Create an API Gateway for Cloud Function

Okay, let's create an API Gateway to expose your outofstock Cloud Function. Follow these steps:

1. Set Environment Variables

First, set the necessary environment variables in your Cloud Shell. Make sure to replace YOUR_PROJECT_ID with your actual Google Cloud Project ID.

export CONFIG_ID="outofstock-api-config"
export API_ID="outofstock-api"
export GATEWAY_ID="outofstock-gateway"
export PROJECT_ID=$(gcloud config get-value project) # This will get your current project ID
export REGION="us-central1" # Ensure this matches the region where you deployed your Cloud Function

2. Create the OpenAPI Specification File

Create a new directory named gateway and then create a file named outofstock.yaml inside it. You can use the mkdir and touch commands, then open the file with an editor like nano or vi.

mkdir gateway
cd gateway
nano outofstock.yaml

Paste the following content into outofstock.yaml. IMPORTANT: You must replace YOUR_CLOUD_FUNCTION_TRIGGER_URL with the actual trigger URL of your deployed outofstock Cloud Function. You can find this URL in the Cloud Functions console, or by running the command:

gcloud functions describe outofstock --region us-central1 --format='value(serviceConfig.uri)'

swagger: "2.0"
info:
  title: Outofstock API
  description: API Gateway for the outofstock Cloud Function.
  version: 1.0.0
schemes:
  - https
produces:
  - application/json
paths:
  # Add your paths here

Save and exit the editor (Ctrl+X, Y, Enter for nano).

3. Enable the API Gateway Service

If you haven't already, enable the API Gateway service:

gcloud services enable apigateway.googleapis.com

4. Create the API

gcloud api-gateway apis create ${API_ID} --project=${PROJECT_ID}

5. Create the API Configuration

gcloud api-gateway api-configs create ${CONFIG_ID} \
  --api=${API_ID} \
  --openapi-spec=outofstock.yaml \
  --project=${PROJECT_ID} \
  --display-name="Outofstock Config V1"

6. Create the API Gateway

gcloud api-gateway gateways create ${GATEWAY_ID} \
  --api=${API_ID} \
  --api-config=${CONFIG_ID} \
  --location=${REGION} \
  --project=${PROJECT_ID}

7. Verify the Gateway and Get its Hostname

This command will show you the status and the defaultHostname of your deployed gateway. It might take a few minutes for the gateway to become fully deployed.

gcloud api-gateway gateways describe ${GATEWAY_ID} \
  --location=${REGION} \
  --project=${PROJECT_ID}

Look for the defaultHostname in the output. It will be a URL like https://outofstock-gateway-XXXXXX.REGION.gateway.dev.

8. Test the Deployed API Gateway

Once you have the defaultHostname, open a web browser and navigate to:

YOUR_GATEWAY_HOSTNAME/outofstock

For example:

https://outofstock-gateway-XXXXXX.us-central1.gateway.dev/outofstock

Verify that JSON data is returned as expected from your Cloud Function. You should see the out-of-stock products listed.

Troubleshooting

API Already Exists Error

If you encounter this error:

ERROR: (gcloud.api-gateway.apis.create) ALREADY_EXISTS: Resource 'projects/qwiklabs-gcp-04-9c7c4b892ed8/locations/global/apis/outofstock-api' already exists

This means that the API with the ID outofstock-api has already been created in your project. You do not need to create it again. You can proceed directly to the next step: Create the API Configuration.

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