🤖Buzz me in

The goals for this project were two-fold:

1. come up with a fully automated solution to buzz in folks in my (and yours!) building, and
2. have some fun with serverless: Twilio and AWS Lambda

There are costs involved here as you will need to purchase a Twilio number and pay for each SMS sent as well as call time. These costs are super low though.

Architecture

Development

I'm using Make as my task runner/build automation tool here.

Building and deployment steps are all managed by a single top-level Make target for each service:

• Twilio: their CLI tool along with any used plugins are installed in your local machine. To deploy to Twilio you can run make twilio.deploy

• AWS Lambda: because some dependencies are platform specific I opted to install them via Docker. To deploy to AWS Lambda you can run make aws.deploy

Deployment / Installation

IMPORTANT:

• At the moment steps below assume you are working from a Mac with homebrew installed.
• Bear in mind that this was a weekend project. I've automated some steps, but there is a lot that is manual yet as you will see.

Contributions are more than welcome to make this platform agnostic and to automate steps even further.

1 - Initial Twilio setup

1. Create a Twilio account
2. Purchase a Twilio phone number and add credits to it
3. Run make twilio.deploy — deployment will fail but this will install dependencies
4. Run twilio profiles:create and follow prompts to login and select a profile
5. Run make twilio.deploy again to deploy your function
6. Using the Twilio UI go into your phone number. Under "Voice & Fax" select options as follows:

• A Call Comes In: Function
• Service: buzz-me-in
• Environment: production
• Function Path: /buzzer-handler

7. You may call your Twilio number now to test the changes. You should hear "Opening the door" followed by the DTMF tones.

2 - AWS Lambda setup

1. Create an AWS account
2. Set up the AWS CLI in your host machine and log in
3. Create a role for the lambda function we will create, under AWS's IAM section. Copy the ARN.
4. Define the following env variables:

• DESTINATION_PHONE_NUMBERS: a comma separated list of numbers that will receive a SMS when the door is opened, e.g. +19991234567,+19991236789 or +19991234567 if a single number
• TWILIO_ACCOUNT_SID: your twilio account SID
• TWILIO_PHONE_NUMBER: the phone number your created with Twilio
• TWILIO_TOKEN: your twilio token
• AWS_ROLE_ARN: the ARN for the role you created previously

5. Invoke make aws.deploy
6. Using the AWS UI create an "API Gateway" trigger for the lambda function just created. The security mechanism should be "Open".
7. Copy the generated API endpoint and go back to the Twilio UI.

3 - Finalize Twilio setup

1. Go into your phone number again.
2. Under "Call status changes" paste your API endpoint from before.

That should be it. As a quick experiment, dial in to your Twilio number. A few seconds after the DTMF tones you should receive SMSs on the registered phone numbers.

You are ready to provide to the building manager your Twilio phone number for the buzzer.

License

The gem is available as open source under the terms of the Apache 2.0 License.