separate redis from app.js

inc/redis.js

@@ -0,0 +1,51 @@
+const config = require('../config');
+const { promisify } = require('util');
+const r = require('redis');
+
+const redisOptions = {
+  host: '127.0.0.1',
+  port: 6379,
+};
+
+if (config.redis_db) {
+  redisOptions.db = config.redis_db;
+}
+
+if (config.redis_host) {
+  redisOptions.host = config.redis_host;
+}
+
+if (config.redis_port && config.redis_port > 0) {
+  redisOptions.port = config.redis_port;
+}
+
+if (config.redis_password) {
+  redisOptions.password = config.redis_password;
+}
+
+// Stub Redis if disabled
+const stub = {
+  get: (_, callback) => callback(null, null),
+  setex: (_, _1, _2, callback) => callback(null),
+  on: () => {},
+};
+
+const redisDisabled = !config.redis_enabled;
+
+const redis = redisDisabled ? stub : r.createClient(redisOptions);
+
+const redisAsync = {
+  get: promisify(redis.get).bind(redis),
+  setex: promisify(redis.setex).bind(redis),
+};
+
+redis.on('error', (error) => {
+  if (error) {
+    console.error(`Redis error: ${error}`);
+  }
+});
+
+module.exports = {
+  redis,
+  redisAsync,
+};