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From Sanjiva Weerawarana <sanj...@opensource.lk>
Subject Re: [axis2] Improvements to Service life cycle in handling - setOperationContext not thread-safe??!!
Date Tue, 10 Oct 2006 13:33:50 GMT
I think I agree with you. How about we drop setOperationContext() and
introduce Axis1-style MessageContext.getCurrentContext() which returns
it for this thread? Have to be careful to put it in TLS and take it off!

We must be careful to tell users that instance variables are not
supported; you have to use MessageContext properties to store state (or
wherever else).

Sanjiva.

On Sun, 2006-09-24 at 14:12 +0200, Christopher Sahnwaldt wrote:
> Entered as http://issues.apache.org/jira/browse/AXIS2-1224 .
> I set the priority to blocker as David suggested.
> 
> IMHO it's probably best to drop the method. Many users will use it in an
> intuitive but wrong way. The only way to store the data it provides is an
> instance variable, and telling users to either use only request scope or use
> a ThreadLocal to store the data does not seem to be compatible with the
> rule of least surprise. Something like MessageContext.getCurrentContext()
> in Axis 1 might be better.
> 
> Bye,
> Christopher.
> 
> Davanum Srinivas wrote:
> > Chris,
> >
> > Can you please raise a new issue in JIRA?
> >
> > thanks,
> > dims
> >
> > On 9/23/06, Christopher Sahnwaldt <chrisahn@gmx.net> wrote:
> >> Something worries me:
> >>
> >> > setOperationContext(OperationContext) - per call.  The messageContext
> >> > can be obtained to gain per call instance information.
> >>
> >> That doesn't seem to be thread-safe, does it? If I understand this
> >> correctly, one service object is created per application (if the
> >> service has application scope). When a request comes in, Axis calls
> >> the setOperationContext method, and the service object may store the
> >> OperationContext or the MessageContext. Then Axis calls the actual
> >> service method, in which the service code can access the stored
> >> OperationContext or MessageContext. But what if two requests come
> >> in almost simultaneously? The following sequence of method calls
> >> may occur:
> >>
> >> - Axis calls setOperationContext with context for request A, the
> >>   service object stores the context in an instance field.
> >> - Axis calls setOperationContext with context for request B, the same
> >>   service object stores the context in the same instance field and
> >>   thus *overwrites* the context for call A.
> >> - Axis calls the service method with the input parameters for request A.
> >> - The service method processes the call, using data from the stored
> >>   context, and thus *mixes the input parameters for call A with the
> >>   context data for call B*. Anything can happen...
> >> - Finally, Axis calls the service method with the input parameters
> >>   for call B, the service method processes the call, using data from
> >>   the stored context, and thus correctly uses the input parameters
> >>   for call B with the context data for call B. Probably ok, unless
> >>   the service method updated the context in some way during the call
> >>   for request A.
> >>
> >> But I hope I'm wrong or misunderstood or forgot something... ;-)
> >>
> >> Axis 1 avoided this problem by MessageContext.getCurrentContext(),
> >> which gives access to the MessageContext *for the current thread*
> >> from within any service method, without the need for a
> >> setMessageContext (or setOperationContext) method on the service
> >> object.
> >>
> >> Bye,
> >> Christopher.
> >>
> >>
> >> Tony Dean wrote:
> >>
> >> > Can we fully document the logical semantics behind each method?
> >> >
> >> > init(ServiceContext) - To me this use to mean application init.  
> >> Now it means session init.  However, when running 
> >> scope="Application", it is analogous to application init since you 
> >> will only have one session;  but, still probably not appropriate to 
> >> think in those terms.
> >> >
> >> > How should an application use this method?  A session use-case 
> >> would be nice.
> >> >
> >> > destroy(ServiceContext) - inverse of init()
> >> > Use-case?
> >> >
> >> > setOperationContext(OperationContext) - per call.  The 
> >> messageContext can be obtained to gain per call instance information.
> >> >
> >> > StartUp() - one time initialization... DB connections etc...
> >> > Shutdown() - inverse of StartUp()
> >> >
> >> > Any more insight or corrections to pattern usage would be grateful...
> >> >
> >> > Thanks.
> >> >
> >> > -----Original Message-----
> >> > From: robert lazarski [mailto:robertlazarski@gmail.com]
> >> > Sent: Friday, September 15, 2006 8:49 AM
> >> > To: axis-dev@ws.apache.org
> >> > Subject: Re: Improvements to Service life cycle in handling
> >> >
> >> > That makes sense to me. I've been using startUp() and it doesn't 
> >> really fit with the other methods of the interface in its current 
> >> form. +1 for 1.1 since its interface changes and it'd be better to do 
> >> it now.
> >> >
> >> > One question: Currently you need this in services.xml to get 
> >> startUp() to invoke:
> >> >
> >> > <parameter name="load-on-startup" locked="false">true</parameter>
> >> >
> >> > I plan on testing this when its ready ... since the spring tutorial 
> >> depends on it ... so I thought I'd ask if the services.xml param will 
> >> remain the same.
> >> >
> >> > Thanks,
> >> > Robert
> >> >
> >> > On 9/14/06, Deepal Jayasinghe <deepal@opensource.lk> wrote:
> >> >
> >> >> Hi All;
> >> >>
> >> >> Currently we have an interface called Service and which has few
> >> >> methods that are used to manage session (or else user can add those
> >> >> method into service impl class w.o implementing the interface). And
> >> >> that interface has the following methods ;
> >> >>
> >> >> - startUp
> >> >> - init
> >> >> - setOperationContext
> >> >> - destroy
> >> >>
> >> >> Three of them are for managing service life cycle ;
> >> >> - init - will be called when the session start
> >> >> - setOperationContext - immediately before calling actual java method
> >> >> - destroy - will be call when the session finishes
> >> >>
> >> >> Remember all those method work if and only if you use Axis2 default
> >> >> message receiver or you code gen.
> >> >>
> >> >> The method startUp is not session related method , which is useful
> >> >> when you want to initialize database connections , create thread etc
> >> >> ... at the time when you deploy the service. In the mean time
> >> >> interface name Service is bit confusing to me AFAIK it should be
> >> >> ServiceLifeCycle. And having method like startUp in that interface

> >> confuses the users.
> >> >>
> >> >> So how about the following changes ;
> >> >> - Rename Service interface into ServiceLifeCycle
> >> >> - Then remove startUp method from that interface.
> >> >>
> >> >> There should be a some other interface (like Module interface) and
> >> >> which should be optional as well , to have the method startUp. If
> >> >> someone want to open DB connection or anything at the time of service
> >> >> deploying , then he need to implement that interface (and for me 
> >> which
> >> >> is identical to Module interface). So with this change service 
> >> element
> >> >> inside the services.xml will be change to following
> >> >>
> >> >> <service name="foo" *class="implementation class of the interface
"*>
> >> >> <parameter name="ServiceClass">ServiceClass</parameter>
> >> >> </service>
> >> >>
> >> >> Here the class attribute is optional , so if someone want to have
> >> >> loadonStartup feature then he need to implement the Service interface
> >> >> (new one) and put the impl name as the class attribute. This is very
> >> >> useful if your service implementation class is not java (if you are
> >> >> writing a groovy serice).
> >> >>
> >> >> So new Service interface will be look like follows; public interface
> >> >> Service{ //will be called when service is deployed public void
> >> >> startUp(ConfigurationContext configctx, AxisService service); //will
> >> >> be called when Axis2 server showdown or when service removed from the
> >> >> system public void shutDown(ConfigurationContext configctx,
> >> >> AxisService service); }
> >> >>
> >> >> And ServiceLifeCycle interface will look like below;
> >> >>
> >> >> public interface ServiceLifeCycle {
> >> >> public void init(ServiceContext sc);
> >> >> public void setOperationContext(OperationContext operationContext);
> >> >> void destroy(ServiceContext sc); }
> >> >>
> >> >>
> >> >> I am +1 on doing this for Axis2 1.1 :)
> >> >>
> >> >> Suggestions ........
> >> >>
> >> >> Thanks
> >> >> Deepal
> >> >>
> >> >>
> >> >>
> >> >> ---------------------------------------------------------------------
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> >> >>
> >> >>
> >> >>
> >> >
> >> > ---------------------------------------------------------------------
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> >> >
> >> >
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> >> >
> >>
> >>
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> >>
> >>
> >
> >
> 
> 
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