Fix #19 by adding a lock to level db connector

storage/lvl.js

@@ -17,14 +17,26 @@ var getIndex = function(db, cName, cb) {
 
 var insert = function (db, channelName, content, cb) {
     var index;
+    var doIt = function () {
+        db.locked = true;
         nThen(function (waitFor) {
             getIndex(db, channelName, waitFor(function (i) { index = i+1; }));
         }).nThen(function (waitFor) {
             db.put(channelName+'=>'+index, content, waitFor(function (e) { if (e) { throw e; } }));
         }).nThen(function (waitFor) {
             db.put(channelName+'=>index', ''+index, waitFor(function (e) { if (e) { throw e; } }));
+        }).nThen(function (waitFor) {
+            db.locked = false;
+            if (!db.queue.length) { return; }
+            db.queue.shift()();
         }).nThen(cb);
     };
+    if (db.locked) {
+        db.queue.push(doIt);
+    } else {
+        doIt();
+    }
+};
 
 var getMessages = function (db, channelName, msgHandler) {
     var index;
@@ -44,6 +56,8 @@ var getMessages = function (db, channelName, msgHandler) {
 
 module.exports.create = function (conf, cb) {
     var db = Level(conf.levelPath || './test.level.db');
+    db.locked = false;
+    db.queue = [];
     cb({
         message: function (channelName, content, cb) {
             insert(db, channelName, content, cb);