Slack Webhooks Guide

Slack Webhooks Guide

This is a guide on Slack Webhooks and using AWS Lambda to send messages to Slack via the webhook. The Slack webhook is a feature that allows external applications to send messages directly to Slack channels. It provides a unique URL that acts as a bridge between the application and Slack, enabling automated messages, notifications, or data updates to be posted in real-time. Webhooks are a powerful tool for integrating external systems with Slack, facilitating seamless communication and collaboration within teams.

Setup the Webhook

To setup a webhook simply do the following.

1. Go to the Slack API website: https://api.slack.com/apps and sign in with your Slack account.
2. Create a new Slack app by clicking on the “Create an App” button.
3. Click “From Scratch” to create an app from scratch.
4. Give your app a name and select the workspace where you want to use the webhook and click create app.
5. Once the app is created, in the left sidebar, click on “Incoming Webhooks” and toggle the switch to activate it.
6. Click on “Add New Webhook to Workspace” to generate a new webhook URL.
7. Select the Channel that you want your app to post messages to, then click Allow.
8. Now you should have the webhook URL created and be able send messages to. It should look like this:

   https://hooks.slack.com/services/XXXXXXX/XXXXXXXX/XXXXXXXXXXXXX
   

Use the Webhook

To use the webhook, simply load the following code into your Lambda function and post a “Hello World” message to the webhook. Be sure to replace the webhook_url with your webhook URL. See Lambda Basics Tutorial for instructions on how to set up an AWS Lambda.

1. Add the following Slack Utility code to your lambda function.

   import json
   import urllib3
   #import certifi
   #http = urllib3.PoolManager(ca_certs=certifi.where()) #See post: https://stackoverflow.com/a/72878639
   http = urllib3.PoolManager() 
   #
   class SlackUtility:
   #
    @classmethod
    def post(self, text, webhook_url):
        request = {'text': text}
        encoded_request = json.dumps(request).encode('utf-8')
        return http.request('POST', webhook_url, body=encoded_request)
   

2. Use the Slack Utility to post this message to Slack with your lambda handler.

   def lambda_handler(event, context):
    text = 'Hello World'
    webhook_url = 'https://hooks.slack.com/services/XXXXXXX/XXXXXXXX/XXXXXXXXXXXXX'
    return SlackUtility.post(text, webhook_url)
   

Conclusion

Now you know the basics of setting up and using Slack webhooks with Python to post messages to your Slack channels. Remember to keep your webhook URL secure as it provides access to post messages to your Slack workspace.