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From Amila Suriarachchi <amilasuriarach...@gmail.com>
Subject Re: Supporting hierarchical service deployment
Date Fri, 04 Sep 2009 04:52:42 GMT
On Fri, Sep 4, 2009 at 10:05 AM, Chinmoy Chakraborty <cchinu@gmail.com>wrote:

> Paul,
>
> May be I dropped in from nowhere but I like to understand the idea. What is
> the purpose of maintaining duplicate data by allowing exact same AAR to be
> deployed in two different parts of hierarchy?
>
It is not exact AAR file. It is basically organise your AAR file in a
directory structure without putting all of the in the root directory.

eg.
repository/services/admin/AdminService.aar
repository/services/management/Management.aar
repository/services/tech/v1.1/Tech.aar
repository/services/tech/v1.0/Tech.aar

if you take latter two cases, it may be two versions of same .aar file which
user wants to active at the same time.


> I guess Axis2 should also support same service name with different
> namespaces. I have this kind of requirement in our project but right now
> it's a limitation.
>
if you can describe your requirement then we can see how it can be
supported.

As I understood what you want to have is same service name with different
name spaces to distinguish the version.
(I assume version depends on the namespace in your case)

Now the problem is what is the epr for these two services. In the above
solution epr is mapped to the folder structure. So people can invoke two
services with different eprs.

In your solution how to determine the service to invoke once a request
receive?

thanks,
Amila.

>
> Chinmoy
>
> On Thu, Sep 3, 2009 at 4:46 PM, Paul Fremantle <pzfreo@gmail.com> wrote:
>
>> Chinmoy
>>
>> I think that is cool, but I guess the aim of Isuru's initial proposal
>> was to allow the exact same AAR to be deployed independently in two
>> parts of the hierarchy. To me that is a good objective.
>>
>> Paul
>>
>> On Thu, Sep 3, 2009 at 11:59 AM, Chinmoy Chakraborty<cchinu@gmail.com>
>> wrote:
>> > Guys,
>> >
>> > How about introducing a new parameter (e.g ServiceClassNameSpace) in the
>> > services.xml to support directory hierarchy in the service?
>> >
>> > Chinmoy
>> >
>> > On Thu, Sep 3, 2009 at 3:47 PM, Isuru Suriarachchi <isurues@gmail.com>
>> > wrote:
>> >>
>> >> Hi all,
>> >>
>> >> As using '/' character may cause problems in dispatching, I just used a
>> >> separate character ('!') to represent the directory hierarchy in the
>> >> service. This allows all types of services to be deployed
>> hierarchically
>> >> without any problems (Including RESTful services).
>> >>
>> >> Ex: if we deploy the Echo service at
>> >> /repository/services/foo/bar/1.0.0/echo.aar, service name will be
>> >> foo!bar!1.0.0!Echo and the EPR will be like
>> >> ../axis2/services/foo!bar!1.0.0!Echo/echoString
>> >>
>> >> I've attached a new patch to the JIRA
>> >> (https://issues.apache.org/jira/browse/AXIS2-4479). This patch doesn't
>> >> contain any changes in dispatching logics. And also I've implemented
>> the
>> >> ability to deploy JAXWS, Pojo etc.. (which are coming from the
>> axis2.xml)
>> >> services hierarchically to make this effort complete. In addition to
>> that,
>> >> I've written some deployment tests for hierarchical services.
>> >>
>> >> Thanks,
>> >> ~Isuru
>> >>
>> >> On Sun, Aug 30, 2009 at 2:48 AM, keith chapman <
>> keithgchapman@gmail.com>
>> >> wrote:
>> >>>
>> >>> I've been out of touch with the Axis2 list for some time. Took a while
>> to
>> >>> read this thread. Just a few thouths on it.
>> >>>
>> >>> I don't think that this patch would effect the RESTfull behaviour in
>> any
>> >>> way. Its just that the user needs to be extra carefull if he wants to
>> use
>> >>> RESTfull services in cunjunction with the hierarchical services
>> concept. i.e
>> >>> if he has a services called foo do not use foo as a top level folder
>> in your
>> >>> hierarchy. Its simple as that. I guess been careful is the price you
>> have to
>> >>> pay if you wanna use hierarchical services.
>> >>>
>> >>> I like the idea of having hierarchical services in Axis2. Well I did
>> it
>> >>> once using the extension points of Axis2 but I'm +1 for having this
>> concept
>> >>> baked into Axis2.
>> >>>
>> >>> Also it would be good to base arguments on facts rather than religious
>> >>> beleifs. Quite a few design desicions made back then when Axis2 was
>> designed
>> >>> did not take stuff such as this into consideration. Well i'm not
>> blaming the
>> >>> initial Axis2 community for that. As the project evolves new features
>> such
>> >>> as this can be added. Good examples are features such as plugable
>> message
>> >>> builders/formatters (post 1.1), custom deployers (post 1.2 IIRC), the
>> >>> binding hierarchy concept (post 1.3) are features that were added
>> later in
>> >>> the cycle. I see the hierarchical service deployment feature as just
>> another
>> >>> addition to the wide variety of features of Axis2.
>> >>>
>> >>> Thanks,
>> >>> Keith.
>> >>>
>> >>> On Sat, Aug 29, 2009 at 1:24 PM, Sanjiva Weerawarana
>> >>> <sanjiva@opensource.lk> wrote:
>> >>>>
>> >>>> I forgot to address the issue with not being able to support RESTful
>> >>>> services. I think we can- we just need to change the REST dispatcher
>> (argh
>> >>>> if that's what its called its a terrible name!) to look at the
>> context path
>> >>>> of the service(s) and try filtering those out first.
>> >>>>
>> >>>> Sanjiva.
>> >>>>
>> >>>> On Sat, Aug 29, 2009 at 8:51 PM, Sanjiva Weerawarana
>> >>>> <sanjiva@opensource.lk> wrote:
>> >>>>>
>> >>>>> Deepal, I've read this entire thread and I'm confused as to
why
>> you're
>> >>>>> objecting.
>> >>>>>
>> >>>>> First of all, I think Isuru sent this thread into a bad start
by
>> using
>> >>>>> versioning as the reason for wanting to introduce hierarchical
>> service
>> >>>>> deployment. That was a mistake but as Andreas' comment pointed
out,
>> this is
>> >>>>> nothing more than the contextPath concept found in Java containers.
>> >>>>> Versioning is at most a special case but let's just take that
out of
>> the
>> >>>>> discussion because this is not about versioning. If you disagree
>> please
>> >>>>> explain why.
>> >>>>>
>> >>>>> Secondly, this can be done outside of Axis2 totally. All we
need to
>> do
>> >>>>> is write a new deployer and a dispatcher. There's no need to
waste
>> time with
>> >>>>> this type of pretty un-objective / emotional debate. However,
it was
>> >>>>> proposed as a mod to axis2 because it significantly improves
axis2
>> usability
>> >>>>> WITHOUT breaking any existing behavior. Or so was the belief.
So
>> let's go
>> >>>>> thru the discussion and if the view is that this is not necessary
in
>> axis2's
>> >>>>> default deployers etc. then no problem.
>> >>>>>
>> >>>>> Now I will explain why this approach is better than alternatives.
>> The
>> >>>>> basic requirement is that having a single flat naming scheme
for
>> services is
>> >>>>> unnecessarily limiting. Why? Because it requires everyone to
agree
>> on the
>> >>>>> service name as those names are global. If you're using Axis2
as a
>> library
>> >>>>> on a single developer machine that's not an issue. However,
if you
>> want to
>> >>>>> deploy an axis2 engine to host some number of services for a
larger
>> >>>>> organization then that invariably results in name conflicts.
I
>> assume you
>> >>>>> agree that's global names are a limitation.
>> >>>>>
>> >>>>> How do you fix it? One option is to use some naming convention
like
>> >>>>> what Java packages did for Java classes. So you can have
>> >>>>> /services/us.finance.address and /uk.services/marketing.address
if
>> (say) US
>> >>>>> finance and UK marketing orgs both want to have a service called
>> "address".
>> >>>>> That basically makes the fact that what you have are hierarchically
>> named
>> >>>>> services opaque to the Web infrastructure. For example, if you
were
>> >>>>> analyzing http logs to see the traffic you can't get a simple
answer
>> to "how
>> >>>>> many times have UK guys' services been used?". That's *exactly*
the
>> kind of
>> >>>>> wrong-headed thinking that got WS-* in trouble with the REST
guys
>> for
>> >>>>> improper use of REST (and I'm absolutely one of the early culprits
>> who made
>> >>>>> the mistake).
>> >>>>>
>> >>>>> Another approach is to have a way to specify the context path
in the
>> >>>>> service itself. If you remember, we used to have the concept
of
>> service name
>> >>>>> you could specify in service.xml itself (maybe its still there;
I
>> have no
>> >>>>> idea) - the idea was it would override the .aar file name if
thats'
>> there.
>> >>>>> This is similar- you can have in foo.aar a setting saying
>> >>>>> contextPath="finance/foo" and that means that's where the service
is
>> >>>>> deployed.
>> >>>>>
>> >>>>> The advantage of simply using the file system hierarchy to compute
>> that
>> >>>>> is just simplicity. The context hierarchy is visible to everyone
by
>> simply
>> >>>>> looking at the directory structure. If you check in the repository
>> into SVN
>> >>>>> (which I know a bunch of people do) it gives a simple way to
manage
>> >>>>> authorization for deployment for different people.
>> >>>>>
>> >>>>> I actually think we should support a contextPath=xxx option
in
>> >>>>> services.xml as well. However, treating the file system hierarchy
as
>> a
>> >>>>> hierarchy is, you know, rather natural.
>> >>>>>
>> >>>>> I think Isuru has shown that there is no extra performance loss
or
>> any
>> >>>>> other loss by supporting hierachically deployed services. You
DON'T
>> need to
>> >>>>> use them unless you want to of course - and if there's no hierarchy
>> there's
>> >>>>> no change at all (subject to having enough unit tests to make
sure
>> that old
>> >>>>> and new behavior for the old feature is not changed).
>> >>>>>
>> >>>>> Sanjiva.
>> >>>>>
>> >>>>> On Sat, Aug 29, 2009 at 7:05 PM, Deepal jayasinghe <
>> deepalk@gmail.com>
>> >>>>> wrote:
>> >>>>>>
>> >>>>>> >
>> >>>>>> >
>> >>>>>> > On Fri, Aug 28, 2009 at 8:30 PM, Andreas Veithen
>> >>>>>> > <andreas.veithen@gmail.com <mailto:andreas.veithen@gmail.com>>
>> >>>>>> > wrote:
>> >>>>>> >
>> >>>>>> >     Guys,
>> >>>>>> >
>> >>>>>> >     Are we actually discussing the right question?
Looking at the
>> >>>>>> > patch
>> >>>>>> >     proposed by Isuru, I have the impression that versioning
is
>> >>>>>> > merely one
>> >>>>>> >     use case, but that (in contrast to modules) the
code doesn't
>> >>>>>> > make any
>> >>>>>> >     assumption about the meaning of the hierarchy in
the
>> repository
>> >>>>>> > (it
>> >>>>>> >     could be version number, but it could also something
>> completely
>> >>>>>> >     different). Fundamentally the change is not about
versioning,
>> >>>>>> > but
>> >>>>>> >     about giving the user the possibility to define
the structure
>> of
>> >>>>>> > the
>> >>>>>> >     endpoint URL.
>> >>>>>> >
>> >>>>>> >
>> >>>>>> > yes. this should be the idea. it is to support hierarchical
>> service
>> >>>>>> > folder structure to mange
>> >>>>>> > services. Versioning is only one possible use case.
>> >>>>>> > I think this is a common requirement. For an example
if we take a
>> >>>>>> > web
>> >>>>>> > site people don't put
>> >>>>>> > all their .jsp or .html files in the root directory.
They manage
>> >>>>>> > them
>> >>>>>> > in a some meaningful
>> >>>>>> > folder structure and even page url maps to it.
>> >>>>>> You are mistaken in the case of web site .jsp files are
like .class
>> >>>>>> files. So even in Web Service we have package hierarchy.
>> >>>>>> > I can hardly think of any reason for opposing to introduce
such
>> >>>>>> > feature to axis2 service deployment provided
>> >>>>>> > that it *does not break existing functionality*.
>> >>>>>> If you look at the directory structure (as I told you before)
>> >>>>>> information repeat it self. It is analogous to "Shop is
closed
>> because
>> >>>>>> it is not open".
>> >>>>>> Just because feature X is good in project Y, we should not
>> introduce
>> >>>>>> that to Axis2.
>> >>>>>> If you or someone want to do such a feature of course they
can do
>> >>>>>> that,
>> >>>>>> just ad a new deployer  to handle the they want, even in
you case
>> we
>> >>>>>> can
>> >>>>>> do the same. Let's create a new deployer and manage anyway
you
>> like,
>> >>>>>> and
>> >>>>>> then if you think it is ok, then commit the new deployer
to Axis2.
>> >>>>>>
>> >>>>>> However I am not ok with introducing new URL pattern, I
think Isuru
>> >>>>>> already agreed to replace "/" with "-"
>> >>>>>> >
>> >>>>>> > Deepal,
>> >>>>>> > I feel you have given over weight to the versioning
support which
>> is
>> >>>>>> > a
>> >>>>>> > use case of this. In the way to have told
>> >>>>>> > people can have versioning without any support of axis2,
by just
>> >>>>>> > naming service in the way they need.
>> >>>>>> Yes. At the end of the day whether it is "/" or "-" would
become a
>> >>>>>> unique name. So it is the service name.
>> >>>>>> >
>> >>>>>> > Comming into the other point of probable break of existing
>> >>>>>> > functionality Can you please come up with the
>> >>>>>> > set of use case scenarios for this? Then we can ask
Isuru to
>> provide
>> >>>>>> > integration test for all these scenarios. This may
test the
>> existing
>> >>>>>> > functionality as well :)
>> >>>>>> I am sorry I do not have time to comeup with scenarios when
someone
>> >>>>>> add
>> >>>>>> new features, specially even without going through the existing
>> JIRA.
>> >>>>>> >
>> >>>>>> > I think we should not be pessimistic and think deployment
engine
>> is
>> >>>>>> > done for ever and any change will break it.
>> >>>>>> Not at all, how many changes we made, in this case my concern
is
>> not
>> >>>>>> the
>> >>>>>> deployment engine it is the URL pattern.
>> >>>>>> >
>> >>>>>> > Isuru,
>> >>>>>> > Please provide a set of integration tests for the scenarios
>> >>>>>> > mentioned.
>> >>>>>> :)
>> >>>>>>
>> >>>>>> Thanks,
>> >>>>>> Deepal
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> --
>> >>>>> Sanjiva Weerawarana, Ph.D.
>> >>>>> Founder, Director & Chief Scientist; Lanka Software Foundation;
>> >>>>> http://www.opensource.lk/
>> >>>>> Founder, Chairman & CEO; WSO2, Inc.; http://www.wso2.com/
>> >>>>> Member; Apache Software Foundation; http://www.apache.org/
>> >>>>> Visiting Lecturer; University of Moratuwa;
>> http://www.cse.mrt.ac.lk/
>> >>>>>
>> >>>>> Blog: http://sanjiva.weerawarana.org/
>> >>>>
>> >>>>
>> >>>>
>> >>>> --
>> >>>> Sanjiva Weerawarana, Ph.D.
>> >>>> Founder, Director & Chief Scientist; Lanka Software Foundation;
>> >>>> http://www.opensource.lk/
>> >>>> Founder, Chairman & CEO; WSO2, Inc.; http://www.wso2.com/
>> >>>> Member; Apache Software Foundation; http://www.apache.org/
>> >>>> Visiting Lecturer; University of Moratuwa; http://www.cse.mrt.ac.lk/
>> >>>>
>> >>>> Blog: http://sanjiva.weerawarana.org/
>> >>>
>> >>>
>> >>>
>> >>> --
>> >>> Keith Chapman
>> >>>
>> >>> blog: http://www.keith-chapman.org
>> >>
>> >>
>> >>
>> >> --
>> >> Senior Software Engineer,
>> >> WSO2 Inc. http://wso2.org/
>> >> Blog : http://isurues.wordpress.com/
>> >
>> >
>>
>>
>>
>> --
>> Paul Fremantle
>> Co-Founder and CTO, WSO2
>> Apache Synapse PMC Chair
>> OASIS WS-RX TC Co-chair
>>
>> blog: http://pzf.fremantle.org
>> paul@wso2.com
>>
>> "Oxygenating the Web Service Platform", www.wso2.com
>>
>
>


-- 
Amila Suriarachchi
WSO2 Inc.
blog: http://amilachinthaka.blogspot.com/

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