Getting started with API Gateway and App Engine

This page shows you how to set up API Gateway to manage and secure an App Engine backend service.

Task List

Use the following task list as you work through the tutorial. All tasks are required to deploy an API gateway for your App Engine backend service.

1. Create or select a Google Cloud project.
2. If you haven't deployed your own App Engine, deploy a sample app. See Before you begin.
3. Enable the required API Gateway services.
4. Configure IAP to secure your app. See Configure IAP.
5. Create an OpenAPI spec that describes your API, and configure the routes to your App Engine. See Creating an API config.
6. Deploy an API gateway using your API config. See Deploying an API Gateway.
7. Track activity to your apps. See Tracking API activity.
8. Avoid incurring charges to your Google Cloud account. See Clean up.

Before you begin

1. In the Google Cloud console, go to the Dashboard page and select or create a Google Cloud project.

   Go to the Dashboard page

   Note: If you don't plan to keep the resources you create in this tutorial, create a new project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

2. Make sure that billing is enabled for your project.

   Enable billing

3. Make a note of the project ID you want to use for this tutorial. On the rest of this page, this project ID is referred to as PROJECT_ID.

4. Download and install the Google Cloud CLI.

   Download the gcloud CLI

5. Update gcloudcomponents:

   gcloud components update

6. Set the default project. Replace PROJECT_ID with your Google Cloud project ID:

   gcloud config set project PROJECT_ID

7. If you haven't deployed your own App Engine app, follow the steps in the App Engine Quickstart for your language to use the Google Cloud CLI to select or create a Google Cloud project and deploy a sample app. Make a note of the app URL, as well as the region and project ID where your app is deployed.

Enabling required services

API Gateway requires that you enable the following Google services:

Name	Title
apigateway.googleapis.com	API Gateway API
servicemanagement.googleapis.com	Service Management API
servicecontrol.googleapis.com	Service Control API

To confirm that the required services are enabled:

gcloud services list

If you do not see the required services listed, enable them:

gcloud services enable apigateway.googleapis.com
gcloud services enable servicemanagement.googleapis.com
gcloud services enable servicecontrol.googleapis.com

For more information about the gcloud services, see gcloud services.

Configuring IAP to secure your app

In order to secure your App Engine app, you must use the Identity Aware Proxy (IAP) to ensure that requests are authenticated. This process includes specifying the members who should be granted the IAP-secured Web App User role required for the project.

Follow the steps to Enable IAP, and ensure that you are able to sign in to your application.

Note: Once IAP is enabled for your App Engine app, make sure to note the OAuth 2.0 client_id. This is used as the IAP_CLIENT_ID later in this tutorial. To locate the OAuth 2.0 client_id for your App Engine app, go to the APIs & Services > Credentials page in the Google Cloud console. Copy the Client ID for your application from the OAuth 2.0 Client IDs section of the page.

Creating an API config

Before API Gateway can be used to manage traffic to your deployed App Engine backend, it needs an API config.

You can create an API config using an OpenAPI spec that contains specialized annotations to define the chosen API Gateway behavior. You will need to add a Google-specific field that contains the URL for each App Engine app so that API Gateway has the information it needs to invoke an app.

1. Create a text file called openapi2-appengine.yaml. (For convenience, this page refers to the OpenAPI spec by that filename, but you can name it something else if you prefer.)
2. List each of your apps in the paths section of the openapi2-appengine.yaml file, as shown:

   # openapi2-appengine.yaml
   swagger: '2.0'
   info:
     title: API_ID optional-string
     description: Sample API on API Gateway with an App Engine backend
     version: 1.0.0
   schemes:
     - https
   produces:
     - application/json
   paths:
     /hello:
       get:
         summary: Greet a user
         operationId: hello
         x-google-backend:
           address: APP_URL
           jwt_audience: IAP_CLIENT_ID
         responses:
           '200':
             description: A successful response
             schema:
               type: string

3. In the title field, replace API_ID with the name of your API and replace optional-string with a brief description of your choosing. If your API does not already exist, the command to create the API Config will also create the API with the name you specify. The value of the title field is used when minting API keys that grant access to this API. See API ID requirements for API naming guidelines.
4. In the address field in the x-google-backend section, replace APP_URL with the actual URL of your App Engine service (the full path of the called API). For example, https://myapp.an.r.appspot.com/hello.

   Replace IAP_CLIENT_ID with the OAuth Client ID you created when you set up IAP.

5. Enter the following command, where:
   • CONFIG_ID specifies the name of your API config.
   • API_ID specifies the name of your API. If the API does not already exist then this command creates it.
   • PROJECT_ID specifies the name of your Google Cloud project.
   • SERVICE_ACCOUNT_EMAIL specifies the service account used to sign tokens for backends with authentication configured.

   gcloud api-gateway api-configs create CONFIG_ID \
     --api=API_ID --openapi-spec=openapi2-appengine.yaml \
     --project=PROJECT_ID --backend-auth-service-account=SERVICE_ACCOUNT_EMAIL

   This operation may take several minutes to complete as the API config is propagated to downstream systems. Creation of a complex API config could take up to ten minutes to complete successfully.

6. After the API config is created, you can view its details by running this command:

   gcloud api-gateway api-configs describe CONFIG_ID \
     --api=API_ID --project=PROJECT_ID

Deploying an API gateway

Now you can deploy your API on API Gateway. Deploying an API on API Gateway also defines an external URL that API clients can use to access your API.

Run the following command to deploy the API config you just created to API Gateway:

gcloud api-gateway gateways create GATEWAY_ID \
  --api=API_ID --api-config=CONFIG_ID \
  --location=GCP_REGION --project=PROJECT_ID

where:

• GATEWAY_ID specifies the name of the gateway.
• API_ID specifies the name of the API Gateway API associated with this gateway.
• CONFIG_ID specifies the name of the API config deployed to the gateway.

• GCP_REGION is the Google Cloud region for the deployed gateway.

  Note: Allowed values are:

  • asia-northeast1
  • australia-southeast1
  • europe-west1
  • europe-west2
  • us-east1
  • us-east4
  • us-central1
  • us-west2
  • us-west3
  • us-west4

• PROJECT_ID specifies the name of your Google Cloud project.

On successful completion, you can use the following command to view details about the gateway:

gcloud api-gateway gateways describe GATEWAY_ID \
  --location=GCP_REGION --project=PROJECT_ID

Note the value of the defaultHostname property in the output of this command. This is the hostname portion of the gateway URL you use to test your deployment in the next step.

Testing your API deployment

Now you can send requests to your API using the URL generated upon deployment of your gateway.

Enter the following curl command, where:

• DEFAULT_HOSTNAME specifies the hostname portion of your deployed gateway URL. The value of defaultHostname can be found in the output of the gateways describe command shown above.
• hello is the path specified in your API config.

curl https://DEFAULT_HOSTNAME/hello

For example:

curl https://my-gateway-a12bcd345e67f89g0h.uc.gateway.dev/hello

You should see the following output:

My-AppEngineApp: Access denied for user [e-mail] requesting https://my-project.appspot.com/helloGET. If you should have access, contact [e-mail] and include the full text of this message.

Success! Your gateway is managing access to your App Engine backend service. To grant access to your App Engine app, you will need to configure a service account with the correct permissions for yourg ateway.

Tracking API activity

1. View the activity graphs for your API on the API Gateway page in the Google Cloud console. Click your API to view its activity graphs on the Overview page. It may take a few moments for the requests to be reflected in the graphs.

2. Look at the request logs for your API on the Logs Explorer page. A link to the Logs Explorer page can be found on the API Gateway page in the Google Cloud console.

   Go to the API Gateway page

   Once on the API Gateway page:
   1. Select the API to view.
   2. Click the Details tab.
   3. Click the link under Logs.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this quickstart, you can:

• Delete your gateways
• Delete your API

Alternatively, you can also delete the Google Cloud project used for this tutorial.