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# Implement webhooks with FastAPI and Lakebase Postgres

Learn how to build a webhook system to receive and store event data using FastAPI and Lakebase Postgres

Webhooks let services notify each other by sending HTTP requests when specific events occur. Your application receives the data as events happen instead of polling for updates.

In this guide, you'll learn how to implement a webhook system using FastAPI to receive event notifications and Lakebase Postgres to store and process the webhook data. We'll build a webhook receiver that handles events from GitHub.

## Prerequisites

To follow this guide, you need:

- [Python 3.9+](https://www.python.org/downloads/) installed
- Basic knowledge of Python and FastAPI
- A [Neon](https://console.neon.tech/signup) account
- [ngrok](https://ngrok.com/) or similar tool for exposing your local server (for testing)
- A [GitHub](https://github.com/) account (for testing the webhook)

## Create a Neon project

Start by creating a new Neon project:

1. Log in to the [Neon Console](https://console.neon.tech)
2. Click **New Project**
3. Enter a name for your project, like `webhook-receiver`
4. Select your preferred AWS region
5. Click **Create project**

Once your project is created, click **Connect** to view the connection details. Save them for the FastAPI application.

## Set up a FastAPI project

FastAPI is a Python web framework for building APIs. It's based on standard Python type hints and generates OpenAPI documentation automatically.

Set up a basic FastAPI project structure:

1. Create a new directory for your project and navigate to it:

```bash
mkdir webhook-receiver
cd webhook-receiver
```

2. Create a virtual environment and activate it:

```bash
python -m venv venv
source venv/bin/activate  # On Windows, use: venv\Scripts\activate
```

3. Install the required packages:

```bash
pip install fastapi uvicorn sqlalchemy asyncpg python-dotenv pydantic pydantic-settings httpx psycopg2-binary greenlet
```

4. Create a basic directory structure:

```bash
mkdir app
touch app/__init__.py
touch app/main.py
touch app/config.py
touch app/models.py
touch app/database.py
touch .env
```

5. Set up the environment variables by adding the following to the `.env` file:

```
DATABASE_URL=postgres://[user]:[password]@[hostname]/[database]?sslmode=require&channel_binding=require
WEBHOOK_SECRET=your_webhook_secret  # We'll use this later for verification
```

Replace the placeholders in the `DATABASE_URL` with your Neon connection details.

## Design the database schema

Before implementing the webhook receiver, design the database schema. For our GitHub webhook example, we'll create a table to store webhook events with the following fields:

- `id`: A unique identifier for each webhook event
- `event_type`: The type of event (e.g., "push", "pull_request")
- `delivery_id`: The unique ID provided by GitHub for the webhook delivery
- `signature`: The signature sent with the webhook for verification
- `payload`: The JSON payload of the webhook
- `processed`: A boolean indicating if the webhook has been processed
- `created_at`: When the webhook was received

Now, let's set up the database connection and models.

## Create the database models

First, let's set up the configuration file (`app/config.py`):

```python
# app/config.py
from pydantic_settings import BaseSettings
from dotenv import load_dotenv

load_dotenv()

class Settings(BaseSettings):
    database_url: str
    webhook_secret: str

    class Config:
        env_file = ".env"

settings = Settings()
```

Here, we're using `pydantic-settings` to load environment variables from the `.env` file.

Next, let's set up the database connection (`app/database.py`):

```python
# app/database.py
import ssl
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker, declarative_base
from app.config import settings
from urllib.parse import urlparse

# Setup SSL context
ssl_context = ssl.create_default_context()
ssl_context.check_hostname = False
ssl_context.verify_mode = ssl.CERT_NONE

# Parse the database URL to remove query parameters
# that can cause issues with asyncpg
parsed_url = urlparse(settings.database_url)
db_user = parsed_url.username
db_password = parsed_url.password
db_host = parsed_url.hostname
db_port = parsed_url.port or 5432
db_name = parsed_url.path.lstrip('/')

# Create an async database URL without the query parameters
ASYNC_DATABASE_URL = f"postgresql+asyncpg://{db_user}:{db_password}@{db_host}:{db_port}/{db_name}"

# Create an async SQLAlchemy engine with SSL configuration
engine = create_async_engine(
    ASYNC_DATABASE_URL,
    connect_args={"ssl": ssl_context},
    pool_size=5,
    max_overflow=10,
    pool_timeout=30,
    pool_recycle=1800,
    pool_pre_ping=True,
    echo=False
)

# Create a session factory for creating database sessions
async_session = sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False
)

# Create a base class for declarative models
Base = declarative_base()

# Dependency to get an async database session
async def get_db():
    async with async_session() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()
```

With the above code, we've set up the database connection and a dependency to get an async database session in our FastAPI application.

Now let's create our database models (`app/models.py`) which will represent the webhook events:

```python
# app/models.py
from sqlalchemy import Column, Integer, String, Boolean, DateTime, Text, JSON
from sqlalchemy.sql import func
from app.database import Base

class WebhookEvent(Base):
    __tablename__ = "webhook_events"

    id = Column(Integer, primary_key=True, index=True)
    event_type = Column(String, index=True)
    delivery_id = Column(String, unique=True, index=True)
    signature = Column(String)
    payload = Column(JSON)
    processed = Column(Boolean, default=False)
    created_at = Column(DateTime(timezone=True), server_default=func.now())

    def __repr__(self):
        return f"<WebhookEvent(id={self.id}, event_type='{self.event_type}')>"
```

This model represents a webhook event with the fields defined earlier. We'll use it to store webhook events in Postgres.

## Implement webhook endpoints

With the database models in place, implement the endpoint that receives and stores GitHub webhook events. Update `app/main.py`:

```python
# app/main.py
import json
import hmac
import hashlib
from fastapi import FastAPI, Request, Depends, Header, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.future import select
from app.database import get_db, engine, Base
from app.models import WebhookEvent
from app.config import settings

app = FastAPI(title="Webhook Receiver")

# Create database tables if they don't exist
@app.on_event("startup")
async def startup():
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)

@app.get("/")
async def root():
    return {"message": "Webhook Receiver is running"}

@app.get("/webhooks/events")
async def view_webhook_events(limit: int = 10, db: AsyncSession = Depends(get_db)):
    """View recent webhook events - useful for debugging."""
    result = await db.execute(select(WebhookEvent).order_by(WebhookEvent.created_at.desc()).limit(limit))
    events = result.scalars().all()
    return events

@app.post("/webhooks/github")
async def github_webhook(
    request: Request,
    x_github_event: str = Header(None),
    x_github_delivery: str = Header(None),
    x_hub_signature_256: str = Header(None),
    db: AsyncSession = Depends(get_db)
):
    # Read the request body
    body = await request.body()

    # Verify the webhook signature (we'll implement this next)
    is_valid = verify_signature(body, x_hub_signature_256)
    if not is_valid:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid signature"
        )

    # Parse the JSON payload
    try:
        payload = json.loads(body)
    except json.JSONDecodeError:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid JSON payload"
        )

    # Store the webhook event in the database
    webhook_event = WebhookEvent(
        event_type=x_github_event,
        delivery_id=x_github_delivery,
        signature=x_hub_signature_256,
        payload=payload,
        processed=False
    )

    db.add(webhook_event)
    await db.commit()
    await db.refresh(webhook_event)

    # Process the webhook event (we'll implement this later)
    await process_webhook_event(webhook_event.id, db)

    return {"status": "success", "event_id": webhook_event.id}

# Placeholder functions to be implemented
def verify_signature(body, signature):
    # We'll implement this next
    return True

async def process_webhook_event(event_id, db):
    # We'll implement this later
    pass
```

Here we are setting up a FastAPI application with a `/webhooks/github` endpoint to receive GitHub webhook events. The endpoint reads the request body, verifies the webhook signature, parses the JSON payload, stores the event in the database, and then processes it.

## Add webhook verification

GitHub signs each webhook so you can verify that it came from GitHub. Implement the signature verification function:

```python
def verify_signature(body, signature):
    if not signature:
        return False

    # The signature from GitHub starts with 'sha256='
    if not signature.startswith("sha256="):
        return False

    # Remove the 'sha256=' prefix
    signature = signature[7:]

    # Calculate the HMAC SHA256 signature using our webhook secret
    secret = settings.webhook_secret.encode()
    expected_signature = hmac.new(secret, body, hashlib.sha256).hexdigest()

    # Compare the calculated signature with the one from GitHub
    return hmac.compare_digest(expected_signature, signature)
```

Replace the placeholder `verify_signature` function with this implementation. This function verifies the webhook signature by calculating the HMAC SHA256 signature using the webhook secret and comparing it with the signature sent by GitHub.

## Process webhook events

Now, let's implement the `process_webhook_event` function to handle different types of GitHub webhook events:

```python
async def process_webhook_event(event_id, db):
    # Fetch the webhook event from the database
    result = await db.execute(select(WebhookEvent).where(WebhookEvent.id == event_id))
    event = result.scalars().first()

    if not event:
        return

    try:
        # Process different event types
        if event.event_type == "push":
            await process_push_event(event)
        elif event.event_type == "pull_request":
            await process_pull_request_event(event)
        elif event.event_type == "issues":
            await process_issue_event(event)
        # Add more event types as needed

        # Mark the event as processed
        event.processed = True
        await db.commit()

    except Exception as e:
        print(f"Error processing webhook event {event_id}: {e}")

async def process_push_event(event):
    """Process a GitHub push event."""
    payload = event.payload
    repo_name = payload.get("repository", {}).get("full_name")
    ref = payload.get("ref")
    commits = payload.get("commits", [])

    print(f"Push to {repo_name} on {ref} with {len(commits)} commits")
    # Handle the push event based on the commits

async def process_pull_request_event(event):
    """Process a GitHub pull request event."""
    payload = event.payload
    action = payload.get("action")
    pr_number = payload.get("number")
    repo_name = payload.get("repository", {}).get("full_name")

    print(f"Pull request #{pr_number} {action} in {repo_name}")
    # Handle the pull request based on the action (opened, closed, etc.)

async def process_issue_event(event):
    """Process a GitHub issue event."""
    payload = event.payload
    action = payload.get("action")
    issue_number = payload.get("issue", {}).get("number")
    repo_name = payload.get("repository", {}).get("full_name")

    print(f"Issue #{issue_number} {action} in {repo_name}")
    # Handle the issue based on the action (opened, closed, etc.)
```

In the `process_webhook_event` function, we fetch the webhook event from the database and process it based on the event type. We've provided placeholder functions for processing different types of GitHub webhook events, such as push events, pull request events, and issue events. You can extend these functions to handle other event types as needed.

## Test your webhook receiver

Now run the webhook receiver and test it with GitHub webhooks.

We will use ngrok to expose our local server to the internet so that GitHub can send webhook events to our FastAPI application. If you haven't installed ngrok yet, you can download it from [ngrok.com](https://ngrok.com/).

Once you have an account and ngrok installed, follow these steps to test your webhook receiver:

1. Start your FastAPI application:

```bash
uvicorn app.main:app --reload
```

2. Use ngrok to expose your local server to the internet:

```bash
ngrok http 8000
```

ngrok will provide you with a public URL (e.g., `https://abc123.ngrok.io`) that forwards to your local server. For testing, you can use this URL as the webhook endpoint. For production, deploy your FastAPI application to a server with a public domain and an SSL certificate.

3. If you don't have a GitHub repository to test with, create a new repository or use an existing one, and set up a webhook:
   - Go to your GitHub repository
   - Click on "Settings" > "Webhooks" > "Add webhook"
   - Set "Payload URL" to your ngrok URL + `/webhooks/github` (e.g., `https://abc123.ngrok.io/webhooks/github`)
   - Set "Content type" to `application/json`
   - Set "Secret" to the same value as your `WEBHOOK_SECRET` in the `.env` file
   - Choose which events you want to receive (e.g., "Just the push event")
   - Click "Add webhook"

4. Trigger an event in your repository:
   - Make a commit and push to the repository
   - Create or update an issue
   - Open a pull request

5. Monitor your FastAPI application logs to see the webhook events being received and processed.

Your FastAPI application should receive each webhook event, store it in your database, and process it based on the event type.

To view the stored webhook events, you can access the `/webhooks/events` endpoint. You should see the recent webhook events stored in the database returned as JSON.

The `/docs` endpoint of your FastAPI application shows the generated API documentation for your webhook endpoints.

## Security considerations

When implementing webhooks in a production environment, consider these security practices:

1. Validate signatures for every webhook provider, not only GitHub. Use a long random secret for signing the webhook payloads and keep it out of source control.

2. Always use HTTPS to encrypt webhook payloads in transit.

3. Protect your webhook endpoint from abuse by implementing rate limiting.

4. Set reasonable timeouts for webhook processing to prevent long-running tasks from blocking your application.

5. Make sure your webhook handling is idempotent, meaning the same webhook can be processed multiple times without causing problems (useful for retries).

6. Store the raw webhook payload initially, then process it asynchronously. This helps with debugging and retrying failed webhooks.

## Conclusion

You built a FastAPI application that verifies GitHub webhook signatures, stores events in a Neon database, and processes them by event type.

You can extend this webhook system to handle events from other services like Stripe (for payment notifications), Slack (for user interactions), or any other service that supports webhooks.

---

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