Re: Declarative Exception Handling in ServiceMix
On 10/5/06, Ralf Wunsch <[EMAIL PROTECTED]> wrote: gnodet wrote: > > A few questions: > * How are the errorHandler and errorHandlerConfig related ? > * If I want to handle a given exception specifically, i guess > I need to implement a custom errorHandler, right ? > * how does the errorHandler plug into the jbi container ? > * If i have more than one ErrorHandlerComponent in the flow it should be possible to use one ErrorHandler with different configurations for each ErrorHandlerComponent (e.g. to specify different targets for different types of failed messages). To provide this the configuration for the ErrorHandler has been extracted and assembled in the ErrorHandlerConfig XBean. * In my opinion the error handler hook and the handlers strategy should be separated. I am involved in a migration project (from a commercial EAI solution to open source). In the current EAI system an error handler is always implemented. We want to migrate this solution that is based on a set of database stored rules. I think there can be a lot of error handler strategy implementations. One default handler can be an implementation as discussed before. * At this time i am using my own extension of the JBIContainer. This extension registeres an ErrorEventListener as EventListener by default. I have not found a way to configure event listeners in the deployment descriptor. The ErrorHandler is a attribute of the extended container (the getter/setter methods are using the ErrorEventListerners 'errorHandler' attribute). Have you tried something like: It works. Best regards, Ralf Wunsch -- View this message in context: http://www.nabble.com/Declarative-Exception-Handling-in-ServiceMix-tf2161788.html#a6661952 Sent from the ServiceMix - Dev mailing list archive at Nabble.com. -- Cheers, Guillaume Nodet
Re: Declarative Exception Handling in ServiceMix
gnodet wrote: > > A few questions: > * How are the errorHandler and errorHandlerConfig related ? > * If I want to handle a given exception specifically, i guess > I need to implement a custom errorHandler, right ? > * how does the errorHandler plug into the jbi container ? > * If i have more than one ErrorHandlerComponent in the flow it should be possible to use one ErrorHandler with different configurations for each ErrorHandlerComponent (e.g. to specify different targets for different types of failed messages). To provide this the configuration for the ErrorHandler has been extracted and assembled in the ErrorHandlerConfig XBean. * In my opinion the error handler hook and the handlers strategy should be separated. I am involved in a migration project (from a commercial EAI solution to open source). In the current EAI system an error handler is always implemented. We want to migrate this solution that is based on a set of database stored rules. I think there can be a lot of error handler strategy implementations. One default handler can be an implementation as discussed before. * At this time i am using my own extension of the JBIContainer. This extension registeres an ErrorEventListener as EventListener by default. I have not found a way to configure event listeners in the deployment descriptor. The ErrorHandler is a attribute of the extended container (the getter/setter methods are using the ErrorEventListerners 'errorHandler' attribute). Best regards, Ralf Wunsch -- View this message in context: http://www.nabble.com/Declarative-Exception-Handling-in-ServiceMix-tf2161788.html#a6661952 Sent from the ServiceMix - Dev mailing list archive at Nabble.com.
Re: Declarative Exception Handling in ServiceMix
Sounds good. Nice work ! A few questions: * How are the errorHandler and errorHandlerConfig related ? * If I want to handle a given exception specifically, i guess I need to implement a custom errorHandler, right ? * how does the errorHandler plug into the jbi container ? If you want to donate this code, feel free to raise a JIRA issue and attach the code. I think it would be a nice addition. On 10/5/06, Ralf Wunsch <[EMAIL PROTECTED]> wrote: Ralf Wunsch wrote: > > > We are starting a new EAI project. At this time ServiceMix is our choice > for the implementation plattform. We have strong requirements for > monitoring and control issues. At this one aspect is the handling of > unexpected errors. For this reason i have implemented the following error > handler solution. > > > > The error handling solution delegates errors or faults detected in > analysis of the MessageExchange objects to an ErrorHandler implemented as > XBean. This bean is used by an ErrorHandlerComponent (a JBI component > embedded in the flow) or by the JBIContainer (the centralized way) or > both. > > http://www.nabble.com/file/290/error-handler-embedding.png > > The ErrorHandler can cancel transactions and stop the container or the > source component (all cofigurable). Furthermore it's possible to route the > error or fault messages and the actuating message to a configurable > target. In this case ist possible to embed one or more > ErrorHandlerComponents into the flow. > > http://www.nabble.com/file/291/error-handler-flow.png > > Such an ambedded ErrorHandlerComponent borrowed by the EIP WireTap ensures > that the rerouted message from the source will be in a well know format > (the centralised approach can't accomplish this). The embedded and the > centralized approach can be used in combination. For synchronization the > ErrorHandlerComponent sets a Property on the outgoing MessageExchange and > the ErrorEventListener does nothing as long as this property can be found > in the MessageEchange which signals a fault or an error. > > > A sample configuration... > > > <bean id="errorHandler" > class="de.eval.eai.error.DefaultErrorHandler"> > </bean> > ... > <bean id="errorHandlerConfig" > class="de.eval.eai.error.ErrorHandlerConfig"> > <property name="shutdownOnFault" value="true" /> > <property name="rollbackOnFault" value="false" /> > </bean> > ... > <test:container id="jbi" >useMBeanServer="true" >createMBeanServer="false" >dumpStats="true" >statsInterval="10" >errorHandler="#errorHandler" >errorHandlerConfig="#errorHandlerConfig"> > ... > <sm:activationSpecs> > ... > <sm:activationSpec componentName="errorHandler"> > <sm:component> > <eai:component> > <eai:endpoints> > <eai:errorHandler service="errorHandler" > endpoint="endpoint"> > <eai:target> > <eai:exchange-target service="transformer" /> > </eai:target> > <eai:disqualifyTarget> > <eai:exchange-target service="failedQueue" /> > </eai:disqualifyTarget> > <eai:errorTarget> > <eai:exchange-target service="errorQueue" /> > </eai:errorTarget> > <eai:faultTarget> > <eai:exchange-target service="faultQueue" /> > </eai:faultTarget> > <property name="shutdownOnFault" value="true" /> > <property name="rollbackOnFault" value="false" /> > </eai:errorHandler> > </eai:endpoints> > </eai:component> > </sm:component> > </sm:activationSpec> > ... > > > Two questions: > > > Ist this a accurate ServieMix way (in accordance with the ideas of > ServiceMix)? > > > Is it on behalf of the project or the communitiy to reuse this solution? > > > Thanks, > Ralf Wunsch > > -- View this message in context: http://www.nabble.com/Declarative-Exception-Handling-in-ServiceMix-tf2161788.html#a6658179 Sent from the ServiceMix - Dev mailing list archive at Nabble.com. -- Cheers, Guillaume Nodet
Declarative Exception Handling in ServiceMix
Ralf Wunsch wrote: > > > We are starting a new EAI project. At this time ServiceMix is our choice > for the implementation plattform. We have strong requirements for > monitoring and control issues. At this one aspect is the handling of > unexpected errors. For this reason i have implemented the following error > handler solution. > > > > The error handling solution delegates errors or faults detected in > analysis of the MessageExchange objects to an ErrorHandler implemented as > XBean. This bean is used by an ErrorHandlerComponent (a JBI component > embedded in the flow) or by the JBIContainer (the centralized way) or > both. > > http://www.nabble.com/file/290/error-handler-embedding.png > > The ErrorHandler can cancel transactions and stop the container or the > source component (all cofigurable). Furthermore it's possible to route the > error or fault messages and the actuating message to a configurable > target. In this case ist possible to embed one or more > ErrorHandlerComponents into the flow. > > http://www.nabble.com/file/291/error-handler-flow.png > > Such an ambedded ErrorHandlerComponent borrowed by the EIP WireTap ensures > that the rerouted message from the source will be in a well know format > (the centralised approach can't accomplish this). The embedded and the > centralized approach can be used in combination. For synchronization the > ErrorHandlerComponent sets a Property on the outgoing MessageExchange and > the ErrorEventListener does nothing as long as this property can be found > in the MessageEchange which signals a fault or an error. > > > A sample configuration... > > > <bean id="errorHandler" > class="de.eval.eai.error.DefaultErrorHandler"> > </bean> > ... > <bean id="errorHandlerConfig" > class="de.eval.eai.error.ErrorHandlerConfig"> > <property name="shutdownOnFault" value="true" /> > <property name="rollbackOnFault" value="false" /> > </bean> > ... > <test:container id="jbi" >useMBeanServer="true" >createMBeanServer="false" >dumpStats="true" >statsInterval="10" >errorHandler="#errorHandler" >errorHandlerConfig="#errorHandlerConfig"> > ... > <sm:activationSpecs> > ... > <sm:activationSpec componentName="errorHandler"> > <sm:component> > <eai:component> > <eai:endpoints> > <eai:errorHandler service="errorHandler" > endpoint="endpoint"> > <eai:target> > <eai:exchange-target service="transformer" /> > </eai:target> > <eai:disqualifyTarget> > <eai:exchange-target service="failedQueue" /> > </eai:disqualifyTarget> > <eai:errorTarget> > <eai:exchange-target service="errorQueue" /> > </eai:errorTarget> > <eai:faultTarget> > <eai:exchange-target service="faultQueue" /> > </eai:faultTarget> > <property name="shutdownOnFault" value="true" /> > <property name="rollbackOnFault" value="false" /> > </eai:errorHandler> > </eai:endpoints> > </eai:component> > </sm:component> > </sm:activationSpec> > ... > > > Two questions: > > > Ist this a accurate ServieMix way (in accordance with the ideas of > ServiceMix)? > > > Is it on behalf of the project or the communitiy to reuse this solution? > > > Thanks, > Ralf Wunsch > > -- View this message in context: http://www.nabble.com/Declarative-Exception-Handling-in-ServiceMix-tf2161788.html#a6658179 Sent from the ServiceMix - Dev mailing list archive at Nabble.com.
Re: Declarative Exception Handling in ServiceMix
I Agree that I'm not sure you should build in exception routing when it is better placed as another component that handles the Call and return of an exception. It would seem that when building up services you should be handling exceptions and returning faults/exceptions in a clean fashion and that the routing of exceptions is better placed since I can see there becoming increasing details rquired for the routing. Just thinking of a SQLException and then needing the sqlCode in order to determine the "meaning" of the exception before routing. Philip On 8/25/06, Guillaume Nodet <[EMAIL PROTECTED]> wrote: I guess that if you want to handle exceptions in a JBI compliant way, you should put in the flow some specific components to do that. First, we need to make a distinction between faults and errors. Imho, faults are unrecoverable problems, due to the message itself. Errors are runtime problems, which may be able to be solved at a later time. In your example, depending on the reason why the data could not be stored in the database, the component should return a fault (if the data is corrupted) or an error (the database is down). In your use case, the error should be catched by a simple component (an EIP pattern) between the http component and the business component which would act as a normal proxy when no errors are reported, and redirect the flow elsewhere when an error occurs. Also, I don't really understand the "friendly error" concept ;) The http component is not designed to be a jsp server, so you won't have any nice interface there. The output should be an xml. If you want a nice interface, you should deploy a web app which would call the jbi bus and return a nice html page when an error occurs. Last, while I think declarative transactions may be really useful for POJO based components (servicemix-jsr181, or the yet to be defined new component, see other threads on the list), it would be difficult to apply it in a real JBI world. Let's discuss it, it' s just my thoughts. On 8/25/06, jpuro <[EMAIL PROTECTED]> wrote: > > > I think it would be useful to add declarative exception handling to > ServiceMix. The usefullness of such a feature can be seen from the > following simple use case involving a client submitting an order to a > fulfillment company: > > 1) The use case starts when the client sends an order to an HTTP endpoint > exposed in ServiceMix. The message representing the order is routed to a > business service component. > > 2) The business service component attempts to process the Order and save > it > to a database. However, an exception occurs during this process and gets > bubbled up. The fulfillment company would like to be notified via email > when an order fails to be processed. Since we have configured the > business > service component to pass all exceptions to an email component, the flow > moves to step 3. > > 3) The email component sends out an email notification to the fulfillment > company indicating that an error occurred while processing the order. > > 4) After the email has been sent out, the flow moves to another component > that returns a more user friendly error message to the original HTTP > endpoint. This way we do not send back a hard to read error message to > the > client. > > The purpose of such a flow is that we handle exceptions more gracefully > than > currently is supported by ServiceMix. Instead of bubbling up exceptions > to > the calling component, we should allow components to change the flow of a > message when an exception occurs. > > The configuration could look something like the following: > > service="example:businessService" > > exceptionDestionationService="example:emailService"> > > > > > > Alternatively, perhaps we can just use AOP to catch exceptions that occur > within a component: > > exceptionType="javax.jbi.messaging.MessagingException" > destinationService="example:emailService"> > > service="example:businessService"> > > > > > > > > > Here are a few concerns of mine: > > 1) The problem with the first example configuration is that it doesn't > allow you to get creative with how certain types of exceptions are > handled, > it just acts like a catch all. We may need to create a more flexible way > of > configuring exception handlin
