Allow shutting down of appenders without disabling future log writes

lib/appenders/file.js

@@ -80,7 +80,9 @@ function configure(config, options) {
 }
 
 function shutdown(cb) {
-  async.each(openFiles, function(file, done) {
+  var filesToClose = openFiles;
+  openFiles = [];
+  async.each(filesToClose, function(file, done) {
     if (!file.write(eol, "utf-8")) {
       file.once('drain', function() {
         file.end(done);

lib/log4js.js

@@ -176,6 +176,11 @@ function clearAppenders () {
   }
 }
 
+function clearAndShutdownAppenders(cb) {
+  clearAppenders();
+  shutdownAppenders(cb);
+}
+
 function configureAppenders(appenderList, options) {
   clearAppenders();
   if (appenderList) {
@@ -380,7 +385,10 @@ function shutdown(cb) {
   // First, disable all writing to appenders. This prevents appenders from
   // not being able to be drained because of run-away log writes.
   loggerModule.disableAllLogWrites();
+  shutdownAppenders(cb);
+}
 
+function shutdownAppenders(cb) {
   // Next, get all the shutdown functions for appenders as an array.
   var shutdownFunctions = Object.keys(appenderShutdowns).reduce(
     function(accum, category) {
@@ -406,6 +414,7 @@ module.exports = {
   addAppender: addAppender,
   loadAppender: loadAppender,
   clearAppenders: clearAppenders,
+  clearAndShutdownAppenders: clearAndShutdownAppenders,
   configure: configure,
   shutdown: shutdown,