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From David Jencks <david_jen...@yahoo.com>
Subject Re: Implementing rfc66 in Geronimo
Date Mon, 18 Jan 2010 08:43:40 GMT

On Jan 18, 2010, at 12:33 AM, Rex Wang wrote:

>
>
> 2010/1/18 Jarek Gawor <jgawor@gmail.com>
> On Thu, Jan 14, 2010 at 9:47 PM, Ivan <xhhsld@gmail.com> wrote:
> > I am thinking that while implementing the WAB extender, how does  
> it use
> > current deployer ? There might be something need to consider :
> > 1. Current Geronimo deployer is designed for two steps deployment,  
> which
> > means that it needs to install package to the OSGI environment  
> twice, how to
> > handler it in the extender ?
>
> Right now I think the idea is to modify our deployment process to 1)
> work directly with a Bundle object and 2) not to create any additional
> or temporary bundles during deployment and just create a configuration
> object that the extender can load/start/stop.
>
> That makes me to think about if we can make our Geronimo plugins  
> more extender-like. Such as Ivan said, currently we need deploy a  
> car twice in order to firstly install all the depending bundles and  
> generate the config.ser, then using the config to instantiate  
> gbeans. This is very different to the RFC66 WABs.
> Before starting the WAB, extender even does not know the existence  
> of it. A WAB is considered as a normal bundle with other bundles. So  
> our extender need track the WAB starting and generate config.ser and  
> instantiate gbeans all in one step. Hence, what is the standard way  
> to install a war? I see two approaches as follows:
> 1. The current way of making the war a geronimo-lize war before  
> start it.
> 2. Convert the war to WAB and deploy the WAB, after start it,  
> extender will find it and generate geronimo information. That is  
> what RFC66 spec required.
> I think we should choose the #2.

I am not yet convinced that rfc 66 and #2 are good ways to deploy web  
apps.  We want to support them but that doesn't mean they are ideal.   
The main problem I have with rec66 like methods is that you end up  
with extra data needed to start the geronimo plugin-ized WAB that  
isn't in the WAB.  So, you can't just copy the plugin into another  
server, you have to go through deployment via the rfc66 extender on  
every server.  This pretty much negates most of the good points about  
geronimo plugins.  We might decide this is the direction we want to go  
in, but we should talk about it in detail.

thanks
david jencks


>
> -Rex
>
>
> > 2. Where and when we store the configuration datas ? Not sure in  
> the spec,
> > there is any description about the contain's behavior, or it would  
> analysis
> > the WAB each time while starting it ?
>
> We could store that information in the bundle private storage area. If
> the information is already there and the bundle hasn't been updated we
> could reuse the information and skip the deployment.
>
> > 3 . About the double start, while restarting Geronimo, it should  
> be possible
> > to use location or artifact, but since WAB could be installed by  
> any other
> > applications, so location/artifact might not enough.
>
> I'm not worried about this now but potentially yes. Maybe this won't
> even be an issue.
>
> Jarek
>
> >
> > 2010/1/14 Rick McGuire <rickmcg@gmail.com>
> >>
> >> Rex Wang wrote:
> >>>
> >>>
> >>> 2010/1/14 Jarek Gawor <jgawor@gmail.com <mailto:jgawor@gmail.com>>
> >>>
> >>>    Hey all,
> >>>
> >>>    I've been looking into implementing rfc66 support in Geronimo  
> a little
> >>>    bit more. Here are some things that we need to do and my
> >>>    thoughts/impressions about them:
> >>>
> >>>    1. WAR to WAB converter. Installs webbundle: url handler that  
> converts
> >>>    standard WAR files into Web Application Bundles (WAB). The  
> converter
> >>>    code was contributed by IBM to Apache Aries but so far it has  
> not been
> >>>    moved to trunk yet. This code will probably need some updates  
> but I
> >>>    think we could just mostly use it as it is in Geronimo.
> >>>
> >>>    2. WAB extender. Watches for WABs to be started in the  
> framework and
> >>>    performs the necessary steps to deploy the applications.
> >>>     a. In Geronimo we will need a custom extender that effectively
> >>>    invokes Tomcat/JettyWebModuleBuilders to deploy the  
> application. There
> >>>    might be an extender implementation donated to Aries at some  
> point but
> >>>    I don't think we will be able to use since it most likely  
> will use the
> >>>    Tomcat or Jetty API directly to deploy the application. In  
> Geronimo we
> >>>    build the GBeans which then use Tomcat/Jetty API to set  
> everything up.
> >>>     b. The biggest issue that I see with Geronimo WAB extender is
> >>>    updating the WebModuleBuilders (or actually the whole  
> deployment
> >>>    process) to work with Bundle objects. Right now the  
> deployment process
> >>>    for the most part assumes it is working with JarFiles.
> >>>
> >>> So, what is the standard method to install/deploy a WAB into  
> Geronimo
> >>> 3.0? From the osgi perspective, that should be the same with  
> installing a
> >>> normal bundle to framework, and then the extender will track  
> this and help
> >>> deploy it to geronimo by instantiating some gbeans. Should we  
> support the
> >>> geronimo deployment process such as deploy a WAB with a external  
> plan?
> >>
> >> One key point with WABs is to remember that a WAB is an OSGi  
> programming
> >> construct and even though it is running under Geronimo, it should  
> function
> >> under OSGi rules.  One key point here is any application may  
> install and
> >> start a WAB bundle using a BundleContext without ever knowing  
> anything about
> >> the hosting Geronimo server.  That's the key purpose of the  
> extender...it
> >> processes any bundle that has the manifest entries that identify  
> this as a
> >> WAB and take the steps necessary to deploy this.  The bundle in  
> question
> >> might not have gone through the Geronimo deployment process first.
> >>>
> >>>     c. Rick has some initial extender code in the sandbox that  
> we should
> >>>    be able to reuse (or at least parts of it) in Geronimo.
> >>>     d. Things to keep in mind:
> >>>       1. The specification talks about support for lazy bundles.  
> More
> >>>    specifically, that a request on static resource of a lazy  
> activated
> >>>    bundle should not cause the bundle to become fully  
> activated.  This
> >>>    might be tricky to implement in Geronimo and would require  
> changes to
> >>>    existing code. However, support for lazy bundles seems to be  
> optional
> >>>    in the specification.
> >>>       2. The specification says that “it should be possible for  
> a Web
> >>>    application bundle to remain installed when its Web Container  
> is
> >>>    dynamically replaced”. Which I think it means what happens if  
> somebody
> >>>    deploys WAB, then stops Tomcat container and starts Jetty  
> container
> >>>    all at runtime. Does the application continue to work? Should  
> Geronimo
> >>>    support this case? It is an optional feature.
> >>>
> >>> Does that indicate each WAB will contain several plans for  
> different
> >>> containers? That might require a way to distinguish the plans.
> >>>
> >>>       3. The extender might need to track somehow which WABs were
> >>>    already deployed to prevent double start problems. Once some  
> WAB is
> >>>    deployed and the Geronimo server is restarted, Geronimo will  
> attempt
> >>>    to start the generated configuration/plugin for the WAB.  
> Starting of
> >>>    the plugin will also start the actual WAB and then the  
> extender will
> >>>    see the starting bundle and attempt to deploy the WAB again.
> >>>
> >>> Yes, I think the other RFC66 implementation also need to take  
> care of it.
> >>>
> >>> Thanks
> >>> -Rex
> >>>
> >>>
> >>>    3. Annotation and resource discovery.
> >>>     a. The specification does not describe an exact way of  
> discovering
> >>>    annotations or resources in a WAB. For example, if WAB  
> imports some
> >>>    package from another bundle, are all classes in that package  
> scanned
> >>>    for annotations? What about resources in META-INF directory?  
> Are the
> >>>    bundles wired to the WAB checked for META-INF resources?   
> These are
> >>>    some unanswered questions that we need to keep track of.
> >>>     b. In certain cases (e.g. servlets 3.0, EJBs, etc.) we will  
> need to
> >>>    discover all accessible classes in bundle class space that  
> have a
> >>>    given annotation. For that we will need annotation discovery  
> code that
> >>>    might need to know how to scan bundles based on Bundle- 
> Classpath and
> >>>    possibly on Import-Packages, DynamicImport-Package, Require- 
> Bundle,
> >>>    etc. depending on what the specification will say. The  
> annotation
> >>>    scanning code might get even more difficult if it needs to  
> support
> >>>    lazy bundles.
> >>>     c. Tag library scanning might require similar code as used in
> >>>    annotation discovery since the tld files can be included in any
> >>>    directory in a JAR under the META-INF directory. This also  
> depends on
> >>>    what the final specification will say.
> >>>
> >>>    4. JSP Runtime Compilation. Not sure yet what that will require
> >>>    (if anything).
> >>>
> >>>    5. JNDI (RFC 142) integration. Get services from service  
> registry
> >>>    using JNDI lookup using osgi:service/<interface> name (and  
> therefore
> >>>    OSGi services could be injected via standard @Resource  
> annotation).
> >>>    Support for RFC 142 is recommended but not required by RFC  
> 66. This is
> >>>    an optional item but useful to have. There is RFC 142  
> implementation
> >>>    in Apache Aries that seems pretty complete so it just needs  
> to be
> >>>    integrated in Geronimo.
> >>>
> >>>    I think updating the WebModuleBuilders (2.b) will take the  
> most time
> >>>    and effort. The annotation and resource discovery (3.b and 3.c)
> >>>    shouldn't be a lot of work but it's still not very well  
> defined in the
> >>>    specification and that is something we need to keep track of.  
> The good
> >>>    news is that we can work on all (except maybe the JSP  
> compilation) of
> >>>    these items at the same time without stepping on each other's  
> feet.
> >>>    Also, if the specification decides to require support for  
> lazy bundles
> >>>    that will cause some fairly major changes in Geronimo. For  
> now, I
> >>>    think we should assume that lazy bundles are optional and  
> assume
> >>>    fairly simple rules for annotation and resource discovery  
> code (i.e.
> >>>    scan jars files or directories specified on the Bundle- 
> ClassPath
> >>>    only).
> >>>
> >>>    Comments?
> >>>
> >>>    Jarek
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> Lei Wang (Rex)
> >>> rwonly AT apache.org <http://apache.org>
> >>
> >
> >
> >
> > --
> > Ivan
> >
>
>
>
> -- 
> Lei Wang (Rex)
> rwonly AT apache.org


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