Use MySQL Pool and add error handling for offline DB

Author: keitharm

app.js

@@ -15,6 +15,7 @@ const _            = require('lodash');
 const logger       = require('./utils').logger;
 const syslog       = require('./utils').syslog;
 const settings     = require('./utils').settings;
+const dbStatus     = require('./utils').dbStatus;
 
 const User = require('./models/User');
 const Tier = require('./models/Tier');
@@ -97,6 +98,10 @@ app.use(bodyParser.urlencoded({ limit: '5mb', extended: false }));
 app.use(express.static(path.join(__dirname, 'public')));
 
 app.use('*', (req, res, next) => {
+  if (!dbStatus()) {
+    return res.render('epicfail', {basehref: settings.general.basehref, messages: null, title: 'Uh oh, something bad has happened'});
+  }
+
   // Skip if user is accessing api
   if (req.params[0].slice(0, 5) === '/api/') next();
   else {

models/db.js

@@ -1,14 +1,15 @@
 const mysql    = require('mysql');
 const settings = require('../utils').settings;
 const logger   = require('../utils').logger;
+const dbStatus = require('../utils').dbStatus;
 
 let db = settings.db.prod;
 
 if (process.env.spec === "true") {
   db = settings.db.spec
 }
 
-var connection = mysql.createPool({
+var pool = mysql.createPool({
   connectionLimit: 10,
   host:       db.host,
   socketPath: db.socketPath,
@@ -20,15 +21,68 @@ var connection = mysql.createPool({
 
 module.exports.init = function(cb) {
 
-  connection.on('connection', connection => {
+  pool.on('connection', connection => {
     logger('[db]: connected as id ' + connection.threadId);
     cb();
   });
 
+  pool.getConnection((err, connection) => {
+    if (err) {
+      return dbStatus(false);
+    }
+      connection.query('SELECT 1', [], () => {
+        dbStatus(true);
+        connection.release();
+      });
+    });
+
   // Keep connection alive
   setInterval(() => {
-      connection.query('SELECT 1');
+    pool.getConnection((err, connection) => {
+      if (err) {
+        return dbStatus(false);
+      }
+      connection.query('SELECT 1', [], () => {
+        dbStatus(true);
+        connection.release();
+      });
+    });
   }, db.keepAliveInterval);
 };
 
-module.exports.connection = connection;
+module.exports.connection = {
+  query: function () {
+    let queryArgs = Array.prototype.slice.call(arguments),
+        events = [],
+        eventNameIndex = {};
+
+    pool.getConnection((err, conn) => {
+        if (err) {
+            if (eventNameIndex.error) {
+                eventNameIndex.error();
+            }
+        }
+        if (conn) {
+            let q = conn.query.apply(conn, queryArgs);
+            q.on('end', () => {
+                conn.release();
+            });
+
+            events.forEach(args => {
+                q.on.apply(q, args);
+            });
+        }
+    });
+
+    return {
+        on: function (eventName, callback) {
+            events.push(Array.prototype.slice.call(arguments));
+            eventNameIndex[eventName] = callback;
+            return this;
+        }
+    };
+  },
+  escape: val => pool.escape(val)
+};
+
+//module.exports.connection = connection;

server.js

@@ -22,7 +22,7 @@ const db = require('./models/db').init(() => {
   });
 
   server.listen(app.get('port'));
-  server.on('error', error => {
+  server.once('error', error => {
     let bind = app.get('port');
     switch (error.code) {
       case 'EACCES':
@@ -38,7 +38,7 @@ const db = require('./models/db').init(() => {
     }
   });
 
-  server.on('listening', () => {
+  server.once('listening', () => {
     let addr = server.address();
     let bind = typeof addr === 'string'
       ? 'pipe ' + addr

utils.js

@@ -8,6 +8,8 @@ const stripe   = require("stripe")(settings.stripe.secretKey);
 redis.config('SET', 'maxmemory', settings.general.redisMaxMemory);
 redis.on('error', err => module.exports.logger(err) && module.exports.syslog(err));
 
+let dbOnline = true;
+
 module.exports = {
   pad(n, width, z) {
     z = z || '0';
@@ -79,6 +81,13 @@ module.exports = {
   missingProps(obj, expected) {
     return !expected.every(prop => prop in obj && obj[prop] !== undefined);
   },
+  dbStatus(status) {
+    if (status === undefined) {
+      return dbOnline;
+    } else {
+      dbOnline = status;
+    }
+  },
   redis,
   stripe,
   settings

views/pages/epicfail.ejs

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <% include ../snippets/header %>
+  <link rel="stylesheet" href="css/demoEditor.css">
+</head>
+<body>
+  <div class="main">
+    <section class="hero">
+      <h3>Uh oh, something has gone wrong.</h3>
+      <h5 id="subtitle">Please try your request again later. If the problem still persists, please send us a tweet <a href="http://twitter.com/randomapi" class="green">@RandomAPI</a>. Thanks!</h5>
+    </section>
+  </div>
+  <% include ../snippets/footer %>
+</body>
+</html>