examples/cpp/broker.hpp

#ifndef BROKER_HPP
#define BROKER_HPP

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/// @file
///
/// Common code used by different broker examples.
///
/// The examples add functionality as needed, this helps to make it
/// easier to see the important differences between the examples.

#include "proton/event.hpp"
#include "proton/message.hpp"
#include "proton/handler.hpp"
#include "proton/sender.hpp"
#include "proton/transport.hpp"
#include "proton/url.hpp"

#include <iostream>
#include <deque>
#include <map>
#include <list>
#include <sstream>

/// A simple implementation of a queue.
class queue {
  public:
    queue(const std::string &name, bool dynamic = false) : name_(name), dynamic_(dynamic) {}

    std::string name() const { return name_; }

    void subscribe(proton::sender s) {
        consumers_.push_back(s);
    }

    // Return true if queue can be deleted.
    bool unsubscribe(proton::sender s) {
        consumers_.remove(s);
        return (consumers_.size() == 0 && (dynamic_ || messages_.size() == 0));
    }

    void publish(const proton::message &m, proton::receiver r) {
        messages_.push_back(m);
        dispatch(0);
    }

    void dispatch(proton::sender *s) {
        while (deliver_to(s)) {}
    }

    bool deliver_to(proton::sender *s) {
        // Deliver to single sender if supplied, else all consumers
        int count = s ? 1 : consumers_.size();

        if (!count) return false;

        bool result = false;
        sender_list::iterator it = consumers_.begin();

        if (!s && count) {
            s = &*it;
        }
            
        while (messages_.size()) {
            if (s->credit()) {
                const proton::message& m = messages_.front();

                s->send(m);
                messages_.pop_front();
                result = true;
            }
            
            if (--count) {
                it++;
            } else {
                return result;
            }
        }
        
        return false;
    }

  private:
    typedef std::deque<proton::message> message_queue;
    typedef std::list<proton::sender> sender_list;

    std::string name_;
    bool dynamic_;
    message_queue messages_;
    sender_list consumers_;
};

/// A collection of queues and queue factory, used by a broker.
class queues {
  public:
    queues() : next_id_(0) {}

    // Get or create a queue.
    virtual queue &get(const std::string &address = std::string()) {
        if (address.empty()) {
            throw std::runtime_error("empty queue name");
        }

        queue*& q = queues_[address];

        if (!q) q = new queue(address);

        return *q;
    }

    // Create a dynamic queue with a unique name.
    virtual queue &dynamic() {
        std::ostringstream os;
        os << "q" << next_id_++;
        queue *q = queues_[os.str()] = new queue(os.str(), true);

        return *q;
    }

    // Delete the named queue
    virtual void erase(std::string &name) {
        delete queues_[name];
        queues_.erase(name);
    }

  protected:
    typedef std::map<std::string, queue *> queue_map;
    queue_map queues_;
    uint64_t next_id_; // Use to generate unique queue IDs.
};


/** Common handler logic for brokers. */
class broker_handler : public proton::handler {
  public:
    broker_handler(queues& qs) : queues_(qs) {}

    void on_link_open(proton::event &e) {
        proton::link lnk = e.link();

        if (!!lnk.sender()) {
            proton::terminus remote_source(lnk.remote_source());
            queue &q = remote_source.dynamic() ?
                queues_.dynamic() : queues_.get(remote_source.address());
            lnk.local_source().address(q.name());

            q.subscribe(lnk.sender());
            std::cout << "broker outgoing link from " << q.name() << std::endl;
        } else {
            // Receiver
            std::string address = lnk.remote_target().address();
            if (!address.empty()) {
                lnk.local_target().address(address);
                std::cout << "broker incoming link to " << address << std::endl;
            }
        }
    }

    void unsubscribe(proton::sender lnk) {
        std::string address = lnk.local_source().address();

        if (queues_.get(address).unsubscribe(lnk)) {
            queues_.erase(address);
        }
    }

    void on_link_close(proton::event &e) {
        proton::link lnk = e.link();

        if (!!lnk.sender()) {
            unsubscribe(lnk.sender());
        }
    }

    void on_connection_close(proton::event &e) {
        remove_stale_consumers(e.connection());
    }

    void on_transport_close(proton::event &e) {
        remove_stale_consumers(e.connection());
    }

    void on_transport_error(proton::event &e) {
        std::cout << "broker client disconnect: " << e.transport().condition().str() << std::endl;
    }

    void on_unhandled_error(proton::event &e, const proton::condition &c) {
        std::cerr << "broker error: " << e.name() << ":" << c.str() << std::endl;
    }

    void remove_stale_consumers(proton::connection connection) {
        proton::link_range r = connection.find_links(proton::endpoint::REMOTE_ACTIVE);

        for (proton::link_iterator l = r.begin(); l != r.end(); ++l) {
            if (!!l->sender()) {
                unsubscribe(l->sender());
            }
        }
    }

    void on_sendable(proton::event &e) {
        proton::link lnk = e.link();
        std::string address = lnk.local_source().address();
        proton::sender s = lnk.sender();

        queues_.get(address).dispatch(&s);
    }

    void on_message(proton::event &e) {
        std::string address = e.link().local_target().address();
        
        queues_.get(address).publish(e.message(), e.link().receiver());
    }

  protected:
    queues& queues_;
};

#endif // BROKER_HPP