Serverless REST API on Google Cloud Functions

A minimal Serverless REST API with three endpoints (/hello, /users, /stats) built using:

• Google Cloud Functions (1st-gen)
• API Gateway
• Deployment Manager (IaC for automation)

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Project Structure

serverless-api/
│
├── functions/
│   ├── hello/          # Code for /hello endpoint
│   │   ├── main.py
│   │   └── requirements.txt
│   │
│   ├── users/          # Code for /users endpoint
│   │   ├── main.py
│   │   └── requirements.txt
│   │
│   └── stats/          # Code for /stats endpoint
│       ├── main.py
│       └── requirements.txt
│
├── apigateway/
│   └── api-config.yaml # OpenAPI spec for API Gateway
│
├── deployment-manager/
│   └── deployment.yaml # Deployment Manager template for hello\_world
│
└── README.md

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Endpoints (Deployed)

1. GET /hello
   Returns:

   Hello from Yash’s first GCP function!
   

2. GET /users Returns:

   { "users": ["alice", "bob", "carol"] }

3. GET /stats Returns:

   { "active_users": 23, "uptime": "99.9%" }

Once you deploy via API Gateway, all three will live under one base URL:

https://<GATEWAY_ID>-uc.a.run.app

So you can call:

curl https://<GATEWAY_ID>-uc.a.run.app/hello
curl https://<GATEWAY_ID>-uc.a.run.app/users
curl https://<GATEWAY_ID>-uc.a.run.app/stats

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How to Deploy (MVP)

1. Prerequisites

• A GCP project with billing enabled (e.g. YOUR_PROJECT_ID)

• GCP APIs enabled:

  • Cloud Functions API
  • API Gateway API
  • Cloud Deployment Manager API
  • (Optional) Cloud Build API

• Installed and initialized Google Cloud SDK (gcloud init)

2. Deploy Cloud Functions (1st-gen)

From serverless-api root:

# 2.1 Deploy hello_world
gcloud functions deploy hello_world \
  --runtime python311 \
  --trigger-http \
  --entry-point hello_world \
  --allow-unauthenticated \
  --region us-central1 \
  --source=functions/hello \
  --no-gen2

# 2.2 Deploy get_users
gcloud functions deploy get_users \
  --runtime python311 \
  --trigger-http \
  --entry-point get_users \
  --allow-unauthenticated \
  --region us-central1 \
  --source=functions/users \
  --no-gen2

# 2.3 Deploy get_stats
gcloud functions deploy get_stats \
  --runtime python311 \
  --trigger-http \
  --entry-point get_stats \
  --allow-unauthenticated \
  --region us-central1 \
  --source=functions/stats \
  --no-gen2

Wait for each deployment to complete. Note each function’s URL.

3. Set Up API Gateway

1. Edit apigateway/api-config.yaml:

   • Replace YOUR_PROJECT_ID in each address: field with your real project ID.

2. Create the API, config, and gateway:

   # 3.1 Create the API resource
   gcloud api-gateway apis create serverless-api \
     --project=YOUR_PROJECT_ID
   
   # 3.2 Create the API config from the OpenAPI spec
   gcloud api-gateway api-configs create serverless-api-config \
     --api=serverless-api \
     --openapi-spec=apigateway/api-config.yaml \
     --project=YOUR_PROJECT_ID
   
   # 3.3 Create the Gateway to serve that API
   gcloud api-gateway gateways create serverless-gateway \
     --api=serverless-api \
     --api-config=serverless-api-config \
     --location=us-central1 \
     --project=YOUR_PROJECT_ID

3. Once the gateway is up (it may take ~1–2 minutes), note the “defaultHostname” it prints, e.g.:

   https://<GATEWAY_ID>-uc.a.run.app
   

4. Test each route:

   curl https://<GATEWAY_ID>-uc.a.run.app/hello
   curl https://<GATEWAY_ID>-uc.a.run.app/users
   curl https://<GATEWAY_ID>-uc.a.run.app/stats

4. (Optional) Automate hello_world with Deployment Manager

To automate just the hello_world function:

1. Ensure you have a GCS bucket (replace YOUR_BUCKET_NAME):

   gsutil mb -p YOUR_PROJECT_ID gs://YOUR_BUCKET_NAME

2. Zip and upload your function source:

   cd functions/hello
   zip -r hello_source.zip main.py requirements.txt
   gsutil cp hello_source.zip gs://YOUR_BUCKET_NAME/
   cd ../../

3. Edit deployment-manager/deployment.yaml and replace:

   • YOUR_PROJECT_ID
   • YOUR_BUCKET_NAME in sourceArchiveUrl: gs://YOUR_BUCKET_NAME/hello_source.zip

4. Create or update the deployment:

   gcloud deployment-manager deployments create hello-deployment \
     --config=deployment-manager/deployment.yaml \
     --project=YOUR_PROJECT_ID
   
   # If you modify the code & reupload the zip:
   gcloud deployment-manager deployments update hello-deployment \
     --config=deployment-manager/deployment.yaml \
     --project=YOUR_PROJECT_ID

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