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Build a Serverless Slack Bot With Webtasks

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Build a Serverless Slack Bot With Webtasks

Who hasn't wanted to build a bot? But making sure your server is set up and working is a pain. See how you can use webtasks instead of hardware and get your bot chatting.

· Cloud Zone ·
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Whenever you get a cool idea to create an app, the mere thought of preparing and maintaining a server always gets you down. Not to mention all the security considerations you have to think through. The advent of PaaS services like Heroku solved this to some extent. Now that serverless technologies have come into the mainstream, bringing your ideas into reality is easier than ever.

Serverless platforms allow you to focus more on the code and get real work done without worrying about managing servers. Many people prefer the term FaaS (Function-as-a-Service) to serverless, because what essentially functions are the unit of application logic in this realm. Auth0's Webtask is a hassle-free serverless platform to deploy and run your functions.

At Auth0, we tend to solve most of our problems using Webtasks. Here's an example of how we used them to create a Slack bot to tackle a pressing need we had.

Go Beyond Basic Slack and Zendesk Integration

Not to brag, but Auth0 is known for its wonderful customer service. We use Zendesk to manage the hundreds of customer queries we get every day. Being an integral part of our day-to-day work, we use multiple Zendesk-to-Slack integrations to make sure that all customer queries are responded in a timely manner.

For a long time, we had a need to be able to mention someone else in a ticket. The only out-of-the box option was to add her email to the CCs list, but this had its own drawbacks. What we wanted to achieve was an integration that would go hand-in-hand with our primary method of communication — Slack. Zendesk has some basic Slack integration options, but it's not programmable enough to handle mentions.

Then we thought, can we use a webtask to achieve this?

Webtasks to the Rescue

Of course we can! Whenever you want to do automate something, you can put a webtask there. We quickly implemented a Zendesk mentions to Slack integration in a webtask. No need to procure any servers. No worrying about how much computing power or uptime this would need. All we had to do was write the code and create a trigger in Zendesk.


Here's an overview of the data flow of our app:

Slack and Zendesk Integration

Peter, a Zendesk agent, mentions his colleague Rodrigo as <@rodrigo>. That's Rodrigo's Slack username. A Zendesk trigger picks up the comment with a mention and does an HTTP POST request to our webtask. The webtask analyzes the comment and determines the exact Slack user (@rodrigo in this case). It then calls the Slack API to send a direct message to @rodrigo with details about the comment. If Peter mentioned a Slack channel name instead of a username, it would be sent to that specific Slack channel.

To set this up, we need to do the following:

  • Create a Slackbot.
  • Write and deploy the webtask.
  • Create a trigger in Zendesk.

1. Create a Slackbot

Simply visit this page and enter a name for the bot. A new Slack bot will be created. After creating, an API token will be assigned to the bot. Make a note of this because we will need it in the next step.

2. Create the Webtask

Now the fun begins. First, if you haven't set up the webtask CLI, follow the three simple steps in this webtask.io page. Once you're done it's time to write the code.

Here's the code we used at Auth0. You may edit it to your liking.

'use latest';

const request = require('request');
const _ = require('lodash@4.8.2');

const baseURL = 'https://slack.com/api/';
const usersListEndpoint = 'users.list';
const imOpenEndpoint = 'im.open';
const chatPostEndpoint = 'chat.postMessage';
let token;

/* Call the given endpoing in Slack API */
const callAPI = (endpoint, form, cb) => {
  request.post(baseURL + endpoint, {form}, (err, res, body) => {
    if (err) return cb(err);

    body = JSON.parse(body);
    if (!body.ok) return cb(body.error);

    return cb(null, body);

/* Find Slack ID of the user with given username */
const findUser = (username, cb) => {
  callAPI(usersListEndpoint, {token}, (err, body) => {
    if (err) return cb(err);

    const user = _.find(body.members, {name: username});

    if (!user) return cb(`User ${username} not found`);
    cb(null, user.id);

/* Open a direct msg channel with given Slack user id */
const openIM = (user, cb) => {
  callAPI(imOpenEndpoint, {token, user}, (err, body) => {
    if (err) return cb(err);
    cb(null, body.channel.id);

/* Post message to specified Slack channel */
const postMsg = (channel, data, cb) => {
  const obj = {
    title: `#${data.id} | ${data.title}`,
    title_link: 'https://auth0.zendesk.com/agent/tickets/' + data.id,
    fields: [
      {title: 'Mentioned by', value: data.author},
      {title: 'Comment', value: data.comment},
      {title: 'Tags', value: data.tags}
  callAPI(chatPostEndpoint, {
    as_user: false,
    username: 'Zendesk Mentions Bot',
    icon_url: 'http://i.imgur.com/IhN4IzR.png?1',
    text: 'You were mentioned in this ticket:',
    attachments: JSON.stringify([obj])
  }, (err, body) => {
    if (err) { console.log(err); return cb(err); }

/* Extract mentioned user's name from comment */
const extractName = (comment) => {
  const start = comment.indexOf('<@') + 2;
  const end = comment.substr(start).indexOf('>');
  return comment.substr(start, end);

module.exports = (context, cb) => {

  // Slack bot token
  token = context.data.BOT_TOKEN;

  const name = extractName(context.data.comment).toLowerCase();

  findUser(name, (err, id) => {
    if (err) {
      // If no such user, assume it's a channel
      return postMsg(name, context.data, cb);

    return openIM(id, (err, channelId) => {
      if (err) { console.log(err); return cb(); }
      else postMsg(channelId, context.data, cb);


Less than 100 lines of code!

The entry point to the code is the line starting with module.exports = (context, cb) => {. When the webtask is triggered, this function will be executed, which will in turn call the rest of the functions when necessary.

For security reasons, we add the bot's token as a configuration (as described below) instead of in the code. Then we find the mentioned name from the text of the comment. We check Slack to see if such a user exists. If not, we assume it's a channel name and post it into the channel with that name. If a user is found, we open an IM channel with that user and post the message.

Save this code in a file named slackmention.js and enter the following command to deploy it as a webtask:

wt create --secret BOT_TOKEN=<Slack bot token from step 1 goes here> slackmention.js

After the webtask is deployed the CLI will present you with its unique URL. We will use this in the next step.

3. Create a Trigger in Zendesk

The last step is to tell Zendesk to call our webtask when it sees a comment that might have a mention in it. You need to be an admin in Zendesk to do this. If you are not, reach out to your friendly Zendesk admin and don't forget to give them a cookie.

In Zendesk, go to Settings > Extensions and create a new HTTP target with the webtask's URL as URL (obtained in Step 2), POST as the method and JSON as the content type.

Now go to Settings > Triggers and create a new trigger with 'Ticket: Comment text...' as the condition, "Contains the following string" as the op, and <@ as the string. The performed action should be 'Notifications: Notify target' set to the HTTP Target created above. Set the JSON body as follows:

{ "id": "{{ticket.id}}", "title": "{{ticket.title}}", "comment": "{{ticket.latest_comment}}", "author": "{{ticket.latest_comment.author.name}}", "tags": "{{ticket.tags}}" }

Test It!

Now we are all done. To test our new setup, add the following comment in a new (or existing) Zendesk ticket. This could either be a public or an internal comment.

Hello <@thameera>!

Replace thameera with your Slack username, of course. If you performed all the steps in order, you will get a Slack notification like this:

Slack mention in the Zendesk ticket

That's it! You can customize the trigger and the webtask to suit your company's preferences and deploy your own Zendesk-to-Slack mentions implementation in a few minutes. For example, you can modify it to send an email or send a DM via HipChat if that's your chat application of choice.


The next time you have the need to create a bot, automate something or write any program, keep in mind that you can use a webtask to say no to yak shaving and focus only on your code.

new ,slack ,bot ,integration ,basic ,serverless

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