Dear all,
I'm experiencing some issues in writing an AMQP client with Qpid Proton C++.
My client should only send messages to a particular queue on an ActiveMQ
broker and it is not supposed to receive any message over that connection.
The client should not send the messages as soon as it is started (with
"proton::container(AMQP_client).run();"), but it should wait for the data
to be provided by an external thread, which may become available even after
some minutes (I cannot tell in advance when the data will be available, and
there may be even a long time between two consecutive chunks of available
data).
If I try to supply the AMQP client loop with new data through a pipe (on
which data is written by the external thread), I can write an "AMQP_client"
class like the following:
void AMQP_client::on_container_start(proton::container& c) {
c.connect(broker_address);
}
void AMQP_client::on_connection_open(proton::connection& c) {
c.open_sender(queue_name);
}
void AMQP_client::on_sendable(proton::sender &s) {
uint8_t buffer[1024];
int bufsize;
proton::message amqp_msg;
// Wait for new data to be sent (wait for data to be written on the
pipe)
if((bufsize=read(pipe_read_end,&buffer,1024))==-1) {
perror("read() error");
return;
}
amqp_msg.body(proton::binary(buffer,buffer+bufsize));
s.send(amqp_msg);
}
In this case, however, "on_sendable" blocks on the read() operation and, if
the data becomes available few minutes after, the broker closes the
connection as the client loop is completely blocked and cannot even send
the heartbeat messages.
If, instead, I do not block on the read() operation (for instance I read()
with a timeout, by using poll()), "on_sendable" is triggered only once and
I cannot find any other event to trigger the transmission of a message when
data becomes available.
I know that, in Python, I could solve this issue for instance by relying on
"EventInjector", but I'm unable to find a similar solution with the C++
version of the library (I would prefer to stick with C++, in this case, and
not to fall back to Qpid Proton C).
Do you know how I can solve this problem? Is there a way to "inject"
external aperiodic events/data to be sent via AMQP?
Thank you very much in advance,
Francesco Raviglione
