adding logstash UDP appender

lib/appenders/logstashUDP.js

@@ -0,0 +1,50 @@
+"use strict";
+var layouts = require('../layouts')
+, dgram = require('dgram')
+, util = require('util');
+
+function logstashUDP (config, layout) {
+  var udp = dgram.createSocket('udp4');
+  var type = config.logType ? config.logType : config.category;
+  layout = layout || layouts.colouredLayout;
+  if(!config.fields) {
+    config.fields = {};
+  }
+  return function(loggingEvent) {
+    var logMessage = layout(loggingEvent);
+    var fields = {};
+    for(var i in config.fields) {
+      fields[i] = config.fields[i];
+    }
+    fields['level'] = loggingEvent.level.levelStr;
+    var logObject = {
+      '@timestamp': (new Date(loggingEvent.startTime)).toISOString(),
+      type: type,
+      message: logMessage,
+      fields: fields
+    };
+    sendLog(udp, config.host, config.port, logObject);
+  };
+}
+
+function sendLog(udp, host, port, logObject) {
+  var buffer = new Buffer(JSON.stringify(logObject));
+  udp.send(buffer, 0, buffer.length, port, host, function(err, bytes) {
+    if(err) {
+      console.error(
+        "log4js.logstashUDP - %s:%p Error: %s", host, port, util.inspect(err)
+      );
+    }
+  });
+}
+
+function configure(config) {
+  var layout;
+  if (config.layout) {
+    layout = layouts.layout(config.layout.type, config.layout);
+  }
+  return logstashUDP(config, layout);
+}
+
+exports.appender = logstashUDP;
+exports.configure = configure;