added shutdownTimeout option

lib/appenders/smtp.js

@@ -2,7 +2,8 @@
 var layouts = require("../layouts")
 , mailer = require("nodemailer")
 , os = require('os')
-, unsentCount = 0;
+, unsentCount = 0
+, shutdownTimeout;
 
 /**
 * SMTP Appender. Sends logging events using SMTP protocol. 
@@ -12,6 +13,7 @@ var layouts = require("../layouts")
 * @param config appender configuration data
 *    config.sendInterval time between log emails (in seconds), if 0
 *    then every event sends an email
+*    config.shutdownTimeout time to give up remaining emails (in seconds; defaults to 5).
 * @param layout a function that takes a logevent and returns a string (defaults to basicLayout).
 */
 function smtpAppender(config, layout) {
@@ -22,6 +24,8 @@ function smtpAppender(config, layout) {
 	var logEventBuffer = [];
 	var sendTimer;
 	
+	shutdownTimeout = ('shutdownTimeout' in config ? config.shutdownTimeout : 5) * 1000;
+	
 	function sendBuffer() {
     if (logEventBuffer.length > 0) {
 		
@@ -87,8 +91,11 @@ function configure(config) {
 }
 
 function shutdown(cb) {
-	async.until(function() {
-		return unsentCount === 0;
+	if (shutdownTimeout > 0) {
+		setTimeout(function() { unsentCount = 0; }, shutdownTimeout);
+	}
+	async.whilst(function() {
+		return unsentCount > 0;
 	}, function(done) {
 		setTimeout(done, 100);
 	}, cb);