Another OpenWhisk Cron Example - the Blog Nag

Another OpenWhisk Cron Example - the Blog Nag

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Last week I blogged about my first experience working with OpenWhisk triggers and rules, specifically the Cron trigger which lets you execute actions according to a schedule. Today I'm sharing another example, which, while not as complex as the 911 scraper, I thought was kind of fun.

As a blogger, I try to keep to a certain amount of posts per month. While I a absolutely care more about quality than quantity, I still try to maintain a certain amount of content per month. I thought it would be fun to create an OpenWhisk action that would nag me if I hadn't blogged in a few days. This turned out to be rather simple:

  • First, I get the RSS feed.
  • Then I parse the XML. There's packages to read RSS, but there's also xml2js which just does a basic conversion.
  • I can then check the date of the most recent article and compare it to now.
  • If it's been too long, nag!

Let's start with the action:

const request = require('request');
const parseString = require('xml2js').parseString;

//number of days you have till i bug you
const NAG_DAY = 2;

//SendGrid API Key
const SG_KEY = 'SG.whywontanyonecommentonthestuffiputhere';
const helper = require('sendgrid').mail;

function doNag(last) {

	let from_email = new helper.Email('');
	let to_email = new helper.Email('');
	let subject = 'You Need to Blog!';

	let content = `
You have not blogged in the past ${NAG_DAY} days!
Your last post was on ${last}.
	let mailContent = new helper.Content('text/plain', content);
	let mail = new helper.Mail(from_email, subject, to_email, mailContent);
	let sg = require('sendgrid')(SG_KEY);

	var request = sg.emptyRequest({
		method: 'POST',
		path: '/v3/mail/send',
		body: mail.toJSON()
	sg.API(request, function(error, response) {
		if(error) {
		} else {
			//right now we do nothing really

function main() {

	let rssurl = '';

	return new Promise((resolve, reject) => {

		request.get(rssurl, function(error, response, body) {
			if(error) return reject(error);

			parseString(body, function(err, result) {
				if(err) return reject(err);

				//Latest post:
				let latest =[0].item[0];
				//now lets try to parse the date
				let latestDate = new Date(latest.pubDate[0]).getTime();
				//alright then - so compare Now to latestDate
				let now =;
				//difference is how much time (duh)
				let diff = now - latestDate;
				if(diff > (NAG_DAY * 24 * 60 * 60 * 1000)) {
					console.log('got to nag!');
				} else {



exports.main = main;

Start with the main function which is OpenWhisk's entry point to the function. I use the request library to open up my RSS feed and then parseString from the xml2js library. I can then get the most recent blog entry (which is the first entry in a RSS feed) and make a date object with it.

Once I have that - then it's math. I set the constant NAG_DAY to 2, which is a bit too low if you ask me, but I had blogged on Friday so I needed a value that would trigger the alert. (For folks curious, I try to blog once every 3 days.) If we need to nag, we then simply call doNag.

The doNag function just writes an email using the Sendgrid API and fires it out. And that's it.

So then I had to make this "live" - which beforehand would have meant provisioning a server and all that, but with the wonders of Serverless (yes, I'm half-joking here ;) I just did the following:

  • Sent the action up to OpenWhisk with the CLI (wsk action create --kind nodejs:6 rssnag
  • Made the trigger (wsk trigger create checkBlog --feed /whisk.system/alarms/alarm --param cron "* * 1 * *"). That Cron value is for once a day, and yes I had to use again.
  • Made the rule (wsk rule create blogNagRule checkBlog rssnag)

And that's it. To test I used the OpenWhisk UI on IBM Bluemix and manually triggered it. And the result....

Email ftw

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About Raymond Camden

Raymond is a senior developer evangelist for Adobe. He focuses on document services, JavaScript, and enterprise cat demos. If you like this article, please consider visiting my Amazon Wishlist or donating via PayPal to show your support. You can even buy me a coffee!

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