run cron at full hours

closes #20

src/utils/cron.js

@@ -1,37 +1,47 @@
 /*
  * Cron job of argumentless functions that will get run in a specific interval,
- * per default just one will get created which runs daily,
- * hook it up to some timer function that causes the least load
- * @flow
+ * at full hours
  */
 import { HOUR } from '../core/constants';
 
 import logger from '../core/logger';
 
 class Cron {
-  lastRun: number;
-  interval: number;
-  functions: Array;
+  // timestamp of last run
+  lastRun;
+  // interval in hours
+  interval;
+  // array with functions to run
+  functions;
+  // timeout return
   timeout;
 
   // interval = how many hours between runs
   // lastRun = when this cron job was last run
-  constructor(interval: number, lastRun: number = 0) {
+  constructor(interval, lastRun = 0) {
     this.checkForExecution = this.checkForExecution.bind(this);
     this.interval = interval;
     this.lastRun = lastRun;
     this.functions = [];
 
-    this.timeout = setInterval(this.checkForExecution, HOUR);
+    const ct = new Date();
+    const msToNextFullHour = 3600000
+      - (ct.getUTCMinutes() * 60 + ct.getUTCSeconds()) * 1000;
+    this.timeout = setTimeout(this.checkForExecution, msToNextFullHour);
   }
 
   checkForExecution() {
     const curTime = Date.now();
-    if (curTime > this.lastRun + this.interval * HOUR) {
+    this.timeout = setTimeout(this.checkForExecution, HOUR);
+    if (curTime + 10000 > this.lastRun + this.interval * HOUR) {
       logger.info(`Run cron events for interval: ${this.interval}h`);
       this.lastRun = curTime;
       this.functions.forEach(async (item) => {
-        item();
+        try {
+          item();
+        } catch (err) {
+          logger.error(`Error on cron job: ${err.message}`);
+        }
       });
     }
   }
@@ -45,7 +55,9 @@ class Cron {
 function initializeDailyCron() {
   const now = new Date();
   // make it first run at midnight
-  const lastRun = now.getTime() - now.getHours() * HOUR;
+  const lastRun = now.getTime()
+    - now.getUTCHours() * HOUR
+    - (now.getUTCMinutes() * 60 - now.getUTCSeconds()) * 1000;
   const cron = new Cron(24, lastRun);
   return cron;
 }