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.

Tools used in this project

  • Slack:
  • GitHub:
  • Amazon API Gateway & Lambda

Slack Setup

  1. Setup a Slack team if you don’t have one to use.
  2. Create a new channel (or skip this step to use an existing channel that the messages will appear.)

    Create a Slack Channel

  3. From settings choose “Add an app or integration”.

    Add an app or integration

  4. In the textbox, type and choose “Incoming Webhooks”

    Incoming Webhooks

  5. If this is the first Webhook created, click on “install”, otherwise “configure”.

  6. Configure a new Webhook into the desired channel.

    Configure a new Webhook

  7. Complete and save the form. Note the Webhook URL for use later.

    Webhook form

AWS Lambda Setup

  1. Make sure you note the region you are using.

    Lambda Region

  2. Create a new Lambda Function; skip selecting a blueprint.

  3. Configure the Lambda function:

    • 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.

      Replace Code

    • (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.

      Lambda default IAM Role

    • 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.

      Review and Create Lambda

  4. 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:

    Lambda will prompt for inputs

  5. 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:

    Test button Slack response

  6. Now your Lambda function is ready to go, let’s connect to an API Gateway!

AWS API Gateway Setup

  1. Setup a New API Gateway or use an existing Gateway if you have one setup.
  2. Create a new Resource. Enter a name and use the default for the resource path.
  3. Click on the new Resource and create a new Method > Post
  4. Choose Lambda Function > us-west-2 > smylee_github_slack_alert, save. After saving, a permissions prompt will popup choose OK.

    API Gateway Lambda Setup

  5. Click on the method function just created and four boxes will appear on the right side, click the Test Icon.

    Test API Gateway

  6. In the Request Body textarea, paste the same payload used for the pull request event. (

    Request Body textarea

  7. 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!

    Test button Slack response

  8. Now deploy the API from Actions > Deploy API.

    Deploy API

  9. In Deployment Stage, Choose [New Stage], in the stage name enter “prod” (this will be part of the API url.)

    Deploy API Setup

  10. Once the API is created, within Stages from the left side, drill down to the resource and click the method.

    Deploy URL

  11. This will display an “Invoke URL”, copy this URL and we’ll use it in the GitHub Setup section.

    Invoke URL

GitHub Setup

  1. Create a new repository, add some files.
  2. In the settings for the repository, go to Webhooks & Services > Add Webhook.

    Add Webhook

  3. 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

    GitHub Webhook

  4. Save webhook.

Try it out!

  1. In your repo, create a new file, name the file, add some text, and create a new branch, and propose new file to save.

    Create new file in repo

  2. Click the Create a pull request button.

    Create pull request

  3. If you have your Slack open, you should’ve received a message in the channel!

    Receive Slack Message

  4. Try closing, opening, and merging the pull request from GitHub and you should receive messages for each action (merge will report closed).

    Close,Open,Merge Repo


  • 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.

    CloudWatch Logs

AWS Costs for creating this project

  • 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.