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Message-ID: <add18bc80809191007p1e55e0b8g114a2513f4656d9@mail.gmail.com>
Date: Fri, 19 Sep 2008 13:07:46 -0400
From: "Lin Sun" <linsun.unc@gmail.com>
To: dev@geronimo.apache.org
Subject: Re: svn commit: r694978 - in /geronimo/server/trunk:
 assemblies/geronimo-framework/ assemblies/geronimo-jetty6-javaee5/
 assemblies/geronimo-jetty6-minimal/ assemblies/geronimo-tomcat6-javaee5/
 assemblies/geronimo-tomcat6-minimal/ buildsupport/car-mav
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I think if we want to make users easier to build a project, the best
is that we can construct the dependency list automatically for the
user, perhaps at deployment time.   This would even save the user from
listing plugin groups as dependencies in various geronimo deployment
plans.  Maybe it is worthy while to investigate if it is possible to
do this?

Lin

On Wed, Sep 17, 2008 at 6:35 PM, Joe Bohn <joe.bohn@earthlink.net> wrote:
> David Jencks wrote:
>>
>> On Sep 15, 2008, at 11:41 AM, Joe Bohn wrote:
>>
>>> David Jencks wrote:
>>>>
>>>> On Sep 15, 2008, at 10:45 AM, Joe Bohn wrote:
>>>>>
>>>>> David Jencks wrote:
>>>>>>
>>>>>> On Sep 15, 2008, at 6:18 AM, Joe Bohn wrote:
>>>>>>>
>>>>>>> Thanks for making these changes David.  I think this mostly addresses
>>>>>>> my concern that plugingroups can be used anywhere plugins are used (it
>>>>>>> certainly helps now that they are all cars :-) ).
>>>>>>>
>>>>>>> So with the subject change ... is it now true what Lin mentioned
>>>>>>> earlier in the "[DISCUSS] plugingroups - another idea" thread:
>>>>>>>
>>>>>>> Lin Sun wrote:
>>>>>>> > For option 1, I guess I don't understand why we need the
>>>>>>> > classLoader
>>>>>>> > attribute.   I think for plugin groups, we should not add the
>>>>>>> > plugin
>>>>>>> > group itself to the classloader, but we should add the dependencies
>>>>>>> > to
>>>>>>> > the classloader.   For instance, if we support Joe's scenario, when
>>>>>>> > a
>>>>>>> > user specifies a plugin group as a dependency in his deployment
>>>>>>> > plan,
>>>>>>> > it would just add the dependencies that the plugin group depends on
>>>>>>> > to
>>>>>>> > the project's classloader.
>>>>>>>
>>>>>>> Will the dependencies of the plugingroup be added to the project's
>>>>>>> classloader?  That would certainly resolve any concerns.
>>>>>>
>>>>>> I _think_ they will be in the maven build's classloader but definitely
>>>>>> not in the geronimo classloader.   While this is inconsistent I don't yet
>>>>>> see a reasonable use case for a plugingroup that doesn't have a classloader
>>>>>> but does indicate a group of plugins that need to be added to some projects
>>>>>> classloader.  I needed the new functionality for other purposes so I haven't
>>>>>> spent a lot of time thinking about this but a real concrete use case would
>>>>>> go a long way for me.
>>>>>
>>>>>
>>>>> The scenario I had in mind is very simple.
>>>>>
>>>>> 1) A user has decided (for whatever reason) that they need a core
>>>>> server built on Geronimo including Jetty & Axis2.
>>>>> 2) The user will build multiple web applications and combine them on
>>>>> server images as the need arises and so they don't want to include the
>>>>> applications themselves in a custom server assembly.
>>>>> 2) To address the core server need, the user chooses to assemble their
>>>>> own server image with the two universal pre-reqs: the web-jetty and
>>>>> webservices-axis2 plugingroups.
>>>>> 3) The user then goes about building their web applications and
>>>>> generating geronimo plugins for these web apps to ease deployment.  They
>>>>> want to ensure these applications are installed in the correct server
>>>>> configuration so they set the prereqs for the applications to match the core
>>>>> server image that they had earlier constructed - a prereq on the web-jetty
>>>>> and webservices-axis2 plugingroups.
>>>>> 4) The user will then install the server in the appropriate location(s)
>>>>> and deploy combinations of the applications on the as necessary on the
>>>>> server instances.
>>>>>
>>>>> Of course it is more correct to have the applications prereq the
>>>>> individual plugins necessary for jetty and axis2 runtimes rather than the
>>>>> plugingroups.  However, that would mean that the user must understand the
>>>>> detailed plugins for building applications but only the plugingroups for
>>>>> building server images ... and the whole point of the plugingroups was to
>>>>> simplify things for the user so they could deal with higher level concepts.
>>>>>  If that simplification makes sense for assembling a server (a relatively
>>>>> infrequent activity) why would it not also make sense for assembling an
>>>>> application (a somewhat more frequent activity)?
>>>>>
>>>>> And yes, I understand (as will the user) that the plugingroups may be
>>>>> pulling in more than they really need to run the applications - esp. if we
>>>>> continue to combine core function, deployers, and console extensions in the
>>>>> plugingroups.  That may be a valid reason to alter the granularity of the
>>>>> groups we are creating.  If not, another reason to split things up a little
>>>>> finer is to facilitate the construction of servers without deployment
>>>>> capabilities - but that's really a separate discussion.
>>>>
>>>> To me it seems more like you are suggesting plugin groups as a
>>>> workaround to another problem in the current plugin system, and I don't
>>>> think your suggestion will really help.
>>>> If you are using maven to build plugins, currently you have to specify
>>>> explicitly in the car-maven-plugin which deployment plugins you want to use,
>>>> and include them as (provided) dependencies in the pom. This means you need
>>>> to know what you want quite explicitly, and I don't see how plugin groups
>>>> can help with this yet.... certainly an area for discussion.
>>>> Now, the deployers all add the required dependencies to the plan, such
>>>> as in your example axis2 and jetty, so the app certainly won't start without
>>>> those present.  However at the moment we have no way for the c-m-p to find
>>>> out about those added dependencies and add them to the geronimo-plugin.xml
>>>> so you have to list them yourself.
>>>> It seems to me that if we can somehow use plugin groups in the c-m-p
>>>> configuration to specify more concisely what deployers we want, and get the
>>>> dependencies added by the deployers into the geronimo-plugin.xml, then we
>>>> will have the convenience you want without the extra classloader or funny
>>>> "this isn't really a plugin, include my dependencies" behavior that I'm
>>>> nervous about.
>>>
>>> Yes, you are correct that the deployers are an issue when configuring the
>>> c-m-p.  That is a important issue, but not the one I was trying to discuss
>>> here.
>>
>> I think they are related.... see below :-)
>
> No doubt they are related.  I was only trying to tackle one thing at a time.
>  If plugingroups were interchangeable with plugins we could leverage
> deployer plugingroups in c-m-p configuration as well.
>
>>>
>>>
>>> If you look at the jaxws-calculator sample it demonstrates something
>>> similar to my contrived scenario.   The jaxws-calculator-jetty plugin has
>>> dependencies on 3 other plugins - jetty6, jasper, and cxf (to match my
>>> scenario above let's just pretend this is axis2 rather than cxf).  If the
>>> user is already familiar with a set of plugin groups they would probably
>>> find it more intuitive to declare dependencies on the groups rather than
>>> individual plugins.  In this example they could declare dependencies on
>>> web-jetty and webservices-axis2 to match what they had specified when
>>> assembling the server.
>>>
>>
>> What I'd like to see is that the user configures the c-m-p so it works and
>> deploys against the jetty web container, jasper jsp stuff, and axis2 web
>> services.  I'd like everything else to flow from that without any more user
>> input.  What's missing right now is
>> - easier way to set the required deployers (although it isn't too hard
>> now)
>> - getting the default environment dependencies from the builders into the
>> geronimo-plugin.xml
>>
>> If you are deploying something into a running server I want the generated
>> geronimo-plugin.xml to include all these default env dependencies as well:
>> the result should be that the user only has to specify what server bits they
>> want once, either in the c-m-p "which deployers to use" configuration or
>> what is running in the server they deploy against.
>>
>> To reiterate over and over again once more :-/ I think getting the default
>> env deps into the geronimo-plugin.xml removes any usefulness for the plugin
>> groups as explicit dependencies for user applications.  I think we might
>> look for a way to simplify or automate choosing the deployers to use. I
>> don't know if something like plugin groups might be useful here, or not.  We
>> might look into byte code dependency analysis like dependency:analyze uses
>> to detect use of servlet, ejb, connector, jms, .... classes and pick them
>> from some kind of list, but I'm not sure this relates well to the plugin
>> groups you are thinking of.  I'm thinking of a list that says
>> "jetty-deployer, cxf-deployer, openejb-deployer, jasper-deployer..."
>
> Ok, I see what you are saying.  Rather than call out the dependencies
> directly and in addition to that call out the deployers in the c-m-p
> configuration - the user could skip the dependencies and rely on the
> deployer's default environment to fill them in.
>
> Perhaps that will work most of the time for plugingroups that we create that
> also have some related deployer (and maybe all of our plugingroups will have
> deployer equivalents).   But will all dependencies included in a plugingroup
> also be pulled in by some deployer's default environment?
>
> However, what happens with user or 3rd party created plugingroups?  Will
> they always have comparable deployers and hence default environments so they
> don't need to be specified as a dependency?
>
> Perhaps the user wants the base server to include some core Geronimo bits
> (Jetty, Axis2, etc...) and some of their own functions ... perhaps a
> plugingroup of utilities provided by some 3rd party.  For example, let's say
> there is a plugingroup that includes several common debug utilities like
> configurable logging, first-failure data capture, policy validation, etc...
> let's call it "debug utilities".  Next the user assembles a server using a
> combination of the geronimo plugingroups and "debug utilities" for a base
> server image.  They plan on using this image multiple times to manage
> multiple configurations rather than creating unique assemblies.  If they
> want to build plugins for their applications that will be deployed to this
> image, they can configure the c-m-p deployers and thereby pull in the
> default environment dependencies for the geronimo plugingroups.  But they
> still have to include the individual plugins from "debug utilities" as
> dependencies if we don't support using the plugingroup in as dependencies.
>
> Again, my goal is only to get some consistency for the end user.  I still
> think it's a good idea that our users will appreciate.
>
> Some more rambling thoughts ....
> While I understand and appreciate the idea of configuring the deployers for
> c-m-p and having them pull in the necessary default environments, it seems a
> bit backward from a user perspective.  If we want users to embrace plugins
> and using maven to construct them, I think it would make more sense to a
> user if we approach the problem from the other angle.  A user creating a
> plugin probably already has some idea of the dependencies they will need
> (either plugins or plugingroups if appropriate).   If we let them specify
> the dependencies we should be able to determine which of those dependencies
> requires a particular deployer (at least dependencies of ours).  We could
> make it more general  purpose by always naming the deployers consistently
> based upon the module that they support (ex. -deployer in the artifactId).
> I'm not sure how we would accomplish that (perhaps another maven plugin that
> front-ends c-m-p) or how we would know if a deployer exists for a given
> plugin.  But it seems a bit more intuitive to me than telling the user
> figure out the c-m-p deployers based upon their dependencies and then omit
> the dependencies so that the deployers can pull them in via the default
> environment.
>
> I hope I'm not driving you crazy ... it just seems obvious to me that users
> will want to leverage plugingroups the same way that they leverage plugins.
>
> Joe
>
>
>>
>> thanks
>> david jencks
>>
>>
>>
>>
>>>
>>>> thanks
>>>> david jencks
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Joe
>>>>>
>>>>>
>>>>>> thanks
>>>>>> david jencks
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Joe
>>>>>
>>>
>>
>>
>
>