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From David Jencks <>
Subject Re: -1 on checkin of 368344 was Re: [wadi-dev] Clustering: WADI/Geronimo integrations.
Date Sat, 14 Jan 2006 19:58:57 GMT
I think this is a major step towards resolving this issue, thanks Jules.

I would like however to start a discussion about whether these  
changes should go into 1.0.1.  I will freely admit that I thought  
that clustering features were crammed into 1.0 at the last minute  
without adequate testing and discussion and that the results have  
been unsatisfactory and we would be better off without them in 1.0.   
I apologize for not objecting at the time.

Here are some factors that I think must be weighed in a decision  
about whether to include changes to clustering in 1.0.1 or 1.1:

- when will 1.1 come out.  The longer off it is, the more pressure to  
get something available sooner.
- the purpose of 1.0.1: essential bugfix or development free for all
- whether the immediate changes proposed for 1.0.1 will change any  
interfaces or deployment descriptors used in 1.0
- whether the proposed interfaces for 1.0.1 are expected to be stable  
or will change again for 1.1
- if the clustering changes go into 1.0.1, will they actually be  
production ready or at least as stable/usable as the rest of 1.0.1

Here is what I think about these factors:
- I want 1.1 to come out fairly soon, in about 3 months after 1.0.   
That should mean a feature freeze in perhaps 6 weeks.
- I want 1.0.1 to only fix severe problems in 1.0 and avoid changing  
any interfaces/ deployment descriptors
- AFAICT the proposals for clustering involve changing how it is set  
up in 1.0, both interfaces and plans.
- Based on the work so far I don't think we will have an acceptable  
stable solution for the interfaces and plans for 1.0.1
- I have no idea how stable clustering functionality might be.  AFAIK  
it has not been tested much if at all yet.

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?

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
>>>> (,
>>>> 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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