WackoBot-Serverless

Round 2 of making a Discord Bot, this time it's ✨ serverless ✨.

Architecture

This project contains source code and supporting files for a serverless application that you can deploy with the SAM CLI. It includes the following files and folders.

• discord-bot/ - Code for the application's Lambda function along with the handlers, tests and sample events.
• events/ - Lambda invocation events. I haven't included this folder as it includes sample events with signed requests.
• tests/ - Tests for the application code.
• template.yaml - A template that defines the application's AWS resources.

The application uses several AWS resources, including Lambda functions and an API Gateway API. These resources are defined in the template.yaml file in this project. You can update the template to add AWS resources through the same deployment process that updates your application code.

Deploy the application

The Serverless Application Model Command Line Interface (SAM CLI) is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda. It can also emulate your application's build environment and API.

To use the SAM CLI, you need the following tools.

• SAM CLI - Install the SAM CLI
• Python 3 installed
• Docker - Install Docker community edition

You will need to supply your own Bot tokens, client IDs, etc. in an env.json file. You can see the sample_env.json to see the required information.

To build and deploy your application for the first time, run the following in your shell:

# Validate the configuration
sam validate 

# Build the application (.aws-sam/, etc.)
sam build

# Deploy the application
sam deploy --guided

The first command will validate the SAM template. The second command will build the source of your application. The third command will package and deploy your application to AWS, with a series of prompts:

• Stack Name: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
• AWS Region: The AWS region you want to deploy your app to.
• Confirm changes before deploy: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
• Allow SAM CLI IAM role creation: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modifies IAM roles, the CAPABILITY_IAM value for capabilities must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass --capabilities CAPABILITY_IAM to the sam deploy command.
• Save arguments to samconfig.toml: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run sam deploy without parameters to deploy changes to your application.
• ListenFunction may not have authorization defined, Is this okay?: Guided deployments will prompt to confirm when you have a publicly accessible API Gateway endpoint. If you do not want the endpoint to be publicly accessible without authorization, you can add ApiFunctionAuth settings to the Api event. See the documentation for details.

You can find your API Gateway Endpoint URL in the output values displayed after deployment.

Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called sam logs. sam logs lets you fetch logs generated by your deployed Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

NOTE: This command works for all AWS Lambda functions; not just the ones you deploy using SAM.

discord-bot$ sam logs -n ListenFunction --stack-name discord-bot --tail

You can find more information and examples about filtering Lambda function logs in the SAM CLI Documentation.

Tests

Tests are defined in the tests folder in this project. Use PIP to install the test dependencies and run tests.

You will need to gather event data for your own application for the necessary tests. I have included a sample_event.json so that you can see the structure. I haven't included my own events as they do contain signed requests to my own API 😥.

discord-bot$ pip install -r tests/requirements.txt --user
# integration test, requiring deploying the stack first.
# Create the env variable AWS_SAM_STACK_NAME with the name of the stack we are testing
discord-bot$ AWS_SAM_STACK_NAME=<stack-name> python -m pytest tests/integration -v

# integration tests can be checked locally with the local lambda function running docker

# Start API Gateway docker environment
discord-bot$ sam local start-api

# Run local integration tests
discord-bot$ AWS_SAM_STACK_NAME=<stack-name> RUNNING_LOCAL=true python -m pytest tests/integration -v

Cleanup

To delete the sample application that you created, use the AWS CLI. Assuming you used your project name for the stack name, you can run the following:

discord-bot$ sam delete