Qpid Proton C++ API  0.18.1
multithreaded_client.cpp

A multithreaded sender and receiver.Requires C++11

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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
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//
// C++11 or greater
//
// A multi-threaded client that calls proton::container::run() in one thread, sends
// messages in another and receives messages in a third.
//
// Note this client does not deal with flow-control. If the sender is faster
// than the receiver, messages will build up in memory on the sending side.
// See @ref multithreaded_client_flow_control.cpp for a more complex example with
// flow control.
//
// NOTE: no proper error handling
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <queue>
#include <sstream>
#include <string>
#include <thread>
// Lock output from threads to avoid scramblin
std::mutex out_lock;
#define OUT(x) do { std::lock_guard<std::mutex> l(out_lock); x; } while (false)
// Handler for a single thread-safe sending and receiving connection.
class client : public proton::messaging_handler {
// Invariant
const std::string url_;
const std::string address_;
// Only used in proton handler thread
proton::sender sender_;
// Shared by proton and user threads, protected by lock_
std::mutex lock_;
proton::work_queue *work_queue_;
std::condition_variable sender_ready_;
std::queue<proton::message> messages_;
std::condition_variable messages_ready_;
public:
client(const std::string& url, const std::string& address) : url_(url), address_(address), work_queue_(0) {}
// Thread safe
void send(const proton::message& msg) {
// Use [=] to copy the message, we cannot pass it by reference since it
// will be used in another thread.
work_queue()->add([=]() { sender_.send(msg); });
}
// Thread safe
proton::message receive() {
std::unique_lock<std::mutex> l(lock_);
while (messages_.empty()) messages_ready_.wait(l);
auto msg = std::move(messages_.front());
messages_.pop();
return msg;
}
// Thread safe
void close() {
work_queue()->add([=]() { sender_.connection().close(); });
}
private:
proton::work_queue* work_queue() {
// Wait till work_queue_ and sender_ are initialized.
std::unique_lock<std::mutex> l(lock_);
while (!work_queue_) sender_ready_.wait(l);
return work_queue_;
}
// == messaging_handler overrides, only called in proton hander thread
// Note: this example creates a connection when the container starts.
// To create connections after the container has started, use
// container::connect().
// See @ref multithreaded_client_flow_control.cpp for an example.
void on_container_start(proton::container& cont) override {
cont.connect(url_);
}
void on_connection_open(proton::connection& conn) override {
conn.open_sender(address_);
conn.open_receiver(address_);
}
void on_sender_open(proton::sender& s) override {
// sender_ and work_queue_ must be set atomically
std::lock_guard<std::mutex> l(lock_);
sender_ = s;
work_queue_ = &s.work_queue();
sender_ready_.notify_all();
}
void on_message(proton::delivery& dlv, proton::message& msg) override {
std::lock_guard<std::mutex> l(lock_);
messages_.push(msg);
messages_ready_.notify_all();
}
void on_error(const proton::error_condition& e) override {
OUT(std::cerr << "unexpected error: " << e << std::endl);
exit(1);
}
};
int main(int argc, const char** argv) {
try {
if (argc != 4) {
std ::cerr <<
"Usage: " << argv[0] << " CONNECTION-URL AMQP-ADDRESS MESSAGE-COUNT\n"
"CONNECTION-URL: connection address, e.g.'amqp://127.0.0.1'\n"
"AMQP-ADDRESS: AMQP node address, e.g. 'examples'\n"
"MESSAGE-COUNT: number of messages to send\n";
return 1;
}
const char *url = argv[1];
const char *address = argv[2];
int n_messages = atoi(argv[3]);
client cl(url, address);
proton::container container(cl);
std::thread container_thread([&]() { container.run(); });
std::thread sender([&]() {
for (int i = 0; i < n_messages; ++i) {
cl.send(msg);
OUT(std::cout << "sent \"" << msg.body() << '"' << std::endl);
}
});
int received = 0;
std::thread receiver([&]() {
for (int i = 0; i < n_messages; ++i) {
auto msg = cl.receive();
OUT(std::cout << "received \"" << msg.body() << '"' << std::endl);
++received;
}
});
sender.join();
receiver.join();
cl.close();
container_thread.join();
std::cout << received << " messages sent and received" << std::endl;
return 0;
} catch (const std::exception& e) {
std::cerr << e.what() << std::endl;
}
return 1;
}