# Webhooks

This guide explains how to handle webhooks effectively in your Upstash Workflow applications. We'll walk through:

- setting up webhook endpoints
- verifying webhook requests
- and processing webhook events

<Card
  title="GitHub Repository"
  icon="github"
  href="https://github.com/upstash/workflow-js/tree/main/examples/nextjs-webhook-stripe"
  horizontal
>
  You can find the project source code on GitHub.
</Card>

## Overview

Webhooks allow external services to notify your application when events occur. For example, you can use webhooks to receive notifications when a new order is placed in your e-commerce store, a new user signs up, or a new message is sent in your chat application.

Upstash Workflow provides a simple way to receive these events and trigger workflows based on the incoming data autonomously.

### Setting Up Webhook Endpoints

#### Basic Setup

To create a webhook endpoint, use the `serve` function from `@upstash/workflow`:

<CodeGroup>

```typescript TypeScript
import { serve } from "@upstash/workflow/nextjs";

export const { POST } = serve(
  async (context) => {
    // Your webhook handling logic here
  },
  {
    initialPayloadParser: (payload) => {
      return payload;
    },
  }
);
```

```python Python
from fastapi import FastAPI
from upstash_workflow.fastapi import Serve
from upstash_workflow import AsyncWorkflowContext

app = FastAPI()
serve = Serve(app)


def initial_payload_parser(payload):
    return payload


@serve.post("/api/example", initial_payload_parser=initial_payload_parser)
async def example(context: AsyncWorkflowContext[str]) -> None:
    # Your webhook handling logic here

```

</CodeGroup>

#### Request Validation

Always validate incoming webhook requests to ensure they're legitimate. This way, no one other than the original webhook source can trigger your workflow. Here's an example using Clerk webhooks with Svix:

<CodeGroup>
```typescript Validate and Parse in Workflow - TypeScript
export const { POST } = serve<string>(async (context) => {
	const payloadString = context.requestPayload;
	const headerPayload = context.headers;

    let event: WebhookEvent;
    try {
    	event = await validateRequest(payloadString, headerPayload);
    } catch {
    	return
    }

    // Next steps based on the event

})

```

```python Validate and Parse in Workflow - Python
async def validate_request(payload_string: str, header_payload: dict):
    # Validate the request
    pass


@serve.post("/api/example")
async def example(context: AsyncWorkflowContext[str]) -> None:
    payload_string = context.request_payload
    header_payload = context.headers

    try:
        event = await validate_request(payload_string, header_payload)
    except:
        return

    # Next steps based on the event

```

```typescript Validation Function - TypeScript
import { Webhook } from "svix";
import { WebhookEvent } from "@clerk/nextjs/server";

const webhookSecret = "YOUR_WEBHOOK_SECRET";

async function validateRequest(payloadString: string, headerPayload: Headers) {
  const svixHeaders = {
    "svix-id": headerPayload.get("svix-id") as string,
    "svix-timestamp": headerPayload.get("svix-timestamp") as string,
    "svix-signature": headerPayload.get("svix-signature") as string,
  };
  const wh = new Webhook(webhookSecret);
  return wh.verify(payloadString, svixHeaders) as WebhookEvent;
}
```

</CodeGroup>

### Handling Webhook events

Use the context.run method to process webhook events in discrete, trackable steps:

<CodeGroup>

```typescript TypeScript
export const { POST } = serve(async (context) => {
  // ... Parse and validate the incoming request

  const user = await context.run<false | UserPayload>(
    "handle-webhook-event",
    async () => {
      if (event.type === "user.created") {
        const { id: clerkUserId, email_addresses, first_name } = event.data;
        const primaryEmail = email_addresses.find(
          (email) => (email.id = event.data.primary_email_address_id)
        );

        if (!primaryEmail) {
          return false;
        }

        return {
          event: event.type,
          userId: clerkUserId,
          email: primaryEmail.email_address,
          firstName: first_name,
        } as UserPayload;
      }
      return false;
    }
  );
});
```

```python Python
@serve.post("/api/example")
async def example(context: AsyncWorkflowContext[str]) -> None:
    # ... Parse and validate the incoming request

    async def _handle_webhook_event():
        if event.type == "user.created":
            clerk_user_id = event.data["id"]
            email_addresses = event.data["email_addresses"]
            first_name = event.data["first_name"]

            primary_email = next(
                (
                    email
                    for email in email_addresses
                    if email.id == event.data["primary_email_address_id"]
                ),
                None,
            )

            if not primary_email:
                return False

            return {
                "event": event.type,
                "user_id": clerk_user_id,
                "email": primary_email["email_address"],
                "first_name": first_name,
            }

        return False

    user = await context.run("handle-webhook-event", _handle_webhook_event)

```

</CodeGroup>

After validating the webhook and extracting the initial user data, you'll often need to perform additional operations like creating customer records, sending welcome emails etc.

<CodeGroup>

```typescript TypeScript
export const { POST } = serve(async (context) => {
  // ... Previous validation and user data extraction

  if (!user) {
    return;
  }

  const customer = await context.run("create-stripe-customer", async () => {
    return await stripe.customers.create({
      email: user.email,
      name: `${user.firstName} ${user.lastName}`,
      metadata: {
        userId: user.userId,
      },
    });
  });

  /// ... Additional steps
});
```

```python Python
@serve.post("/api/example")
async def example(context: AsyncWorkflowContext[str]) -> None:
    # ... Previous validation and user data extraction

    if not user:
        return

    async def _create_stripe_customer():
        return await stripe.customers.create(
            email=user["email"],
            name=f"{user['first_name']} {user['last_name']}",
            metadata={"user_id": user["user_id"]},
        )

    customer = await context.run("create-stripe-customer", _create_stripe_customer)

    # ... Additional steps

```

</CodeGroup>

You're now ready to perform any operation in the following steps.