python

The Simple GraphQL Service

This is an example CDK stack to deploy The Simple GraphQL Service inspired by Thorsten Hoeger's contributions to the CDK AppSync Module example

An advanced version of this pattern was talked about by Heitor Lessa at re:Invent 2019 as "The Cherry Pick".

• Youtube Recording
• Static Slides

This is the most basic of AppSync implementations and would have to be hardened before production use. e.g. cognito user pools configured

Note, never print your API Key to the logs in a production system. This was added to make learning AppSync and GraphQL easier. If you want to use this pattern in a production system remove the two cloudformation outputs

Testing

1. After CDK Deploy, capture outputs from the log.

TheSimpleGraphqlServiceStack: deploying...
TheSimpleGraphqlServiceStack: creating CloudFormation changeset...

   TheSimpleGraphqlServiceStack

Outputs:
TheSimpleGraphqlServiceStack.APIKey = <API Key>
TheSimpleGraphqlServiceStack.Endpoint = https://<endpoint URL>.appsync-api.us-east-1.amazonaws.com/graphql

2. Setup Postman as outlined in Postman's Using GraphQL Instructions

3. Set POST request URL, x-api-key and Content-Type

• x-api-key = 'your API Key'
• Content-Type = application/graphql

4. Execute Mutations and Queries to exercice resolvers to dynamo and Lambda datasources

// Inserts to Dynamo
mutation add {
  addCustomer(customer: { name: "CDKPatterns"}) {
    id
    name
  }
}

// Queries the Dynamo DB
query getCustomers {
  getCustomers{id name}
}

// Executes the Lambda
query getLoyalty {
  getLoyaltyLevel { level }
}

CDK Python Useful Commands

The cdk.json file tells the CDK Toolkit how to execute your app.

This project is set up like a standard Python project. The initialization process also creates a virtualenv within this project, stored under the .env directory. To create the virtualenv it assumes that there is a python3 (or python for Windows) executable in your path with access to the venv package. If for any reason the automatic creation of the virtualenv fails, you can create the virtualenv manually.

To manually create a virtualenv on MacOS and Linux:

$ python -m venv .env

After the init process completes and the virtualenv is created, you can use the following step to activate your virtualenv.

$ source .env/bin/activate

If you are a Windows platform, you would activate the virtualenv like this:

% .env\Scripts\activate.bat

Once the virtualenv is activated, you can install the required dependencies.

$ pip install -r requirements.txt

At this point you can now synthesize the CloudFormation template for this code.

$ cdk synth

To add additional dependencies, for example other CDK libraries, just add them to your setup.py file and rerun the pip install -r requirements.txt command.

Useful commands

• cdk ls list all stacks in the app
• cdk synth emits the synthesized CloudFormation template
• cdk deploy deploy this stack to your default AWS account/region
• cdk diff compare deployed stack with current state
• cdk docs open CDK documentation

Enjoy!