Decorators

drf-commons provides a suite of function/method decorators for logging, performance monitoring, query analysis, and cache debugging.

from drf_commons.decorators import (
    api_request_logger,
    log_function_call,
    log_exceptions,
    log_db_query,
    api_performance_monitor,
    cache_debug,
)

api_request_logger

Logs incoming API requests and outgoing responses with configurable field redaction.

@api_request_logger(
    log_body: bool = True,
    log_headers: bool = False,
    redact_fields: list = None,     # Additional fields to redact
    max_body_length: int = 1000,    # Truncate body beyond this length
)

Default redacted fields (always sanitized regardless of configuration):

• Authorization headers

• password, token, api_key, secret, access_token

Usage:

from drf_commons.decorators import api_request_logger
from rest_framework.views import APIView

class PaymentView(APIView):
    @api_request_logger(log_body=True, log_headers=False, redact_fields=["card_number"])
    def post(self, request):
        ...

Log output example:

{
  "event": "api_request",
  "method": "POST",
  "path": "/api/payments/",
  "user": "john@example.com",
  "body": {"amount": "99.99", "card_number": "[REDACTED]"},
  "duration_ms": 145.3,
  "status_code": 201
}

log_function_call

Logs function invocations with timing information and optional argument/result capture.

@log_function_call(
    logger_name: str = "drf_commons",
    log_args: bool = False,
    log_result: bool = False,
    category: str = None,
)

Usage:

from drf_commons.decorators import log_function_call

@log_function_call(
    logger_name="billing",
    log_args=True,
    log_result=True,
    category="BILLING",
)
def calculate_invoice_total(invoice_id: int, apply_discount: bool = False):
    ...

Log output (on call):

{
  "event": "function_call",
  "function": "calculate_invoice_total",
  "args": {"invoice_id": 42, "apply_discount": false},
  "duration_ms": 23.1,
  "result": {"total": "149.99", "currency": "USD"}
}

log_exceptions

Logs exceptions raised within a function. Optionally suppresses re-raising.

@log_exceptions(
    logger_name: str = "drf_commons",
    reraise: bool = True,
)

Usage:

from drf_commons.decorators import log_exceptions

@log_exceptions(logger_name="payments", reraise=True)
def charge_card(amount, card_token):
    # Exceptions logged with full context and re-raised
    ...

@log_exceptions(logger_name="notifications", reraise=False)
def send_welcome_email(user_id):
    # Exceptions logged but suppressed; function returns None on failure
    ...

log_db_query

Monitors database queries executed during function execution. Logs query count, individual queries, and execution time.

@log_db_query(query_type: str = "unknown")

Usage:

from drf_commons.decorators import log_db_query

@log_db_query(query_type="read")
def get_dashboard_data(user_id: int):
    articles = Article.objects.filter(created_by_id=user_id).count()
    comments = Comment.objects.filter(author_id=user_id).count()
    return {"articles": articles, "comments": comments}

Log output:

{
  "event": "db_query",
  "function": "get_dashboard_data",
  "query_type": "read",
  "query_count": 2,
  "duration_ms": 12.4,
  "queries": [
    {"sql": "SELECT COUNT(*) FROM articles WHERE ...", "duration_ms": 6.1},
    {"sql": "SELECT COUNT(*) FROM comments WHERE ...", "duration_ms": 5.2}
  ]
}

api_performance_monitor

Monitors API endpoint performance. Tracks request/response timing and logs a warning when execution exceeds the configured threshold.

@api_performance_monitor()

Usage:

from drf_commons.decorators import api_performance_monitor

class HeavyReportView(APIView):
    @api_performance_monitor()
    def get(self, request):
        ...

The threshold is read from COMMON["DEBUG_SLOW_REQUEST_THRESHOLD"] (default: 1.0 seconds).

cache_debug

Logs cache operations (get, set, delete) with timing information.

@cache_debug(cache_key_func: callable = None)

Usage:

from drf_commons.decorators import cache_debug
from django.core.cache import cache

@cache_debug(cache_key_func=lambda args, kwargs: f"user:{args[0]}")
def get_user_permissions(user_id: int):
    key = f"user:{user_id}:permissions"
    result = cache.get(key)
    if result is None:
        result = compute_permissions(user_id)
        cache.set(key, result, timeout=300)
    return result

Combining Decorators

Decorators compose naturally. Standard Python decorator stacking applies:

@api_request_logger(log_body=False)
@api_performance_monitor()
@log_db_query(query_type="read")
@log_exceptions(reraise=True)
def complex_view(request):
    ...

Execution order (outermost first): api_request_logger → api_performance_monitor → log_db_query → log_exceptions → function body.