| |
| <h1>multithreaded_client_flow_control.cpp</h1> |
| <div class="highlight"><pre><span></span><span class="c1">//</span> |
| <span class="c1">// C++11 or greater</span> |
| <span class="c1">//</span> |
| <span class="c1">// A multi-threaded client that sends and receives messages from multiple AMQP</span> |
| <span class="c1">// addresses.</span> |
| <span class="c1">//</span> |
| <span class="c1">// Demonstrates how to:</span> |
| <span class="c1">//</span> |
| <span class="c1">// - implement proton handlers that interact with user threads safely</span> |
| <span class="c1">// - block sender threads to respect AMQP flow control</span> |
| <span class="c1">// - use AMQP flow control to limit message buffering for receivers threads</span> |
| <span class="c1">//</span> |
| <span class="c1">// We define sender and receiver classes with simple, thread-safe blocking</span> |
| <span class="c1">// send() and receive() functions.</span> |
| <span class="c1">//</span> |
| <span class="c1">// These classes are also privately proton::message_handler instances. They use</span> |
| <span class="c1">// the thread-safe proton::work_queue and standard C++ synchronization (std::mutex</span> |
| <span class="c1">// etc.) to pass messages between user and proton::container threads.</span> |
| <span class="c1">//</span> |
| <span class="c1">// NOTE: no proper error handling</span> |
| |
| <span class="cp">#include</span> <span class="cpf"><proton/connection.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/connection_options.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/container.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/message.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/messaging_handler.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/receiver.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/receiver_options.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/sender.hpp></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><proton/work_queue.hpp></span><span class="cp"></span> |
| |
| <span class="cp">#include</span> <span class="cpf"><atomic></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><condition_variable></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><iostream></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><mutex></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><queue></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><sstream></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><string></span><span class="cp"></span> |
| <span class="cp">#include</span> <span class="cpf"><thread></span><span class="cp"></span> |
| |
| <span class="c1">// Lock output from threads to avoid scrambling</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">mutex</span> <span class="n">out_lock</span><span class="p">;</span> |
| <span class="cp">#define OUT(x) do { std::lock_guard<std::mutex> l(out_lock); x; } while (false)</span> |
| |
| <span class="c1">// Exception raised if a sender or receiver is closed when trying to send/receive</span> |
| <span class="k">class</span> <span class="nc">closed</span> <span class="o">:</span> <span class="k">public</span> <span class="n">std</span><span class="o">::</span><span class="n">runtime_error</span> <span class="p">{</span> |
| <span class="k">public</span><span class="o">:</span> |
| <span class="n">closed</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">msg</span><span class="p">)</span> <span class="o">:</span> <span class="n">std</span><span class="o">::</span><span class="n">runtime_error</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span> <span class="p">{}</span> |
| <span class="p">};</span> |
| |
| <span class="c1">// A thread-safe sending connection that blocks sending threads when there</span> |
| <span class="c1">// is no AMQP credit to send messages.</span> |
| <span class="k">class</span> <span class="nc">sender</span> <span class="o">:</span> <span class="k">private</span> <span class="n">proton</span><span class="o">::</span><span class="n">messaging_handler</span> <span class="p">{</span> |
| <span class="c1">// Only used in proton handler thread</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">sender</span> <span class="n">sender_</span><span class="p">;</span> |
| |
| <span class="c1">// Shared by proton and user threads, protected by lock_</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">mutex</span> <span class="n">lock_</span><span class="p">;</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">work_queue</span> <span class="o">*</span><span class="n">work_queue_</span><span class="p">;</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">condition_variable</span> <span class="n">sender_ready_</span><span class="p">;</span> |
| <span class="kt">int</span> <span class="n">queued_</span><span class="p">;</span> <span class="c1">// Queued messages waiting to be sent</span> |
| <span class="kt">int</span> <span class="n">credit_</span><span class="p">;</span> <span class="c1">// AMQP credit - number of messages we can send</span> |
| |
| <span class="k">public</span><span class="o">:</span> |
| <span class="n">sender</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">container</span><span class="o">&</span> <span class="n">cont</span><span class="p">,</span> <span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">url</span><span class="p">,</span> <span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">address</span><span class="p">)</span> |
| <span class="o">:</span> <span class="n">work_queue_</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span> <span class="n">queued_</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span> <span class="n">credit_</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="n">cont</span><span class="p">.</span><span class="n">open_sender</span><span class="p">(</span><span class="n">url</span><span class="o">+</span><span class="s">"/"</span><span class="o">+</span><span class="n">address</span><span class="p">,</span> <span class="n">proton</span><span class="o">::</span><span class="n">connection_options</span><span class="p">().</span><span class="n">handler</span><span class="p">(</span><span class="o">*</span><span class="k">this</span><span class="p">));</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// Thread safe</span> |
| <span class="kt">void</span> <span class="n">send</span><span class="p">(</span><span class="k">const</span> <span class="n">proton</span><span class="o">::</span><span class="n">message</span><span class="o">&</span> <span class="n">m</span><span class="p">)</span> <span class="p">{</span> |
| <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">unique_lock</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="c1">// Don't queue up more messages than we have credit for</span> |
| <span class="k">while</span> <span class="p">(</span><span class="o">!</span><span class="n">work_queue_</span> <span class="o">||</span> <span class="n">queued_</span> <span class="o">>=</span> <span class="n">credit_</span><span class="p">)</span> <span class="n">sender_ready_</span><span class="p">.</span><span class="n">wait</span><span class="p">(</span><span class="n">l</span><span class="p">);</span> |
| <span class="o">++</span><span class="n">queued_</span><span class="p">;</span> |
| <span class="p">}</span> |
| <span class="n">work_queue_</span><span class="o">-></span><span class="n">add</span><span class="p">([</span><span class="o">=</span><span class="p">]()</span> <span class="p">{</span> <span class="k">this</span><span class="o">-></span><span class="n">do_send</span><span class="p">(</span><span class="n">m</span><span class="p">);</span> <span class="p">});</span> <span class="c1">// work_queue_ is thread safe</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// Thread safe</span> |
| <span class="kt">void</span> <span class="n">close</span><span class="p">()</span> <span class="p">{</span> |
| <span class="n">work_queue</span><span class="p">()</span><span class="o">-></span><span class="n">add</span><span class="p">([</span><span class="o">=</span><span class="p">]()</span> <span class="p">{</span> <span class="n">sender_</span><span class="p">.</span><span class="n">connection</span><span class="p">().</span><span class="n">close</span><span class="p">();</span> <span class="p">});</span> |
| <span class="p">}</span> |
| |
| <span class="k">private</span><span class="o">:</span> |
| |
| <span class="n">proton</span><span class="o">::</span><span class="n">work_queue</span><span class="o">*</span> <span class="n">work_queue</span><span class="p">()</span> <span class="p">{</span> |
| <span class="c1">// Wait till work_queue_ and sender_ are initialized.</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">unique_lock</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="k">while</span> <span class="p">(</span><span class="o">!</span><span class="n">work_queue_</span><span class="p">)</span> <span class="n">sender_ready_</span><span class="p">.</span><span class="n">wait</span><span class="p">(</span><span class="n">l</span><span class="p">);</span> |
| <span class="k">return</span> <span class="n">work_queue_</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// == messaging_handler overrides, only called in proton handler thread</span> |
| |
| <span class="kt">void</span> <span class="n">on_sender_open</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">sender</span><span class="o">&</span> <span class="n">s</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="c1">// Make sure sender_ and work_queue_ are set atomically</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="n">sender_</span> <span class="o">=</span> <span class="n">s</span><span class="p">;</span> |
| <span class="n">work_queue_</span> <span class="o">=</span> <span class="o">&</span><span class="n">s</span><span class="p">.</span><span class="n">work_queue</span><span class="p">();</span> |
| <span class="p">}</span> |
| |
| <span class="kt">void</span> <span class="n">on_sendable</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">sender</span><span class="o">&</span> <span class="n">s</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="n">credit_</span> <span class="o">=</span> <span class="n">s</span><span class="p">.</span><span class="n">credit</span><span class="p">();</span> |
| <span class="n">sender_ready_</span><span class="p">.</span><span class="n">notify_all</span><span class="p">();</span> <span class="c1">// Notify senders we have credit</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// work_queue work items is are automatically dequeued and called by proton</span> |
| <span class="c1">// This function is called because it was queued by send()</span> |
| <span class="kt">void</span> <span class="n">do_send</span><span class="p">(</span><span class="k">const</span> <span class="n">proton</span><span class="o">::</span><span class="n">message</span><span class="o">&</span> <span class="n">m</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">sender_</span><span class="p">.</span><span class="n">send</span><span class="p">(</span><span class="n">m</span><span class="p">);</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="o">--</span><span class="n">queued_</span><span class="p">;</span> <span class="c1">// work item was consumed from the work_queue</span> |
| <span class="n">credit_</span> <span class="o">=</span> <span class="n">sender_</span><span class="p">.</span><span class="n">credit</span><span class="p">();</span> <span class="c1">// update credit</span> |
| <span class="n">sender_ready_</span><span class="p">.</span><span class="n">notify_all</span><span class="p">();</span> <span class="c1">// Notify senders we have space on queue</span> |
| <span class="p">}</span> |
| |
| <span class="kt">void</span> <span class="n">on_error</span><span class="p">(</span><span class="k">const</span> <span class="n">proton</span><span class="o">::</span><span class="n">error_condition</span><span class="o">&</span> <span class="n">e</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> <span class="s">"unexpected error: "</span> <span class="o"><<</span> <span class="n">e</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="p">};</span> |
| |
| <span class="c1">// A thread safe receiving connection that blocks receiving threads when there</span> |
| <span class="c1">// are no messages available, and maintains a bounded buffer of incoming</span> |
| <span class="c1">// messages by issuing AMQP credit only when there is space in the buffer.</span> |
| <span class="k">class</span> <span class="nc">receiver</span> <span class="o">:</span> <span class="k">private</span> <span class="n">proton</span><span class="o">::</span><span class="n">messaging_handler</span> <span class="p">{</span> |
| <span class="k">static</span> <span class="k">const</span> <span class="kt">size_t</span> <span class="n">MAX_BUFFER</span> <span class="o">=</span> <span class="mi">100</span><span class="p">;</span> <span class="c1">// Max number of buffered messages</span> |
| |
| <span class="c1">// Used in proton threads only</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">receiver</span> <span class="n">receiver_</span><span class="p">;</span> |
| |
| <span class="c1">// Used in proton and user threads, protected by lock_</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">mutex</span> <span class="n">lock_</span><span class="p">;</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">work_queue</span><span class="o">*</span> <span class="n">work_queue_</span><span class="p">;</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">queue</span><span class="o"><</span><span class="n">proton</span><span class="o">::</span><span class="n">message</span><span class="o">></span> <span class="n">buffer_</span><span class="p">;</span> <span class="c1">// Messages not yet returned by receive()</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">condition_variable</span> <span class="n">can_receive_</span><span class="p">;</span> <span class="c1">// Notify receivers of messages</span> |
| <span class="kt">bool</span> <span class="n">closed_</span><span class="p">;</span> |
| |
| <span class="k">public</span><span class="o">:</span> |
| |
| <span class="c1">// Connect to url</span> |
| <span class="n">receiver</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">container</span><span class="o">&</span> <span class="n">cont</span><span class="p">,</span> <span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">url</span><span class="p">,</span> <span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">address</span><span class="p">)</span> |
| <span class="o">:</span> <span class="n">work_queue_</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span> <span class="n">closed_</span><span class="p">(</span><span class="nb">false</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="c1">// NOTE:credit_window(0) disables automatic flow control.</span> |
| <span class="c1">// We will use flow control to match AMQP credit to buffer capacity.</span> |
| <span class="n">cont</span><span class="p">.</span><span class="n">open_receiver</span><span class="p">(</span><span class="n">url</span><span class="o">+</span><span class="s">"/"</span><span class="o">+</span><span class="n">address</span><span class="p">,</span> <span class="n">proton</span><span class="o">::</span><span class="n">receiver_options</span><span class="p">().</span><span class="n">credit_window</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">connection_options</span><span class="p">().</span><span class="n">handler</span><span class="p">(</span><span class="o">*</span><span class="k">this</span><span class="p">));</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// Thread safe receive</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">message</span> <span class="n">receive</span><span class="p">()</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">unique_lock</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="c1">// Wait for buffered messages</span> |
| <span class="k">while</span> <span class="p">(</span><span class="o">!</span><span class="n">closed_</span> <span class="o">&&</span> <span class="p">(</span><span class="o">!</span><span class="n">work_queue_</span> <span class="o">||</span> <span class="n">buffer_</span><span class="p">.</span><span class="n">empty</span><span class="p">()))</span> <span class="p">{</span> |
| <span class="n">can_receive_</span><span class="p">.</span><span class="n">wait</span><span class="p">(</span><span class="n">l</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="k">if</span> <span class="p">(</span><span class="n">closed_</span><span class="p">)</span> <span class="k">throw</span> <span class="n">closed</span><span class="p">(</span><span class="s">"receiver closed"</span><span class="p">);</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">message</span> <span class="n">m</span> <span class="o">=</span> <span class="n">std</span><span class="o">::</span><span class="n">move</span><span class="p">(</span><span class="n">buffer_</span><span class="p">.</span><span class="n">front</span><span class="p">());</span> |
| <span class="n">buffer_</span><span class="p">.</span><span class="n">pop</span><span class="p">();</span> |
| <span class="c1">// Add a lambda to the work queue to call receive_done().</span> |
| <span class="c1">// This will tell the handler to add more credit.</span> |
| <span class="n">work_queue_</span><span class="o">-></span><span class="n">add</span><span class="p">([</span><span class="o">=</span><span class="p">]()</span> <span class="p">{</span> <span class="k">this</span><span class="o">-></span><span class="n">receive_done</span><span class="p">();</span> <span class="p">});</span> |
| <span class="k">return</span> <span class="n">m</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// Thread safe</span> |
| <span class="kt">void</span> <span class="n">close</span><span class="p">()</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">closed_</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">closed_</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span> |
| <span class="n">can_receive_</span><span class="p">.</span><span class="n">notify_all</span><span class="p">();</span> |
| <span class="k">if</span> <span class="p">(</span><span class="n">work_queue_</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">work_queue_</span><span class="o">-></span><span class="n">add</span><span class="p">([</span><span class="k">this</span><span class="p">]()</span> <span class="p">{</span> <span class="k">this</span><span class="o">-></span><span class="n">receiver_</span><span class="p">.</span><span class="n">connection</span><span class="p">().</span><span class="n">close</span><span class="p">();</span> <span class="p">});</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| <span class="k">private</span><span class="o">:</span> |
| <span class="c1">// ==== The following are called by proton threads only.</span> |
| |
| <span class="kt">void</span> <span class="n">on_receiver_open</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">receiver</span><span class="o">&</span> <span class="n">r</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="n">receiver_</span> <span class="o">=</span> <span class="n">r</span><span class="p">;</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="n">work_queue_</span> <span class="o">=</span> <span class="o">&</span><span class="n">receiver_</span><span class="p">.</span><span class="n">work_queue</span><span class="p">();</span> |
| <span class="n">receiver_</span><span class="p">.</span><span class="n">add_credit</span><span class="p">(</span><span class="n">MAX_BUFFER</span><span class="p">);</span> <span class="c1">// Buffer is empty, initial credit is the limit</span> |
| <span class="p">}</span> |
| |
| <span class="kt">void</span> <span class="n">on_message</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">delivery</span> <span class="o">&</span><span class="n">d</span><span class="p">,</span> <span class="n">proton</span><span class="o">::</span><span class="n">message</span> <span class="o">&</span><span class="n">m</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="c1">// Proton automatically reduces credit by 1 before calling on_message</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">lock_guard</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">mutex</span><span class="o">></span> <span class="n">l</span><span class="p">(</span><span class="n">lock_</span><span class="p">);</span> |
| <span class="n">buffer_</span><span class="p">.</span><span class="n">push</span><span class="p">(</span><span class="n">m</span><span class="p">);</span> |
| <span class="n">can_receive_</span><span class="p">.</span><span class="n">notify_all</span><span class="p">();</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// called via work_queue</span> |
| <span class="kt">void</span> <span class="n">receive_done</span><span class="p">()</span> <span class="p">{</span> |
| <span class="c1">// Add 1 credit, a receiver has taken a message out of the buffer.</span> |
| <span class="n">receiver_</span><span class="p">.</span><span class="n">add_credit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="p">}</span> |
| |
| <span class="kt">void</span> <span class="n">on_error</span><span class="p">(</span><span class="k">const</span> <span class="n">proton</span><span class="o">::</span><span class="n">error_condition</span><span class="o">&</span> <span class="n">e</span><span class="p">)</span> <span class="k">override</span> <span class="p">{</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> <span class="s">"unexpected error: "</span> <span class="o"><<</span> <span class="n">e</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="p">};</span> |
| |
| <span class="c1">// ==== Example code using the sender and receiver</span> |
| |
| <span class="c1">// Send n messages</span> |
| <span class="kt">void</span> <span class="nf">send_thread</span><span class="p">(</span><span class="n">sender</span><span class="o">&</span> <span class="n">s</span><span class="p">,</span> <span class="kt">int</span> <span class="n">n</span><span class="p">)</span> <span class="p">{</span> |
| <span class="k">auto</span> <span class="n">id</span> <span class="o">=</span> <span class="n">std</span><span class="o">::</span><span class="n">this_thread</span><span class="o">::</span><span class="n">get_id</span><span class="p">();</span> |
| <span class="k">for</span> <span class="p">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">n</span><span class="p">;</span> <span class="o">++</span><span class="n">i</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">ostringstream</span> <span class="n">ss</span><span class="p">;</span> |
| <span class="n">ss</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">this_thread</span><span class="o">::</span><span class="n">get_id</span><span class="p">()</span> <span class="o"><<</span> <span class="s">"-"</span> <span class="o"><<</span> <span class="n">i</span><span class="p">;</span> |
| <span class="n">s</span><span class="p">.</span><span class="n">send</span><span class="p">(</span><span class="n">proton</span><span class="o">::</span><span class="n">message</span><span class="p">(</span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()));</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">id</span> <span class="o"><<</span> <span class="s">" sent </span><span class="se">\"</span><span class="s">"</span> <span class="o"><<</span> <span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span> <span class="o"><<</span> <span class="sc">'"'</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">id</span> <span class="o"><<</span> <span class="s">" sent "</span> <span class="o"><<</span> <span class="n">n</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="p">}</span> |
| |
| <span class="c1">// Receive messages till atomic remaining count is 0.</span> |
| <span class="c1">// remaining is shared among all receiving threads</span> |
| <span class="kt">void</span> <span class="nf">receive_thread</span><span class="p">(</span><span class="n">receiver</span><span class="o">&</span> <span class="n">r</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="n">atomic_int</span><span class="o">&</span> <span class="n">remaining</span><span class="p">)</span> <span class="p">{</span> |
| <span class="k">try</span> <span class="p">{</span> |
| <span class="k">auto</span> <span class="n">id</span> <span class="o">=</span> <span class="n">std</span><span class="o">::</span><span class="n">this_thread</span><span class="o">::</span><span class="n">get_id</span><span class="p">();</span> |
| <span class="kt">int</span> <span class="n">n</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> |
| <span class="c1">// atomically check and decrement remaining *before* receiving.</span> |
| <span class="c1">// If it is 0 or less then return, as there are no more</span> |
| <span class="c1">// messages to receive so calling r.receive() would block forever.</span> |
| <span class="k">while</span> <span class="p">(</span><span class="n">remaining</span><span class="o">--</span> <span class="o">></span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span> |
| <span class="k">auto</span> <span class="n">m</span> <span class="o">=</span> <span class="n">r</span><span class="p">.</span><span class="n">receive</span><span class="p">();</span> |
| <span class="o">++</span><span class="n">n</span><span class="p">;</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">id</span> <span class="o"><<</span> <span class="s">" received </span><span class="se">\"</span><span class="s">"</span> <span class="o"><<</span> <span class="n">m</span><span class="p">.</span><span class="n">body</span><span class="p">()</span> <span class="o"><<</span> <span class="sc">'"'</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="n">OUT</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">id</span> <span class="o"><<</span> <span class="s">" received "</span> <span class="o"><<</span> <span class="n">n</span> <span class="o"><<</span> <span class="s">" messages"</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">);</span> |
| <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="k">const</span> <span class="n">closed</span><span class="o">&</span><span class="p">)</span> <span class="p">{}</span> |
| <span class="p">}</span> |
| |
| <span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="k">const</span> <span class="kt">char</span> <span class="o">**</span><span class="n">argv</span><span class="p">)</span> <span class="p">{</span> |
| <span class="k">try</span> <span class="p">{</span> |
| <span class="k">if</span> <span class="p">(</span><span class="n">argc</span> <span class="o">!=</span> <span class="mi">5</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> |
| <span class="s">"Usage: "</span> <span class="o"><<</span> <span class="n">argv</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o"><<</span> <span class="s">" CONNECTION-URL AMQP-ADDRESS MESSAGE-COUNT THREAD-COUNT</span><span class="se">\n</span><span class="s">"</span> |
| <span class="s">"CONNECTION-URL: connection address, e.g.'amqp://127.0.0.1'</span><span class="se">\n</span><span class="s">"</span> |
| <span class="s">"AMQP-ADDRESS: AMQP node address, e.g. 'examples'</span><span class="se">\n</span><span class="s">"</span> |
| <span class="s">"MESSAGE-COUNT: number of messages to send</span><span class="se">\n</span><span class="s">"</span> |
| <span class="s">"THREAD-COUNT: number of sender/receiver thread pairs</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span> |
| <span class="k">return</span> <span class="mi">1</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">const</span> <span class="kt">char</span> <span class="o">*</span><span class="n">url</span> <span class="o">=</span> <span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">];</span> |
| <span class="k">const</span> <span class="kt">char</span> <span class="o">*</span><span class="n">address</span> <span class="o">=</span> <span class="n">argv</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span> |
| <span class="kt">int</span> <span class="n">n_messages</span> <span class="o">=</span> <span class="n">atoi</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">3</span><span class="p">]);</span> |
| <span class="kt">int</span> <span class="n">n_threads</span> <span class="o">=</span> <span class="n">atoi</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">4</span><span class="p">]);</span> |
| <span class="kt">int</span> <span class="n">count</span> <span class="o">=</span> <span class="n">n_messages</span> <span class="o">*</span> <span class="n">n_threads</span><span class="p">;</span> |
| |
| <span class="c1">// Total messages to be received, multiple receiver threads will decrement this.</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">atomic_int</span> <span class="n">remaining</span><span class="p">;</span> |
| <span class="n">remaining</span><span class="p">.</span><span class="n">store</span><span class="p">(</span><span class="n">count</span><span class="p">);</span> |
| |
| <span class="c1">// Run the proton container</span> |
| <span class="n">proton</span><span class="o">::</span><span class="n">container</span> <span class="n">container</span><span class="p">;</span> |
| <span class="k">auto</span> <span class="n">container_thread</span> <span class="o">=</span> <span class="n">std</span><span class="o">::</span><span class="kr">thread</span><span class="p">([</span><span class="o">&</span><span class="p">]()</span> <span class="p">{</span> <span class="n">container</span><span class="p">.</span><span class="n">run</span><span class="p">();</span> <span class="p">});</span> |
| |
| <span class="c1">// A single sender and receiver to be shared by all the threads</span> |
| <span class="n">sender</span> <span class="n">send</span><span class="p">(</span><span class="n">container</span><span class="p">,</span> <span class="n">url</span><span class="p">,</span> <span class="n">address</span><span class="p">);</span> |
| <span class="n">receiver</span> <span class="n">recv</span><span class="p">(</span><span class="n">container</span><span class="p">,</span> <span class="n">url</span><span class="p">,</span> <span class="n">address</span><span class="p">);</span> |
| |
| <span class="c1">// Start receiver threads, then sender threads.</span> |
| <span class="c1">// Starting receivers first gives all receivers a chance to compete for messages.</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="kr">thread</span><span class="o">></span> <span class="n">threads</span><span class="p">;</span> |
| <span class="n">threads</span><span class="p">.</span><span class="n">reserve</span><span class="p">(</span><span class="n">n_threads</span><span class="o">*</span><span class="mi">2</span><span class="p">);</span> <span class="c1">// Avoid re-allocation once threads are started</span> |
| <span class="k">for</span> <span class="p">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">n_threads</span><span class="p">;</span> <span class="o">++</span><span class="n">i</span><span class="p">)</span> |
| <span class="n">threads</span><span class="p">.</span><span class="n">push_back</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="kr">thread</span><span class="p">([</span><span class="o">&</span><span class="p">]()</span> <span class="p">{</span> <span class="n">receive_thread</span><span class="p">(</span><span class="n">recv</span><span class="p">,</span> <span class="n">remaining</span><span class="p">);</span> <span class="p">}));</span> |
| <span class="k">for</span> <span class="p">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">n_threads</span><span class="p">;</span> <span class="o">++</span><span class="n">i</span><span class="p">)</span> |
| <span class="n">threads</span><span class="p">.</span><span class="n">push_back</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="kr">thread</span><span class="p">([</span><span class="o">&</span><span class="p">]()</span> <span class="p">{</span> <span class="n">send_thread</span><span class="p">(</span><span class="n">send</span><span class="p">,</span> <span class="n">n_messages</span><span class="p">);</span> <span class="p">}));</span> |
| |
| <span class="c1">// Wait for threads to finish</span> |
| <span class="k">for</span> <span class="p">(</span><span class="k">auto</span><span class="o">&</span> <span class="nl">t</span> <span class="p">:</span> <span class="n">threads</span><span class="p">)</span> <span class="n">t</span><span class="p">.</span><span class="n">join</span><span class="p">();</span> |
| <span class="n">send</span><span class="p">.</span><span class="n">close</span><span class="p">();</span> |
| <span class="n">recv</span><span class="p">.</span><span class="n">close</span><span class="p">();</span> |
| <span class="n">container_thread</span><span class="p">.</span><span class="n">join</span><span class="p">();</span> |
| <span class="k">if</span> <span class="p">(</span><span class="n">remaining</span> <span class="o">></span> <span class="mi">0</span><span class="p">)</span> |
| <span class="k">throw</span> <span class="n">std</span><span class="o">::</span><span class="n">runtime_error</span><span class="p">(</span><span class="s">"not all messages were received"</span><span class="p">);</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">count</span> <span class="o"><<</span> <span class="s">" messages sent and received"</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> |
| |
| <span class="k">return</span> <span class="mi">0</span><span class="p">;</span> |
| <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">exception</span><span class="o">&</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> <span class="n">e</span><span class="p">.</span><span class="n">what</span><span class="p">()</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> |
| <span class="p">}</span> |
| <span class="k">return</span> <span class="mi">1</span><span class="p">;</span> |
| <span class="p">}</span> |
| </pre></div> |
| |
| <p><a href="multithreaded_client_flow_control.cpp">Download this file</a></p> |
