Add enqueue event to protocol and connection

fixes #381

Author: dougwilson

Changes.md

@@ -4,6 +4,10 @@ This file is a manually maintained list of changes for each release. Feel free
 to add your changes here when sending pull requests. Also send corrections if
 you spot any mistakes.
 
+## HEAD
+
+* Add `enqueue` event to protocol and connection #381
+
 ## v2.4.1 (2014-07-17)
 
 * Fix `pool.query` not invoking callback on connection error #872

lib/Connection.js

@@ -94,6 +94,7 @@ Connection.prototype.connect = function connect(options, callback) {
     this._protocol.on('unhandledError', this._handleProtocolError.bind(this));
     this._protocol.on('drain', this._handleProtocolDrain.bind(this));
     this._protocol.on('end', this._handleProtocolEnd.bind(this));
+    this._protocol.on('enqueue', this._handleProtocolEnqueue.bind(this));
 
     if (this.config.connectTimeout) {
       var handleConnectTimeout = this._handleConnectTimeout.bind(this);
@@ -363,6 +364,10 @@ Connection.prototype._handleProtocolEnd = function(err) {
   this.emit('end', err);
 };
 
+Connection.prototype._handleProtocolEnqueue = function _handleProtocolEnqueue(sequence) {
+  this.emit('enqueue', sequence);
+};
+
 Connection.prototype._implyConnect = function() {
   if (!this._connectCalled) {
     this.connect();

lib/protocol/Protocol.js

@@ -136,6 +136,7 @@ Protocol.prototype._enqueue = function(sequence) {
   }
 
   this._queue.push(sequence);
+  this.emit('enqueue', sequence);
 
   var self = this;
   sequence

test/unit/connection/test-enqueue-event.js

@@ -0,0 +1,24 @@
+var assert     = require('assert');
+var common     = require('../../common');
+var connection = common.createConnection({port: common.fakeServerPort});
+
+var server = common.createFakeServer();
+
+server.listen(common.fakeServerPort, function (err) {
+  assert.ifError(err);
+
+  var count = 0;
+  connection.on('enqueue', function () {
+    count++;
+  });
+
+  connection.on('drain', function () {
+    assert.equal(count, 3);
+    connection.destroy();
+    server.destroy();
+  });
+
+  connection.query('SELECT 1', assert.ifError);
+  connection.ping(assert.ifError);
+});
+