import functools from time import perf_counter from asgiref.local import Local from django.conf import settings from django.core.cache import CacheHandler, caches from django.utils.translation import gettext_lazy as _, ngettext from debug_toolbar.panels import Panel from debug_toolbar.utils import get_stack_trace, get_template_info, render_stacktrace # The order of the methods in this list determines the order in which they are listed in # the Commands table in the panel content. WRAPPED_CACHE_METHODS = [ "add", "get", "set", "get_or_set", "touch", "delete", "clear", "get_many", "set_many", "delete_many", "has_key", "incr", "decr", "incr_version", "decr_version", ] def _monkey_patch_method(cache, name): original_method = getattr(cache, name) @functools.wraps(original_method) def wrapper(*args, **kwargs): panel = cache._djdt_panel if panel is None: return original_method(*args, **kwargs) else: return panel._record_call(cache, name, original_method, args, kwargs) setattr(cache, name, wrapper) def _monkey_patch_cache(cache): if not hasattr(cache, "_djdt_patched"): for name in WRAPPED_CACHE_METHODS: _monkey_patch_method(cache, name) cache._djdt_patched = True class CachePanel(Panel): """ Panel that displays the cache statistics. """ template = "debug_toolbar/panels/cache.html" _context_locals = Local() def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.total_time = 0 self.hits = 0 self.misses = 0 self.calls = [] self.counts = {name: 0 for name in WRAPPED_CACHE_METHODS} @classmethod def current_instance(cls): """ Return the currently enabled CachePanel instance or None. If a request is in process with a CachePanel enabled, this will return that panel (based on the current thread or async task). Otherwise it will return None. """ return getattr(cls._context_locals, "current_instance", None) @classmethod def ready(cls): if not hasattr(CacheHandler, "_djdt_patched"): # Wrap the CacheHander.create_connection() method to monkey patch any new # cache connections that are opened while instrumentation is enabled. In # the interests of thread safety, this is done once at startup time and # never removed. original_method = CacheHandler.create_connection @functools.wraps(original_method) def wrapper(self, alias): cache = original_method(self, alias) panel = cls.current_instance() if panel is not None: _monkey_patch_cache(cache) cache._djdt_panel = panel return cache CacheHandler.create_connection = wrapper CacheHandler._djdt_patched = True def _store_call_info( self, name, time_taken, return_value, args, kwargs, trace, template_info, backend, ): if name == "get" or name == "get_or_set": if return_value is None: self.misses += 1 else: self.hits += 1 elif name == "get_many": keys = kwargs["keys"] if "keys" in kwargs else args[0] self.hits += len(return_value) self.misses += len(keys) - len(return_value) time_taken *= 1000 self.total_time += time_taken self.counts[name] += 1 self.calls.append( { "time": time_taken, "name": name, "args": args, "kwargs": kwargs, "trace": render_stacktrace(trace), "template_info": template_info, "backend": backend, } ) def _record_call(self, cache, name, original_method, args, kwargs): # Some cache backends implement certain cache methods in terms of other cache # methods (e.g. get_or_set() in terms of get() and add()). In order to only # record the calls made directly by the user code, set the cache's _djdt_panel # attribute to None before invoking the original method, which will cause the # monkey-patched cache methods to skip recording additional calls made during # the course of this call, and then reset it back afterward. cache._djdt_panel = None try: start_time = perf_counter() value = original_method(*args, **kwargs) t = perf_counter() - start_time finally: cache._djdt_panel = self self._store_call_info( name=name, time_taken=t, return_value=value, args=args, kwargs=kwargs, trace=get_stack_trace(skip=2), template_info=get_template_info(), backend=cache, ) return value # Implement the Panel API nav_title = _("Cache") @property def nav_subtitle(self): cache_calls = len(self.calls) return ngettext( "%(cache_calls)d call in %(time).2fms", "%(cache_calls)d calls in %(time).2fms", cache_calls, ) % {"cache_calls": cache_calls, "time": self.total_time} @property def title(self): count = len(getattr(settings, "CACHES", ["default"])) return ngettext( "Cache calls from %(count)d backend", "Cache calls from %(count)d backends", count, ) % {"count": count} def enable_instrumentation(self): # Monkey patch all open cache connections. Django maintains cache connections # on a per-thread/async task basis, so this will not affect any concurrent # requests. The monkey patch of CacheHander.create_connection() installed in # the .ready() method will ensure that any new cache connections that get opened # during this request will also be monkey patched. for cache in caches.all(initialized_only=True): _monkey_patch_cache(cache) cache._djdt_panel = self # Mark this panel instance as the current one for the active thread/async task # context. This will be used by the CacheHander.create_connection() monkey # patch. self._context_locals.current_instance = self def disable_instrumentation(self): if hasattr(self._context_locals, "current_instance"): del self._context_locals.current_instance for cache in caches.all(initialized_only=True): cache._djdt_panel = None def generate_stats(self, request, response): self.record_stats( { "total_calls": len(self.calls), "calls": self.calls, "total_time": self.total_time, "hits": self.hits, "misses": self.misses, "counts": self.counts, } ) def generate_server_timing(self, request, response): stats = self.get_stats() value = stats.get("total_time", 0) title = "Cache {} Calls".format(stats.get("total_calls", 0)) self.record_server_timing("total_time", title, value)