Default to ephemeral sockets

The use of a single, shared socket that's never closed prevents node processes
from completing normally.

This change allows an optional shared socket to be passed into the constructor.
If present, node-statsd will use that (and will assume that the provider will
close it when appropriate).  Otherwise, node-statsd will create new sockets for
each connection (the old, less efficient behavior).

lib/statsd.js

@@ -1,11 +1,14 @@
 var sys = require('sys')
-  , socket = require('dgram').createSocket('udp4')
+  , dgram = require('dgram')
   , mersenne = require('mersenne')
   , mt = new mersenne.MersenneTwister19937();
 
-Client = function (host, port) {
+Client = function (host, port, socket) {
     this.host = host;
     this.port = port;
+
+    // optional shared socket
+    this.socket = socket;
 }
 
 Client.prototype.timing = function (stat, time, sample_rate) {
@@ -40,6 +43,28 @@ Client.prototype.update_stats = function (stats, delta, sampleRate) {
     self.send(data, sampleRate);
 }
 
+Client.prototype.send_data = function (buffer) {
+    var self = this;
+    var socket;
+
+    if (this.socket === undefined) {
+        socket = dgram.createSocket('udp4');
+    } else {
+        socket = this.socket;
+    }
+
+    socket.send(buffer, 0, buffer.length, this.port, this.host, function (err, bytes) {
+        if (err) {
+            console.log("Error while sending data:", err.msg);
+        }
+
+        if (self.socket === undefined) {
+            // close ephemeral sockets while keeping shared ones open
+            socket.close();
+        }
+    });
+}
+
 Client.prototype.send = function (data, sample_rate) {
     var self = this;
     if (!sample_rate) {
@@ -60,14 +85,7 @@ Client.prototype.send = function (data, sample_rate) {
     }
     for (stat in sampled_data) {
         send_data = stat+":"+sampled_data[stat];
-        send_data = new Buffer(send_data);
-        socket.send(send_data, 0, send_data.length, self.port, self.host,
-                    function (err, bytes) {
-                        if (err) {
-                            console.log(err.msg);
-                        }
-                    }
-                   );
+        this.send_data(new Buffer(send_data));
     }
 };