aws-serverless-api-template

Serverless Lambda Template

This is the template we use when developing new serverless python code on AWS. It includes a number of basic but simple improvements to the standard aws-python3 template that serverless offers out of the box:

• ./common: Common configurations for improved readability in yml files
• ./local_server: A dockerized flask application which is useful if you're building an API. This can be connected to our local_mysql container.
• ./modules: Reusable, tested python code for common things such as database I/O.
• ./functions: This is where your lambda handlers should go. We include an example of one function that calls into one of our modules.
• ./tests: Pytest tests for testing modules in ./modules

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Usage

To get started, you need to have serverless installed: npm install -g serverless

Then, to create a new project using our template, run:

sls create --template-url https://github.com/smartshare-labs/aws-serverless-api-template --path NEW_PROJECT_PATH

To deploy your code to lambda:

sls deploy --stage dev

or for production:

sls deploy --stage prod

Refer to the serverless documentation (https://serverless.com/framework/docs/) for more useful commands.

Note: A good rule of thumb when developing is to keep core application logic out of your lambda handlers. This is the pattern we try to employ with the ./modules folder. Keeping your complexity in tested, reusable modules such as these allows for simple integration testing of the lambda handlers themselves.

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Using the local flask server

We assume you already have docker installed. From the ./local_server folder, run docker-compose up --build. For each lambda handler that you want to expose in the local flask app, add a route in ./local_server/app.py that forwards the appropriate event/context to your function.

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Testing

Write your tests in the ./tests folder. Then:

1. Create a virtual environment in ./tests: virtualenv -p python3 venv
2. Source it: source venv/bin/activate
3. Install requirements: pip install -U requirements.txt

Finally, to run tests: python -m pytest tests from the root directory.