Add new optional parameter to have all sockets send KeepAlive packets

Readme.md

@@ -235,6 +235,7 @@ issue [#501](https://github.com/mysqljs/mysql/issues/501). (Default: `false`)
   also possible to blacklist default ones. For more information, check
   [Connection Flags](#connection-flags).
 * `ssl`: object with ssl parameters or a string containing name of ssl profile. See [SSL options](#ssl-options).
+* `keepAliveDelay`: Delay in milliseconds after which the connection socket will send a keepalive packet. See [Net.socket.setKeepAlive](https://nodejs.org/api/net.html#net_socket_setkeepalive_enable_initialdelay).
 
 
 In addition to passing these options as an object, you can also use a url

lib/Connection.js

@@ -431,6 +431,9 @@ Connection.prototype._handleProtocolDrain = function() {
 
 Connection.prototype._handleProtocolConnect = function() {
   this.state = 'connected';
+  if (this.config.keepAliveDelay) {
+    this._socket.setKeepAlive(true, this.config.keepAliveDelay);
+  }
   this.emit('connect');
 };
 

lib/ConnectionConfig.js

@@ -37,6 +37,7 @@ function ConnectionConfig(options) {
   this.typeCast           = (options.typeCast === undefined)
     ? true
     : options.typeCast;
+  this.keepAliveDelay     = options.keepAliveDelay || 0;
 
   if (this.timezone[0] === ' ') {
     // "+" is a url encoded char for space so it

test/unit/connection/test-connect-keepalive.js

@@ -0,0 +1,16 @@
+var assert     = require('assert');
+var common     = require('../../common');
+var connection = common.createConnection({keepAliveDelay: 60000, port: common.fakeServerPort});
+
+var server = common.createFakeServer();
+
+server.listen(common.fakeServerPort, function (err) {
+  assert.ifError(err);
+
+  connection.on('connect', function () {
+    connection.destroy();
+    server.destroy();
+  });
+
+  connection.connect(assert.ifError);
+});

test/unit/test-ConnectionConfig.js

@@ -64,6 +64,17 @@ test('ConnectionConfig#Constructor', {
   'blacklists unsupported client flags': function() {
     var config = new ConnectionConfig({ flags: '+CONNECT_ATTRS' });
     assert.equal(config.clientFlags & common.ClientConstants.CLIENT_CONNECT_ATTRS, 0);
+  },
+
+  'Socket keepAlive defaults to 0 (default)': function() {
+    var config = new ConnectionConfig({});
+    assert.equal(config.keepAliveDelay, 0);
+  },
+
+  'Socket keepAlive is set in config': function()
+  {
+    var config = new ConnectionConfig({ keepAliveDelay: 60000 });
+    assert.equal(config.keepAliveDelay, 60000);
   }
 });