On Mon, May 4, 2009 at 11:40 AM, Zhi Zhou <[email protected]> wrote:
> Claus,
> Thank you very much for the quick response!
>
> On Mon, May 4, 2009 at 5:07 PM, Claus Ibsen <[email protected]> wrote:
>
>> Hi
>>
>> What version of Camel are you using? Camel 2.0 has many improvments in
>> error handling and processing over 1.x.
>>
>
> Sorry that I forgot to mention I am using 1.x for now as 2.0 is still going
> through milestone release stage.
>
>
>>
>> On Mon, May 4, 2009 at 10:54 AM, Zhi Zhou <[email protected]> wrote:
>> > Hello all,
>> >
>> > Camel's error handling is pretty powerful, but lately I am having two
>> > questions about it.
>> >
>> > 1) I am working a custom camel component, and not quite sure how to
>> handle
>> > certain error condition. I may be having wrong idea from the very
>> beginning
>> > but let me give you a simple scenario to describe the issue.
>> >
>> > from("jms:someQueue").to("myCustom:endpoint");
>> >
>> > My custom endpoint does some async message sending. For performance
>> reason,
>> > it should keep sending messages from the jms queue without waiting for
>> > responses. responses come back asynchronously from the remote host. The
>> > question here is that if a response doesn't return without a timeout
>> period,
>> > I would like an exception to be thrown and hence to be captured by
>> camel's
>> > error handling where some redelivery logic is made possible.
>> unfortunately,
>> > with this async nature of producing, the timeout event will be triggered
>> in
>> > a different thread and hence no way to have camel to capture my created
>> > exception up to my limited camel knowledge.
>> We are planning to add a new Async API in Camel 2.0 so you leverage
>> Camel to do async routing much more easily.
>>
>
>> Anyway if you leverage the async task execution in the JDK 1.5
>> concurrent API then you can get a handle to your async task, known as
>> a Future handle.
>> With that you can test whether the task is complete, get the result,
>> get the result within a timeout period etc.
>>
> Exactly I am using the concurrent API to implement a timeout task. but my
> headache is how to have camel informed of the exception that's created in my
> timeout task. it seems impossible to call any current 1.x API to align this
> timeout exception with the camel's standard error handling yet.
You can set an exception on the Exchange to indicate a timeout
exchange.setException(new ExchangeTimedOutException());
Or just set your own kind of time out exception.
Then Camel standard error handling will notice the exception and take
it from there.
>
> well look forward to the new Async API of 2.0. before having it on board, I
> probably still need to think of a solution.
>
>
>>
>> >
>> >
>> > 2) my second question: is it possible that the error handling will happen
>> in
>> > multiple threads in case of multi-threaded exchange processing. for
>> example,
>> > the following route:
>> >
>> > from("direct:start").thread(10).process(new Processor(){/*throw some
>> > exception*/});
>> >
>> > will the error handling happen in the same thread of the caller that
>> > produces message to "direct:start", or will happen concurrently in
>> multiple
>> > threads?
>> The thread is basically a worker pool, and since you use direct
>> component your route is synchronous all the way. Leveraging up till 10
>> worker threads.
>>
>> If you want to divide into async you should use the seda component.
>> But when you want to do request-reply over seda it gets complicated.
>>
>
> I am just wondering whether camel will spawn a thread for error handing or
> it's just using the current thread context. my above example might not be
> exactly what I wanted to show. Put it more straightforward, if I have an
> event-driven consumer, it typically does:
>
> getProcessor().process(exchange);
>
> to have the exchange consumed. in case of an exception ocurred down the
> route, camel's error handling will be sharing the same thread as the above
> call or executing in a separate thread? if it's the same thread, that means
> my event-driven consumer will be delayed until the exchange gets clear on
> exception.
>
>
>
>> Hence we are planning a new Async API in Camel 2.0 that addresses this.
>> There is a discussion on this in the camel-dev forum.
>>
>>
>> >
>> >
>> > Zhi
>> >
>>
>>
>>
>> --
>> Claus Ibsen
>> Apache Camel Committer
>>
>> Open Source Integration: http://fusesource.com
>> Blog: http://davsclaus.blogspot.com/
>> Twitter: http://twitter.com/davsclaus
>> Apache Camel Reference Card:
>> http://refcardz.dzone.com/refcardz/enterprise-integration
>>
>
--
Claus Ibsen
Apache Camel Committer
Open Source Integration: http://fusesource.com
Blog: http://davsclaus.blogspot.com/
Twitter: http://twitter.com/davsclaus
Apache Camel Reference Card:
http://refcardz.dzone.com/refcardz/enterprise-integration
