Send Webhooks with FastAPI
This guide will show you how to send webhooks with FastAPI using Hookdeck's Outpost — an open-source event dispatcher. Outpost gives you a world-class webhook and event destination infrastructure in minutes for 1/10th the cost of alternatives.
Outpost supports Event Destinations, allowing you to deliver events to webhook endpoints, as well as to queues, and popular brokers or event gateways. These include AWS SQS, RabbitMQ, GCP Pub/Sub, Amazon EventBridge, Kafka, and more—all from a single platform.
The team behind it has drawn on their experience running Hookdeck Event Gateway and delivering over 100 billion events to thousands of customers.
Why use Outpost?
Sending webhooks can be trickier than you think. From managing fan‑out load, retries and backoff, to endpoint health management, and security/operational overhead. Outpost takes care of all of that so you only need to think about is how to send a webhook.
How to Send Webhooks with FastAPI + Outpost
Start by deploying an Outpost instance locally, via Docker, or deploy to production. For guidance, check out the Outpost quickstart or the GitHub repository.
FastAPI Support in Outpost
You can interact with Outpost using the Python SDK or the REST API. Each SDK provides a convenient way to interact with the Outpost API, including publishing events, managing topics, and configuring destinations.
pip install fastapi outpost_sdk uvicorn python-dotenv
Set Your Admin API Key
Before you can start making calls to the Outpost API you need to set an API key. The API uses bearer token authentication with a token of your choice configured through the API_KEY environment variable.
Create a .env file in your FastAPI project root:
ADMIN_API_KEY=<YOUR_BEARER_TOKEN_HERE>
OUTPOST_URL=http://localhost:3333
Send Webhooks (Publish Events)
In order to send a webhook, you have to instantiate Outpost, create a tenant, and create a destination for that tenant. Then you're ready to publish events to it.
Create an Outpost instance
with Outpost() as outpost
You can set the security parameters through the security optional parameter when initializing the SDK client instance. The selected scheme will be used by default to authenticate with the API for all operations that support it. For example:
with Outpost(
security=models.Security(
admin_api_key="<YOUR_BEARER_TOKEN_HERE>",
),
) as outpost
Create a new tenant.
A tenant in Outpost represents a user/team/organization in your product. Use the upsert() method to idempotently create or update a tenant: outpost.tenants.upsert()
Create a destination for that tenant.
The create() method is used to specify a new destination for the tenant. A destination is a specific instance of a destination type. For example, a webhook destination with a particular URL.
The request body structure depends on the destination type. Here we're creating a destination for a webhook, but it could be SQS, RabbitMQ, etc.
res = outpost.destinations.create(destination_create={
"tenant_id": tenant_id,
"id": user-provided-id,
"type": models.DestinationWebhook,
"topics": models.TopicsEnum.WILDCARD_,
"config": {
"url": "https://example.com/webhook-receiver",
},
})
Note that we specify topics. A topic is a way to categorize events and is a common concept found in Pub/Sub messaging.
Publish an event for the created tenant.
You can now use the publish() method to send an event to the specified topic, routed to a specific destination.
res = outpost.publish.event(data={
"user_id": "userid",
"status": "active",
}, id="evt_custom_123", tenant_id="<TENANT_ID>", destination_id="<DESTINATION_ID>", topic="topic.name", metadata={
"source": "crm",
})
id: Is optional but recommended. If left empty, it will be generated by hashing the topic, data, and timestamp.
tenant_id: The tenant ID to publish the event must match an existing tenant, otherwise it will be ignored.
destination_id: Optional. Used to force delivery to a specific destination regardless of the topic.
topic: Optional. Assumed to match ANY topic if left empty. If set, it must match one of the configured topics.
metadata: Arbitrary key-value mapping for event metadata.
data: The data JSON object will be sent as the webhook body. Now, every time you publish an event to this tenant, Outpost will send an HTTP POST request with the data payload to the destination URL.
Other fields:
eligible_for_retry: Optional, defaults to true. Controls whether an event should be automatically retried.
retries: Configuration to override the default retry behavior of the client.
Complete Example
Combining the examples above, you should end up with a FastAPI application that looks like the following:
First, create an Outpost service (services/outpost_client.py):
import os
from dotenv import load_dotenv
from outpost_sdk import Outpost, models
load_dotenv()
class OutpostService:
_instance = None
def __new__(cls):
if cls._instance is None:
cls._instance = super(OutpostService, cls).__new__(cls)
cls._instance._initialize()
return cls._instance
def _initialize(self):
admin_api_key = os.getenv("ADMIN_API_KEY")
server_url = os.getenv("OUTPOST_URL", "http://localhost:3333")
if not admin_api_key:
raise ValueError("Please set the ADMIN_API_KEY environment variable.")
self.client = Outpost(
security=models.Security(admin_api_key=admin_api_key),
server_url=f"{server_url}/api/v1",
)
def get_client(self):
return self.client
Then, create request/response models (models/webhook_models.py):
from typing import Optional, Dict, Any
from pydantic import BaseModel
class PublishEventRequest(BaseModel):
tenant_id: str
topic: str
data: Optional[Dict[str, Any]] = None
class WebhookReceiverRequest(BaseModel):
id: str
data: Dict[str, Any]
metadata: Optional[Dict[str, str]] = None
timestamp: str
class WebhookSetupResponse(BaseModel):
success: bool
message: str
data: Dict[str, Optional[str]]
class PublishEventResponse(BaseModel):
success: bool
message: str
event_id: Optional[str] = None
class PortalUrlResponse(BaseModel):
success: bool
portal_url: Optional[str] = None
Then, create API routes (routes/webhooks.py):
import uuid
import logging
from fastapi import APIRouter, HTTPException
from services.outpost_client import OutpostService
from models.webhook_models import (
PublishEventRequest,
PublishEventResponse,
WebhookReceiverRequest,
WebhookSetupResponse,
PortalUrlResponse,
)
router = APIRouter(prefix="/webhooks", tags=["webhooks"])
outpost_service = OutpostService()
outpost = outpost_service.get_client()
logger = logging.getLogger(__name__)
@router.post("/setup", response_model=WebhookSetupResponse)
async def setup_webhook():
"""
Create a new tenant and destination for webhook delivery.
"""
try:
tenant_id = f"tenant_{str(uuid.uuid4())}"
topic = "user.created"
destination_name = f"My Test Destination {str(uuid.uuid4())}"
# 1. Create a tenant
logger.info(f"Creating tenant: {tenant_id}")
tenant = outpost.tenants.upsert(tenant_id=tenant_id)
logger.info("Tenant created successfully")
# 2. Create a destination for the tenant
logger.info(f"Creating destination: {destination_name} for tenant {tenant_id}...")
destination = outpost.destinations.create(
tenant_id=tenant_id,
destination_create=models.DestinationCreateWebhook(
type=models.DestinationCreateWebhookType.WEBHOOK,
config=models.WebhookConfig(
url="https://example.com/webhook-receiver"
),
topics=[topic],
),
)
logger.info("Destination created successfully")
return WebhookSetupResponse(
success=True,
message="Tenant and destination created successfully",
data={
"tenant_id": tenant.id if hasattr(tenant, 'id') else tenant_id,
"destination_id": destination.id if hasattr(destination, 'id') else None,
},
)
except Exception as e:
logger.error(f"An error occurred: {e}")
raise HTTPException(status_code=500, detail=str(e))
@router.post("/publish", response_model=PublishEventResponse)
async def publish_event(payload: PublishEventRequest):
"""
Publish an event to a tenant's topic.
"""
try:
if not payload.tenant_id or not payload.topic:
raise HTTPException(
status_code=400,
detail="tenant_id and topic are required",
)
event_payload = payload.data or {
"user_id": "user_456",
"order_id": "order_xyz",
"timestamp": str(uuid.uuid4()),
}
logger.info(
f"Publishing event to topic {payload.topic} for tenant {payload.tenant_id}..."
)
event = outpost.publish.event(
data=event_payload,
tenant_id=payload.tenant_id,
topic=payload.topic,
eligible_for_retry=True,
)
logger.info("Event published successfully")
return PublishEventResponse(
success=True,
message="Event published successfully",
event_id=event.id if hasattr(event, 'id') else None,
)
except HTTPException:
raise
except Exception as e:
logger.error(f"An error occurred: {e}")
raise HTTPException(status_code=500, detail=str(e))
@router.post("/receiver")
async def webhook_receiver(payload: WebhookReceiverRequest):
"""
Receive and process incoming webhooks from Outpost.
"""
try:
logger.info(f"Webhook received: {payload}")
return {
"success": True,
"message": "Webhook received",
}
except Exception as e:
logger.error(f"An error occurred: {e}")
raise HTTPException(status_code=500, detail=str(e))
@router.get("/portal/{tenant_id}", response_model=PortalUrlResponse)
async def get_portal_url(tenant_id: str):
"""
Get the Tenant User Portal URL for a specific tenant.
"""
try:
if not tenant_id:
raise HTTPException(
status_code=400,
detail="tenant_id is required",
)
portal_url = outpost.tenants.get_portal_url(tenant_id=tenant_id)
return PortalUrlResponse(
success=True,
portal_url=portal_url.url if hasattr(portal_url, 'url') else None,
)
except HTTPException:
raise
except Exception as e:
logger.error(f"An error occurred: {e}")
raise HTTPException(status_code=500, detail=str(e))
Finally, create your main FastAPI application (main.py):
import logging
import os
from fastapi import FastAPI
from fastapi.responses import JSONResponse
from dotenv import load_dotenv
from routes.webhooks import router as webhooks_router
load_dotenv()
# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
# Create FastAPI app
app = FastAPI(
title="Outpost Webhooks API",
description="A FastAPI application for sending webhooks with Outpost",
version="1.0.0",
)
# Include routers
app.include_router(webhooks_router)
@app.get("/health")
async def health_check():
"""
Health check endpoint.
"""
return JSONResponse(
status_code=200,
content={"status": "ok"}
)
@app.get("/")
async def root():
"""
Root endpoint.
"""
return {
"message": "Welcome to Outpost Webhooks API",
"docs": "/docs",
"health": "/health",
}
if __name__ == "__main__":
import uvicorn
port = int(os.getenv("PORT", 8000))
uvicorn.run(app, host="0.0.0.0", port=port)
Create a requirements.txt file:
fastapi==0.104.1
uvicorn[standard]==0.24.0
outpost-sdk==1.0.0
python-dotenv==1.0.0
pydantic==2.4.0
Install dependencies and run:
pip install -r requirements.txt
python main.py
Or using uvicorn directly:
uvicorn main:app --reload
Expose Tenant User Portal
Your application can offer the user the option to configure their destination, view and retry their events using a themeable Tenant User Portal. Note that if the portal is used, then the Outpost API needs to be exposed to the public internet (or proxy requests to the Outpost API).
You can use get_portal_url() to return a redirect URL containing a JWT to authenticate the user with the portal. Then redirect your users to this URL or use it in an iframe in your FastAPI templates.
Build your own UI
While Outpost offers a user portal, you may want to build your own UI for users to manage their destinations and view their events. The portal is built using the Outpost API with JWT authentication. You can leverage the same API to build your own UI.
Help with debugging and testing webhooks
To help you and your users work with webhooks, we provide some additional tools. Like Hookdeck Console, a web-based inspector to test and debug incoming webhooks. As well as the Hookdeck CLI to forward webhook events to a local web server.
More information
That's everything you need to start sending webhooks with Outpost using FastAPI. For more information, please check out the Outpost documentation.
If you have any questions, we'd love to help. Please join the Hookdeck community on Slack.