Magic Night Project - Part 1: GitHub Pull Request Alert on Slack

Description

When a GitHub pull request is made, it will trigger an alert on Slack. A magic night project provided by AWS User Group Hosted by MindTouch.

Setup a Slack team if you don’t have one to use.
Create a new channel (or skip this step to use an existing channel that the messages will appear.)
From settings choose “Add an app or integration”.
In the textbox, type and choose “Incoming Webhooks”
If this is the first Webhook created, click on “install”, otherwise “configure”.
Configure a new Webhook into the desired channel.
Complete and save the form. Note the Webhook URL for use later.

Name the function.
Choose “Python 2.7” as the Runtime.
Download and copy/paste the code into the textarea.
In the code, replace to the Webhook I mentioned in the Slack setup.
(optional) Choose a different emoji from the emjoi cheet sheet or change the username message in the code.
Use the default Handler (lambda_function.lambda_handler).
Create a new role with *Basic Execution Role.
- This will open a new window/tab; use the default IAM Role and Create a new Role Policy.
Leave the rest of the settings default. You can choose your own VPC, but I’m choosing “No VPC” in this configuration.
Review and Create.

Test the function. On first test, Lambda will prompt for inputs. You can copy/paste the (VERY LONG) sample payload for the Pull Request Event from: https://developer.github.com/v3/activity/events/types/#pullrequestevent
Save and test! If you have your Slack open, you should’ve received a message in the channel where you setup the incoming Webhook. If you used the sample payload data, it will look something like this:
Now your Lambda function is ready to go, let’s connect to an API Gateway!

Setup a New API Gateway or use an existing Gateway if you have one setup.
Create a new Resource. Enter a name and use the default for the resource path.
Click on the new Resource and create a new Method > Post
Choose Lambda Function > us-west-2 > smylee_github_slack_alert, save. After saving, a permissions prompt will popup choose OK.
Click on the method function just created and four boxes will appear on the right side, click the Test Icon.
In the Request Body textarea, paste the same payload used for the pull request event. (https://developer.github.com/v3/activity/events/types/#pullrequestevent)
Click the Test button and if you have your Slack open, you should’ve recived a message in the channel you setup the incoming Webhook!
Now deploy the API from Actions > Deploy API.
In Deployment Stage, Choose [New Stage], in the stage name enter “prod” (this will be part of the API url.)
Once the API is created, within Stages from the left side, drill down to the resource and click the method.
This will display an “Invoke URL”, copy this URL and we’ll use it in the GitHub Setup section.

Create a new repository, add some files.
In the settings for the repository, go to Webhooks & Services > Add Webhook.
In the Payload URL, enter the URL from the API Gateway we just deployed.
Under “Which events would you like to trigger this webhook?”, choose: Let me select individual events. > Pull request
Save webhook.

In your repo, create a new file, name the file, add some text, and create a new branch, and propose new file to save.
Click the Create a pull request button.
If you have your Slack open, you should’ve received a message in the channel!
Try closing, opening, and merging the pull request from GitHub and you should receive messages for each action (merge will report closed).

Now anytime a pull request is made on this repo it will alert you on Slack.
If you want to customize the message, make the change in the slack_message inside the Lambda function.
Troubleshooting note: Check your CloudWatch Logs /aws/lambda/< lambda function name > for messages that were logged.

AWS provides a lot of services for free for the first 12 months of sign up and beyond. More information can be found on AWS pricing pages.
Cost should be less than $0.10 to create this project.
Lambda pricing cost - Doesn’t start to charge until you’ve made 1 million requests and gone over 400,000 GB-Seconds (each billed separately.)
API Gateway pricing cost - Different for some regions, but all regions are billed per million calls received, plus the cost of data transfer out, in gigabytes. Plus you only pay for what you use.