Provided a tutorial for RabbitMq priority queue implementation

examples/tutorials/README.md

@@ -80,6 +80,14 @@ and routing replies back to clients.
  * [rpc_server.js](rpc_server.js)
  * [rpc_client.js](rpc_client.js)
 
+## [Tutorial seven: Priority Queue][tute-seven]
+
+RabbitMQ has priority queue implementation in the core as of version 3.5.0.
+Using RabbitMQ as a priority queue, showing how to set maximum priority value supported by the queue and setting priority of each message pushed to the queue. In case of messages having equal value of priority, they are consumed in FIFO order.
+
+ * [send_priority_queue.js](callback_api/send_priority_queue.js)
+ * [receive_priority_queue.js](callback_api/receive_priority_queue.js)
+
 I depart slightly from the original tutorial code, which I think has
 some needless object-orientation (in the Python code; you don't get a
 choice about needless object-orientation in Java).
@@ -91,3 +99,4 @@ choice about needless object-orientation in Java).
 [tute-four]: http://www.rabbitmq.com/tutorials/tutorial-four-python.html
 [tute-five]: http://www.rabbitmq.com/tutorials/tutorial-five-python.html
 [tute-six]: http://www.rabbitmq.com/tutorials/tutorial-six-python.html
+[tute-seven]: https://www.rabbitmq.com/priority.html

examples/tutorials/callback_api/receive_priority_queue.js

@@ -0,0 +1,30 @@
+#!/usr/bin/env node
+
+var amqp = require('amqplib/callback_api');
+
+function bail(err, conn) {
+  console.error(err);
+  if (conn) conn.close(function() { process.exit(1); });
+}
+
+function on_connect(err, conn) {
+  if (err !== null) return bail(err);
+  process.once('SIGINT', function() { conn.close(); });
+
+  var q = 'hello';
+
+  function on_channel_open(err, ch) {
+    ch.assertQueue(q, {durable: false, maxPriority: 10}, function(err, ok) {
+      if (err !== null) return bail(err, conn);
+      ch.consume(q, function(msg) { // message callback
+        console.log(" [x] Received '%s'", msg.content.toString());
+      }, {noAck: true}, function(_consumeOk) { // consume callback
+        console.log(' [*] Waiting for messages. To exit press CTRL+C');
+      });
+    });
+  }
+
+  conn.createChannel(on_channel_open);
+}
+
+amqp.connect(on_connect);

examples/tutorials/callback_api/send_priority_queue.js

@@ -0,0 +1,36 @@
+#!/usr/bin/env node
+
+var amqp = require('amqplib/callback_api');
+
+function bail(err, conn) {
+  console.error(err);
+  if (conn) conn.close(function() { process.exit(1); });
+}
+
+function on_connect(err, conn) {
+  if (err !== null) return bail(err);
+
+  var q = 'hello';
+  var message = '';
+  var priorityValue = 0;
+
+  function on_channel_open(err, ch) {
+    if (err !== null) return bail(err, conn);
+    ch.assertQueue(q, {durable: false, maxPriority: 10}, function(err, ok) {
+      if (err !== null) return bail(err, conn);
+
+      for(var index=1; index<=50; index++) {
+        priorityValue = Math.floor((Math.random() * 10));
+        // index refers to message number. Lower is the index value, earlier is the message pushed into the queue.
+        message = 'Message index = ' + index + ' and Priority Value = ' + priorityValue;
+        ch.sendToQueue(q, new Buffer(message), {priority: priorityValue});
+        console.log(" [x] Sent '%s'", message);
+      }
+      ch.close(function() { conn.close(); });
+    });
+  }
+
+  conn.createChannel(on_channel_open);
+}
+
+amqp.connect(on_connect);