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"""
Prometheus metrics middleware for automatic HTTP request tracking.
This middleware automatically records metrics for all HTTP requests,
including duration, status codes, and error rates.
"""
import time
from typing import Callable
from fastapi import Request, Response
from starlette.middleware.base import BaseHTTPMiddleware
from src.core import get_logger
from src.infrastructure.observability.metrics import metrics_manager, BusinessMetrics
logger = get_logger(__name__)
class MetricsMiddleware(BaseHTTPMiddleware):
"""Middleware for automatic Prometheus metrics collection."""
def __init__(self, app):
"""Initialize metrics middleware."""
super().__init__(app)
self.logger = get_logger(__name__)
async def dispatch(self, request: Request, call_next: Callable) -> Response:
"""Process request with automatic metrics collection."""
start_time = time.time()
# Skip metrics endpoint to avoid recursion
if request.url.path == "/api/v1/observability/metrics":
return await call_next(request)
# Extract path template (FastAPI route) for grouping
path_template = self._get_path_template(request)
method = request.method
try:
# Process request
response = await call_next(request)
# Calculate duration
duration = time.time() - start_time
# Record metrics
self._record_request_metrics(
method=method,
path=path_template,
status_code=response.status_code,
duration=duration
)
return response
except Exception as exc:
# Calculate duration even for errors
duration = time.time() - start_time
# Record error metrics
self._record_request_metrics(
method=method,
path=path_template,
status_code=500, # Default error status
duration=duration,
error=True
)
# Re-raise the exception
raise exc
def _get_path_template(self, request: Request) -> str:
"""
Get the path template from FastAPI route.
This extracts the route pattern (e.g., /users/{user_id})
instead of the actual path (e.g., /users/123) to avoid
high cardinality in metrics.
"""
# Try to get route from request scope
if hasattr(request, "scope") and "route" in request.scope:
route = request.scope["route"]
if hasattr(route, "path"):
return route.path
# Fallback to actual path, but try to generalize it
path = request.url.path
# Common patterns to generalize
# Replace UUIDs
import re
path = re.sub(
r'[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}',
'{uuid}',
path,
flags=re.IGNORECASE
)
# Replace numeric IDs
path = re.sub(r'/\d+', '/{id}', path)
# Limit cardinality for unknown paths
if path.count('/') > 5:
path = '/unknown/deep/path'
return path
def _record_request_metrics(
self,
method: str,
path: str,
status_code: int,
duration: float,
error: bool = False
):
"""Record HTTP request metrics."""
# HTTP request duration histogram
metrics_manager.observe_histogram(
"cidadao_ai_request_duration_seconds",
duration,
labels={
"method": method.upper(),
"endpoint": path,
"status_code": str(status_code)
}
)
# HTTP request counter
metrics_manager.increment_counter(
"cidadao_ai_http_requests_total",
labels={
"method": method.upper(),
"endpoint": path,
"status_code": str(status_code),
"status": "error" if error or status_code >= 400 else "success"
}
)
# Error rate tracking
if error or status_code >= 400:
metrics_manager.increment_counter(
"cidadao_ai_http_errors_total",
labels={
"method": method.upper(),
"endpoint": path,
"status_code": str(status_code),
"error_type": self._get_error_type(status_code)
}
)
# Track slow requests
if duration > 5.0: # Requests taking more than 5 seconds
metrics_manager.increment_counter(
"cidadao_ai_slow_requests_total",
labels={
"method": method.upper(),
"endpoint": path,
"duration_bucket": self._get_duration_bucket(duration)
}
)
# Update concurrent requests gauge (simplified - in production use proper tracking)
active_requests = getattr(self, '_active_requests', 0)
metrics_manager.set_gauge(
"cidadao_ai_http_requests_in_progress",
active_requests,
labels={"method": method.upper()}
)
def _get_error_type(self, status_code: int) -> str:
"""Categorize error types based on status code."""
if 400 <= status_code < 500:
return "client_error"
elif 500 <= status_code < 600:
return "server_error"
else:
return "unknown_error"
def _get_duration_bucket(self, duration: float) -> str:
"""Categorize request duration into buckets."""
if duration < 1:
return "0-1s"
elif duration < 5:
return "1-5s"
elif duration < 10:
return "5-10s"
elif duration < 30:
return "10-30s"
else:
return "30s+"
def setup_http_metrics():
"""Setup HTTP-specific metrics if not already registered."""
# HTTP requests total counter
try:
from src.infrastructure.observability.metrics import MetricConfig, MetricType
metrics_manager.register_metric(
MetricConfig(
name="cidadao_ai_http_requests_total",
description="Total HTTP requests received",
labels=["method", "endpoint", "status_code", "status"]
),
MetricType.COUNTER
)
metrics_manager.register_metric(
MetricConfig(
name="cidadao_ai_http_errors_total",
description="Total HTTP errors",
labels=["method", "endpoint", "status_code", "error_type"]
),
MetricType.COUNTER
)
metrics_manager.register_metric(
MetricConfig(
name="cidadao_ai_slow_requests_total",
description="Total slow HTTP requests",
labels=["method", "endpoint", "duration_bucket"]
),
MetricType.COUNTER
)
metrics_manager.register_metric(
MetricConfig(
name="cidadao_ai_http_requests_in_progress",
description="HTTP requests currently being processed",
labels=["method"]
),
MetricType.GAUGE
)
logger.info("HTTP metrics initialized")
except Exception as e:
logger.warning(f"Some HTTP metrics may already be registered: {e}") |