On 07/23/2015 12:58 PM, Andreas Welchlin wrote:
Hello,
since there seems to be no method in the C++ messaging API to listen on
two different message brokers at the same time I will do this using two
additional threads. So I ask myself how threadsafe the messaging API is
or more concrete: how threadsafe the method
"qpid::messaging::Session::nextReceiver()" is.
My plan is to use the main thread to read and send messages from/to both
of the brokers.
For waiting on incoming messages I start two additional threads. Each of
them calls Session::nextReceiver(). If a message is available the main
thread will be informed and call fetch() on the receiver which woke up.
My question is: Would it be a problem if one thread calls
session.nextReceiver() and at the same time another thread calls
receiver.fetch()?
The Session::nextReceiver() method returns the next receiver on which a
fetch would be successful. If you call this again concurrently with
actually calling the Receiver::fetch(), there is a race. The
nextReceiver call may get the same receiver again simply because it gets
in before the fetch.
It could also be possible that the main thread calls sender.send() while
the other thread is waiting in session.nextReceiver()?
This should cause no problems.
On 07/21/2015 10:15 AM, Andreas Welchlin wrote:
I wrote an application which reads from two different message brokers.
So I used two connections and therefore I got also two sessions.
When I have just one session I can just call
"qpid::messaging::Session::nextReceiver()". But this is not possible
with two sessions. I could call nextReceiver for both sessions in two
differnt threads but this is not so nice.
Do you have an idea how I could solve this in an easy way?
This is a gap/failing of the qpid::messaging API. Though I did spend
some time investigating changes to eliminate it, my own view at present
is that the emerging proton based reactive API in c++[1] is probably
the better solution. Alan has created some nice documentation for that:
http://people.apache.org/~aconway/proton/index.html (it is AMQP 1.0 only
as well, I should note).
[1] currently still on a branch but ready I believe to be meregd as soon
as 0.10 is released:
https://git-wip-us.apache.org/repos/asf?p=qpid-proton.git;a=shortlog;h=refs/heads/cjansen-cpp-client
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