as stated in my mail to the list, 
the config which determines this will soon move from the app to the 

I have also invited you to work on removing this dep from WADI.

>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.
Jeff, please take the time to read, run and understand the code before 
judging it.

As stated in my mail, a sensible default distributable session manager 
is hardcoded. This is overridable in the tomcat or jetty plan. This is a 
pretty standard way of doing things and means that any session manager, 
not just WADI may now be selected. This is a great step forward over the 
previous version where an important method signature included the 
WADIGBean type, which restricted distributable webapps to WADI and not 
other possible alternatives.

>3) You placed in the code, and Aaron worked pretty hard to
>clean those up.
I shall downgrade the level - apologies to Aaron - as I stated, this 
code is only an iteration towards a finished product.

>4) Your integration of setting the manager (no matter what) is a direct
>clash with the
with the..... what ?

>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.
Of the three reasons that you have given 2 are completely mistaken and 
one is trivial - in my book, insufficient technical argument for the 
rejection of a significant enhancement.

>Again, I will CC the G lists to make this clear, that I would like this
>change backed out.
In conclusion my change should remain for the following technical reasons.

- it fixes something that was broken
- it unifies two separate approaches into a single, more manageable 
approach, without sacrifice.
- it moves us in an agreed direction (from per-app to per-container 
based configuration)
- it is simpler than what it replaces - it frees us from requirements 
for an extra GBean and divergent Jetty and Tomcat geronimo-web.xml schemas.
- it is more flexible than the code that it replaces - it allows 
selection of ANY session manager, NOT JUST WADI, as was previously the case.
- it is small.

On the non-technical side of things:

- preceding this change, possible solutions were discussed on relevant 
dev lists at length.
- 3 Geronimo/WADI committers were involved in and agreed on the final 
minutiae of the change.
- by fixing, simplifying and unifying the WADI/Geronimo integration, 
this changes brings significant benefit to Geronimo.

If there are aspects of the change that you do not like, then we should 
simply work together, on top of the change, to resolve these issues.

By backing out the change, you break something that is fixed and remove 
all the beneficial code that you did not have issues with. If there are 
small issues, such as the level of a log message, then we should simply 
fix it and continue in a forward direction.



>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 Gosnell wrote:
>>>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,
>>>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
>>>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.

"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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