Qpid Proton C++ API  0.18.1
scheduled_send.cpp

Shows how to use proton::container::schedule to schedule a timed callback.This version uses std::function and so requires C++11 or better. For a C++03 compatible approach see scheduled_send_03.cpp.

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#include "options.hpp"
#include <iostream>
#include "fake_cpp11.hpp"
// Send messages at a constant rate one per interval. cancel after a timeout.
class scheduled_sender : public proton::messaging_handler {
private:
std::string url;
proton::duration interval, timeout;
proton::work_queue* work_queue;
bool ready, canceled;
public:
scheduled_sender(const std::string &s, double d, double t) :
url(s),
interval(int(d*proton::duration::SECOND.milliseconds())), // Send interval.
timeout(int(t*proton::duration::SECOND.milliseconds())), // Cancel after timeout.
work_queue(0),
ready(true), // Ready to send.
canceled(false) // Canceled.
{}
// The awkward looking double lambda is necessary because the scheduled lambdas run in the container context
// and must arrange lambdas for send and close to happen in the connection context.
c.open_sender(url);
}
void on_sender_open(proton::sender &s) OVERRIDE {
sender = s;
work_queue = &s.work_queue();
// Call this->cancel after timeout.
s.container().schedule(timeout, [this]() { this->work_queue->add( [this]() { this->cancel(); }); });
// Start regular ticks every interval.
s.container().schedule(interval, [this]() { this->work_queue->add( [this]() { this->tick(); }); });
}
void cancel() {
canceled = true;
sender.connection().close();
}
void tick() {
// Schedule the next tick unless we have been cancelled.
if (!canceled)
sender.container().schedule(interval, [this]() { this->work_queue->add( [this]() { this->tick(); }); });
if (sender.credit() > 0) // Only send if we have credit
send();
else
ready = true; // Set the ready flag, send as soon as we get credit.
}
void on_sendable(proton::sender &) OVERRIDE {
if (ready) // We have been ticked since the last send.
send();
}
void send() {
std::cout << "send" << std::endl;
sender.send(proton::message("ping"));
ready = false;
}
};
int main(int argc, char **argv) {
std::string address("127.0.0.1:5672/examples");
double interval = 1.0;
double timeout = 5.0;
example::options opts(argc, argv);
opts.add_value(address, 'a', "address", "connect and send to URL", "URL");
opts.add_value(interval, 'i', "interval", "send a message every INTERVAL seconds", "INTERVAL");
opts.add_value(timeout, 't', "timeout", "stop after T seconds", "T");
try {
opts.parse();
scheduled_sender h(address, interval, timeout);
return 0;
} catch (const example::bad_option& e) {
std::cout << opts << std::endl << e.what() << std::endl;
} catch (const std::exception& e) {
std::cerr << e.what() << std::endl;
}
return 1;
}