On 08/10/14 08:16, xavier wrote:
Hi Frase,
Thanks for your explanation, but here, my code:
In the requester:
char * corrId;
.....
.....
pn_bytes_t bytes = pn_bytes(correlationId.size(), corrId);
pn_atom_t id;
id.type = PN_STRING;
id.u.as_bytes = bytes;
pn_message_set_correlation_id(message, id);
and after, send it
pn_messenger_put(messengerProducer, message);
I see on the broker, the correlationId is correctly setted, so no pb.
after I wait the answer, but I would like (like JMS) only wake up on an
answer at my question (and the correlationId is here to do that)
in CMS
MessageConsumer* consumer = session->createConsumer(destination,
"JMSCorrelationID='" + correlationId + "'");
consumer->start();
But with qpid proton and messenger, if I do that:
I get the response, and I does not accept it, if the correlationId recieve,
is not the good one, but for me, it's not a good practice, because we
retrieve the message (network traffic) in right case, but in wrong case too.
So I would like to the same things like CMS, but.... how????
pn_selectable_t ??????????
pn_selector_t ????????????
Thank you
Xav
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Re:
MessageConsumer* consumer = session->createConsumer(destination,
"JMSCorrelationID='" + correlationId + "'");
consumer->start();
That's exactly the bit that I've been trying to explain is the complicated bit,
and the bit that Robbie referred to in his previous reply.
In JMS and I guess with CMS that syntax means:
| MessageConsumer
<http://docs.oracle.com/javaee/5/api/javax/jms/MessageConsumer.html>|
|*createConsumer
<http://docs.oracle.com/javaee/5/api/javax/jms/Session.html#createConsumer%28javax.jms.Destination,%20java.lang.String,%20boolean%29>*(Destination
<http://docs.oracle.com/javaee/5/api/javax/jms/Destination.html> destination,
String
<http://java.sun.com/j2se/1.5/docs/api/java/lang/String.html> messageSelector,
boolean NoLocal)|
Creates|MessageConsumer| for the specified destination, using a
message selector.
At an API level it's nice and simple, but there's a lot going on under the hood
and what it's doing is to pass information on the AMQP link attach (I think)
that configures a Message Selector (which is and AMQP filter
https://svn.apache.org/repos/asf/qpid/trunk/qpid/specs/apache-filters.xml#type-selector-filter).
Unfortunately (and I'd agree somewhat annoyingly!!) proton Messenger does not
yet support this type of sophistication when specifying subscriptions, I wish
it did myself, but unfortunately it currently does not :-(
The stuff:
pn_selectable_t ??????????
pn_selector_t ????????????
Relates to something completely different I'm afraid those are actually related
to low level socket selectors (i.e. more related to the select/poll/epoll
system calls than Message Selectors). Their main use is for replacing
Messenger's internal network event loop so it can be more easily integrated
with other applications.
I can't recall why you said you were using Messenger specifically, If you can
use C++ (rather than C) you might want to look at the qpid::messaging API, you
can definitely do the sort of thing that you want (e.g. using the broker to
perform filtering based on CorrelationID) using qpid::messaging. The syntax is
a little different in that I don't believe that there's a particular overloaded
createConsumer method call to set a selector and you'd have to do it in the
Address String - it'd look *something* like the following (I think, I've not
tried it YMMV) BTW if you haven't come across it drain is a little qpid demo
application that's really useful for trying out Address Strings. So if you have
a queue called queue1 this should filter on messages with a given correlation
ID.
./drain -b localhost -f \
"queue1; {create: receiver, link: {name: test-link, selector:
\"correlation_id='<mycid>'\"}}"
That's the sort of syntax I'd like to see supported for Messenger Subscriptions
too (but as I say it currently isn't).
I've copied my response to the qpid users mailing list, I tend to recommend
that people post questions there as it tends to have a broader readership than
the proton one.
If you have to use C (as opposed to C++) then as I say Messenger won't do what
you want (though clearly you could do your own filtering inside your
consumer/server client), you could also get a bit more low-level and use the
Engine API, which will allow the sort of thing that you want (qpid::messaging
actually uses the proton Engine API under the hood), but I'm afraid that I
couldn't help you make any progress using Engine as I've not got round to
playing with that myself yet.
Sorry I can't give you a simple answer to your question, hopefully my
explanation of the reasons why is better than it was previously.
In short:
* You can't currently do message selectors/filters with Messenger
* You can do this with JMS and qpid::messaging but the latter is C++ not C
* You can do it with the Engine API, but I couldn't tell you how to (if you
look in the qpid::messaging source you should get a good idea - that's where
I'd start)
Regards,
Frase
