Starry Wisdom

Chalice

Chalice is the “Python Serverless Microframework for AWS”. It allows quick and simple development of REST APIs, and comes with a a deploy tool that does all the work necessary to deploy your lambda, as well as create policy and integrate with the API Gateway. Let’s start out by creating an example app:

$ chalice new-project example-app

And then we can quickly create a simple app that reads in a couple of parameters and creates a JSON response. Note the use of the decorator to declare the route and method:

from chalice import Chalice app = Chalice(app_name='example-app') @app.route('/customer/{customer_id}/order/{order_id}', methods=['PUT']) def register_order(customer_id, order_id):     # imagine inserting this into Dynamo, etc...     return {'customer':customer_id,             "order_id": order_id }

Deploying this as simple as:

$ chalice deploy
Creating role: example-app-dev
Creating deployment package.
Creating lambda function: example-app-dev
Initiating first time deployment.
Deploying to API Gateway stage: api
https://id.execute-api.us-west-2.amazonaws.com/api/

At which point you can access it like this:

$ curl -X PUT https://id.execute-api.us-west-2.amazonaws.com/api/customer/customer01/order/123183123
{"customer": "customer01", "order_id": "123183123"}

See the tutorial, which is quite good, for more information on what you can do inside the apps (such as tying in other AWS services).

Enter Terraform

But what if you want to use Terraform to deploy your infrastructure? The first step is to create a deployment package:

$ chalice package .
Creating deployment package.
$ ls -l deployment.zip
-rw-r--r-- 1 nchazin staff 9022 Oct 18 22:24 deployment.zip

And now we’re ready to code up our terraform. We’ll begin by defining a few variables, which we can store values for in a terraform.tfvars file.

Next we’ll define the lambda itself, along with its associated role, and a policy which allows us to log and monitor with Cloudwatch:

 

 

With our lambda set up, we can create out API Gateway:

 

The final piece is the permission that allows our API Gateway to access the lambda. Note that you can be more specific and limit acess to the specific API method and path if desired by adding them to the source_arn.

Now we can install our API:

And query it at both the stage and prod endpoints: