> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agno.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Custom Middleware
> AgentOS with custom middleware for rate limiting, logging, and monitoring
This example demonstrates how to create and add custom middleware to your AgentOS application. We implement two common middleware types: rate limiting and request/response logging.
## Code
```python custom_middleware.py theme={null}
import time
from collections import defaultdict, deque
from typing import Dict
from agno.agent import Agent
from agno.db.postgres import PostgresDb
from agno.models.openai import OpenAIResponses
from agno.os import AgentOS
from agno.tools.hackernews import HackerNewsTools
from fastapi import Request, Response
from fastapi.responses import JSONResponse
from starlette.middleware.base import BaseHTTPMiddleware
# === Rate Limiting Middleware ===
class RateLimitMiddleware(BaseHTTPMiddleware):
"""
Rate limiting middleware that limits requests per IP address.
"""
def __init__(self, app, requests_per_minute: int = 60, window_size: int = 60):
super().__init__(app)
self.requests_per_minute = requests_per_minute
self.window_size = window_size
# Store request timestamps per IP
self.request_history: Dict[str, deque] = defaultdict(lambda: deque())
async def dispatch(self, request: Request, call_next) -> Response:
# Get client IP
client_ip = request.client.host if request.client else "unknown"
current_time = time.time()
# Clean old requests outside the window
history = self.request_history[client_ip]
while history and current_time - history[0] > self.window_size:
history.popleft()
# Check if rate limit exceeded
if len(history) >= self.requests_per_minute:
return JSONResponse(
status_code=429,
content={
"detail": f"Rate limit exceeded. Max {self.requests_per_minute} requests per minute."
},
)
# Add current request to history
history.append(current_time)
# Add rate limit headers
response = await call_next(request)
response.headers["X-RateLimit-Limit"] = str(self.requests_per_minute)
response.headers["X-RateLimit-Remaining"] = str(
self.requests_per_minute - len(history)
)
response.headers["X-RateLimit-Reset"] = str(
int(current_time + self.window_size)
)
return response
# === Request/Response Logging Middleware ===
class RequestLoggingMiddleware(BaseHTTPMiddleware):
"""
Request/response logging middleware with timing and basic info.
"""
def __init__(self, app, log_body: bool = False, log_headers: bool = False):
super().__init__(app)
self.log_body = log_body
self.log_headers = log_headers
self.request_count = 0
async def dispatch(self, request: Request, call_next) -> Response:
self.request_count += 1
start_time = time.time()
# Basic request info
client_ip = request.client.host if request.client else "unknown"
print(
f"🔍 Request #{self.request_count}: {request.method} {request.url.path} from {client_ip}"
)
# Optional: Log headers
if self.log_headers:
print(f"📋 Headers: {dict(request.headers)}")
# Optional: Log request body
if self.log_body and request.method in ["POST", "PUT", "PATCH"]:
body = await request.body()
if body:
print(f"📝 Body: {body.decode()}")
# Process request
response = await call_next(request)
# Log response info
duration = time.time() - start_time
status_emoji = "✅" if response.status_code < 400 else "❌"
print(
f"{status_emoji} Response: {response.status_code} in {duration * 1000:.1f}ms"
)
# Add request count to response header
response.headers["X-Request-Count"] = str(self.request_count)
return response
# === Setup database and agent ===
db = PostgresDb(db_url="postgresql+psycopg://ai:ai@localhost:5532/ai")
agent = Agent(
id="demo-agent",
name="Demo Agent",
model=OpenAIResponses(id="gpt-5.2"),
db=db,
tools=[HackerNewsTools()],
markdown=True,
)
agent_os = AgentOS(
description="Essential middleware demo with rate limiting and logging",
agents=[agent],
)
app = agent_os.get_app()
# Add custom middleware
app.add_middleware(
RateLimitMiddleware,
requests_per_minute=10,
window_size=60,
)
app.add_middleware(
RequestLoggingMiddleware,
log_body=False,
log_headers=False,
)
if __name__ == "__main__":
"""
Run the essential middleware demo using AgentOS serve method.
Features:
1. Rate Limiting (10 requests/minute)
2. Request/Response Logging
"""
agent_os.serve(
app="custom_middleware:app",
reload=True,
)
```
## Usage
```bash theme={null}
export OPENAI_API_KEY=your_openai_api_key
```
```bash theme={null}
uv pip install -U agno openai "fastapi[standard]" uvicorn sqlalchemy pgvector psycopg
```
```bash theme={null}
# Using Docker
docker run -d \
--name agno-postgres \
-e POSTGRES_DB=ai \
-e POSTGRES_USER=ai \
-e POSTGRES_PASSWORD=ai \
-p 5532:5432 \
pgvector/pgvector:pg17
```
```bash theme={null}
python custom_middleware.py
```
**Basic Request (observe console logging):**
```bash theme={null}
curl http://localhost:7777/config
```
**Test Rate Limiting (trigger 429 errors after 10 requests):**
```bash theme={null}
for i in {1..15}; do curl http://localhost:7777/config; done
```
**Check Rate Limit Headers:**
```bash theme={null}
curl -v http://localhost:7777/config
```
## Middleware Features
**Prevents API abuse by limiting requests per IP:**
* **Configurable Limits**: Set requests per minute and time window
* **Per-IP Tracking**: Different limits for different IP addresses
* **Sliding Window**: Uses a sliding time window for accurate limiting
* **Rate Limit Headers**: Provides client information about limits
**Headers Added:**
* `X-RateLimit-Limit`: Maximum requests allowed
* `X-RateLimit-Remaining`: Requests remaining in current window
* `X-RateLimit-Reset`: Timestamp when the window resets
**Customization:**
```python theme={null}
app.add_middleware(
RateLimitMiddleware,
requests_per_minute=100, # Allow 100 requests per minute
window_size=60, # 60-second sliding window
)
```
**Comprehensive request and response logging:**
* **Request Details**: Method, path, client IP, timing
* **Response Tracking**: Status codes, response time
* **Optional Body Logging**: Log request bodies for debugging
* **Optional Header Logging**: Log request headers
* **Request Counter**: Track total requests processed
**Console Output Example:**
```
🔍 Request #1: GET /config from 127.0.0.1
✅ Response: 200 in 45.2ms
🔍 Request #2: POST /agents/demo-agent/runs from 127.0.0.1
✅ Response: 200 in 1240.8ms
```
**Customization:**
```python theme={null}
app.add_middleware(
RequestLoggingMiddleware,
log_body=True, # Log request bodies
log_headers=True, # Log request headers
)
```
## Developer Resources
* [Custom Middleware Documentation](/agent-os/middleware/custom)
* [FastAPI Middleware Documentation](https://fastapi.tiangolo.com/tutorial/middleware/)