add shutdown command for the logstore

lib/log.js

@@ -52,6 +52,9 @@ var createLogType = function (ctx, type) {
         return noop;
     }
     return function (tag, info) {
+        if (ctx.shutdown) {
+            throw new Error("Logger has been shut down!");
+        }
         var time = new Date().toISOString();
         var content;
         try {
@@ -98,7 +101,13 @@ Logger.create = function (config, cb) {
         filePath: config.logPath,
     }, function (store) {
         ctx.store = store;
-        cb(Object.freeze(createMethods(ctx)));
+        var logger = createMethods(ctx);
+        logger.shutdown = function () {
+            delete ctx.store;
+            ctx.shutdown = true;
+            store.shutdown();
+        };
+        cb(Object.freeze(logger));
     });
 };