""" Flask-Limiter Extension """ from __future__ import annotations import dataclasses import datetime import itertools import logging import time import traceback import warnings import weakref from collections import defaultdict from functools import partial, wraps from types import TracebackType from typing import Type, overload import flask import flask.wrappers from limits.errors import ConfigurationError from limits.storage import MemoryStorage, Storage, storage_from_string from limits.strategies import STRATEGIES, RateLimiter from ordered_set import OrderedSet from werkzeug.http import http_date, parse_date from ._compat import request_context from .constants import MAX_BACKEND_CHECKS, ConfigVars, ExemptionScope, HeaderNames from .errors import RateLimitExceeded from .manager import LimitManager from .typing import ( Callable, Dict, List, Optional, P, R, Sequence, Set, Tuple, TypeVar, Union, cast, ) from .util import get_qualified_name from .wrappers import Limit, LimitGroup, RequestLimit @dataclasses.dataclass class LimiterContext: view_rate_limit: Optional[RequestLimit] = None view_rate_limits: List[RequestLimit] = dataclasses.field(default_factory=list) conditional_deductions: Dict[Limit, List[str]] = dataclasses.field( default_factory=dict ) seen_limits: OrderedSet[Limit] = dataclasses.field(default_factory=OrderedSet) def reset(self) -> None: self.view_rate_limit = None self.view_rate_limits.clear() self.conditional_deductions.clear() self.seen_limits.clear() class Limiter: """ The :class:`Limiter` class initializes the Flask-Limiter extension. :param key_func: a callable that returns the domain to rate limit by. :param app: :class:`flask.Flask` instance to initialize the extension with. :param default_limits: a variable list of strings or callables returning strings denoting default limits to apply to all routes that are not explicitely decorated with a limit. :ref:`ratelimit-string` for more details. :param default_limits_per_method: whether default limits are applied per method, per route or as a combination of all method per route. :param default_limits_exempt_when: a function that should return True/False to decide if the default limits should be skipped :param default_limits_deduct_when: a function that receives the current :class:`flask.Response` object and returns True/False to decide if a deduction should be made from the default rate limit(s) :param default_limits_cost: The cost of a hit to the default limits as an integer or a function that takes no parameters and returns an integer (Default: ``1``). :param application_limits: a variable list of strings or callables returning strings for limits that are applied to the entire application (i.e a shared limit for all routes) :param application_limits_per_method: whether application limits are applied per method, per route or as a combination of all method per route. :param application_limits_exempt_when: a function that should return True/False to decide if the application limits should be skipped :param application_limits_deduct_when: a function that receives the current :class:`flask.Response` object and returns True/False to decide if a deduction should be made from the application rate limit(s) :param application_limits_cost: The cost of a hit to the global application limits as an integer or a function that takes no parameters and returns an integer (Default: ``1``). :param headers_enabled: whether ``X-RateLimit`` response headers are written. :param header_name_mapping: Mapping of header names to use if :paramref:`Limiter.headers_enabled` is ``True``. If no mapping is provided the default values will be used. :param strategy: the strategy to use. Refer to :ref:`ratelimit-strategy` :param storage_uri: the storage location. Refer to :data:`RATELIMIT_STORAGE_URI` :param storage_options: kwargs to pass to the storage implementation upon instantiation. :param auto_check: whether to automatically check the rate limit in the before_request chain of the application. default ``True`` :param swallow_errors: whether to swallow any errors when hitting a rate limit. An exception will still be logged. default ``False`` :param fail_on_first_breach: whether to stop processing remaining limits after the first breach. default ``True`` :param on_breach: a function that will be called when any limit in this extension is breached. If the function returns an instance of :class:`flask.Response` that will be the response embedded into the :exc:`RateLimitExceeded` exception raised. :param meta_limits: a variable list of strings or callables returning strings for limits that are used to control the upper limit of a requesting client hitting any configured rate limit. Once a meta limit is exceeded all subsequent requests will raise a :class:`~flask_limiter.RateLimitExceeded` for the duration of the meta limit window. :param on_meta_breach: a function that will be called when a meta limit in this extension is breached. If the function returns an instance of :class:`flask.Response` that will be the response embedded into the :exc:`RateLimitExceeded` exception raised. :param in_memory_fallback: a variable list of strings or callables returning strings denoting fallback limits to apply when the storage is down. :param in_memory_fallback_enabled: fall back to in memory storage when the main storage is down and inherits the original limits. default ``False`` :param retry_after: Allows configuration of how the value of the `Retry-After` header is rendered. One of `http-date` or `delta-seconds`. :param key_prefix: prefix prepended to rate limiter keys and app context global names. :param request_identifier: a callable that returns the unique identity the current request. Defaults to :attr:`flask.Request.endpoint` :param enabled: Whether the extension is enabled or not """ def __init__( self, key_func: Callable[[], str], *, app: Optional[flask.Flask] = None, default_limits: Optional[List[Union[str, Callable[[], str]]]] = None, default_limits_per_method: Optional[bool] = None, default_limits_exempt_when: Optional[Callable[[], bool]] = None, default_limits_deduct_when: Optional[ Callable[[flask.wrappers.Response], bool] ] = None, default_limits_cost: Optional[Union[int, Callable[[], int]]] = None, application_limits: Optional[List[Union[str, Callable[[], str]]]] = None, application_limits_per_method: Optional[bool] = None, application_limits_exempt_when: Optional[Callable[[], bool]] = None, application_limits_deduct_when: Optional[ Callable[[flask.wrappers.Response], bool] ] = None, application_limits_cost: Optional[Union[int, Callable[[], int]]] = None, headers_enabled: Optional[bool] = None, header_name_mapping: Optional[Dict[HeaderNames, str]] = None, strategy: Optional[str] = None, storage_uri: Optional[str] = None, storage_options: Optional[Dict[str, Union[str, int]]] = None, auto_check: bool = True, swallow_errors: Optional[bool] = None, fail_on_first_breach: Optional[bool] = None, on_breach: Optional[ Callable[[RequestLimit], Optional[flask.wrappers.Response]] ] = None, meta_limits: Optional[List[Union[str, Callable[[], str]]]] = None, on_meta_breach: Optional[ Callable[[RequestLimit], Optional[flask.wrappers.Response]] ] = None, in_memory_fallback: Optional[List[str]] = None, in_memory_fallback_enabled: Optional[bool] = None, retry_after: Optional[str] = None, key_prefix: str = "", request_identifier: Optional[Callable[..., str]] = None, enabled: bool = True, ) -> None: self.app = app self.logger = logging.getLogger("flask-limiter") self.enabled = enabled self.initialized = False self._default_limits_per_method = default_limits_per_method self._default_limits_exempt_when = default_limits_exempt_when self._default_limits_deduct_when = default_limits_deduct_when self._default_limits_cost = default_limits_cost self._application_limits_per_method = application_limits_per_method self._application_limits_exempt_when = application_limits_exempt_when self._application_limits_deduct_when = application_limits_deduct_when self._application_limits_cost = application_limits_cost self._in_memory_fallback = [] self._in_memory_fallback_enabled = in_memory_fallback_enabled or ( in_memory_fallback and len(in_memory_fallback) > 0 ) self._route_exemptions: Dict[str, ExemptionScope] = {} self._blueprint_exemptions: Dict[str, ExemptionScope] = {} self._request_filters: List[Callable[[], bool]] = [] self._headers_enabled = headers_enabled self._header_mapping = header_name_mapping or {} self._retry_after = retry_after self._strategy = strategy self._storage_uri = storage_uri self._storage_options = storage_options or {} self._auto_check = auto_check self._swallow_errors = swallow_errors self._fail_on_first_breach = fail_on_first_breach self._on_breach = on_breach self._on_meta_breach = on_meta_breach self._key_func = key_func self._key_prefix = key_prefix self._request_identifier = request_identifier _default_limits = ( [ LimitGroup( limit_provider=limit, key_function=self._key_func, ) for limit in default_limits ] if default_limits else [] ) _application_limits = ( [ LimitGroup( limit_provider=limit, key_function=self._key_func, scope="global", shared=True, ) for limit in application_limits ] if application_limits else [] ) self._meta_limits = ( [ LimitGroup( limit_provider=limit, key_function=self._key_func, scope="meta", shared=True, ) for limit in meta_limits ] if meta_limits else [] ) if in_memory_fallback: for limit in in_memory_fallback: self._in_memory_fallback.append( LimitGroup( limit_provider=limit, key_function=self._key_func, ) ) self._storage: Optional[Storage] = None self._limiter: Optional[RateLimiter] = None self._storage_dead = False self._fallback_limiter: Optional[RateLimiter] = None self.__check_backend_count = 0 self.__last_check_backend = time.time() self._marked_for_limiting: Set[str] = set() self.logger.addHandler(logging.NullHandler()) self.limit_manager = LimitManager( application_limits=_application_limits, default_limits=_default_limits, decorated_limits={}, blueprint_limits={}, route_exemptions=self._route_exemptions, blueprint_exemptions=self._blueprint_exemptions, ) if app: self.init_app(app) def init_app(self, app: flask.Flask) -> None: """ :param app: :class:`flask.Flask` instance to rate limit. """ config = app.config self.enabled = config.setdefault(ConfigVars.ENABLED, self.enabled) if not self.enabled: return if self._default_limits_per_method is None: self._default_limits_per_method = bool( config.get(ConfigVars.DEFAULT_LIMITS_PER_METHOD, False) ) self._default_limits_exempt_when = ( self._default_limits_exempt_when or config.get(ConfigVars.DEFAULT_LIMITS_EXEMPT_WHEN) ) self._default_limits_deduct_when = ( self._default_limits_deduct_when or config.get(ConfigVars.DEFAULT_LIMITS_DEDUCT_WHEN) ) self._default_limits_cost = self._default_limits_cost or config.get( ConfigVars.DEFAULT_LIMITS_COST, 1 ) if self._swallow_errors is None: self._swallow_errors = bool(config.get(ConfigVars.SWALLOW_ERRORS, False)) if self._fail_on_first_breach is None: self._fail_on_first_breach = bool( config.get(ConfigVars.FAIL_ON_FIRST_BREACH, True) ) if self._headers_enabled is None: self._headers_enabled = bool(config.get(ConfigVars.HEADERS_ENABLED, False)) self._storage_options.update(config.get(ConfigVars.STORAGE_OPTIONS, {})) storage_uri_from_config = config.get(ConfigVars.STORAGE_URI, None) if not storage_uri_from_config: if not self._storage_uri: warnings.warn( "Using the in-memory storage for tracking rate limits as no storage " "was explicitly specified. This is not recommended for production use. " "See: https://flask-limiter.readthedocs.io#configuring-a-storage-backend " "for documentation about configuring the storage backend." ) storage_uri_from_config = "memory://" self._storage = cast( Storage, storage_from_string( self._storage_uri or storage_uri_from_config, **self._storage_options ), ) self._strategy = self._strategy or config.setdefault( ConfigVars.STRATEGY, "fixed-window" ) if self._strategy not in STRATEGIES: raise ConfigurationError( "Invalid rate limiting strategy %s" % self._strategy ) self._limiter = STRATEGIES[self._strategy](self._storage) self._header_mapping = { HeaderNames.RESET: self._header_mapping.get( HeaderNames.RESET, config.get(ConfigVars.HEADER_RESET, HeaderNames.RESET.value), ), HeaderNames.REMAINING: self._header_mapping.get( HeaderNames.REMAINING, config.get(ConfigVars.HEADER_REMAINING, HeaderNames.REMAINING.value), ), HeaderNames.LIMIT: self._header_mapping.get( HeaderNames.LIMIT, config.get(ConfigVars.HEADER_LIMIT, HeaderNames.LIMIT.value), ), HeaderNames.RETRY_AFTER: self._header_mapping.get( HeaderNames.RETRY_AFTER, config.get( ConfigVars.HEADER_RETRY_AFTER, HeaderNames.RETRY_AFTER.value ), ), } self._retry_after = self._retry_after or config.get( ConfigVars.HEADER_RETRY_AFTER_VALUE ) self._key_prefix = self._key_prefix or config.get(ConfigVars.KEY_PREFIX, "") self._request_identifier = self._request_identifier or config.get( ConfigVars.REQUEST_IDENTIFIER, lambda: flask.request.endpoint or "" ) app_limits = config.get(ConfigVars.APPLICATION_LIMITS, None) self._application_limits_cost = self._application_limits_cost or config.get( ConfigVars.APPLICATION_LIMITS_COST, 1 ) if self._application_limits_per_method is None: self._application_limits_per_method = bool( config.get(ConfigVars.APPLICATION_LIMITS_PER_METHOD, False) ) self._application_limits_exempt_when = ( self._application_limits_exempt_when or config.get(ConfigVars.APPLICATION_LIMITS_EXEMPT_WHEN) ) self._application_limits_deduct_when = ( self._application_limits_deduct_when or config.get(ConfigVars.APPLICATION_LIMITS_DEDUCT_WHEN) ) if not self.limit_manager._application_limits and app_limits: self.limit_manager.set_application_limits( [ LimitGroup( limit_provider=app_limits, key_function=self._key_func, scope="global", shared=True, per_method=self._application_limits_per_method, exempt_when=self._application_limits_exempt_when, deduct_when=self._application_limits_deduct_when, cost=self._application_limits_cost, ) ] ) else: app_limits = self.limit_manager._application_limits for group in app_limits: group.cost = self._application_limits_cost group.per_method = self._application_limits_per_method group.exempt_when = self._application_limits_exempt_when group.deduct_when = self._application_limits_deduct_when self.limit_manager.set_application_limits(app_limits) conf_limits = config.get(ConfigVars.DEFAULT_LIMITS, None) if not self.limit_manager._default_limits and conf_limits: self.limit_manager.set_default_limits( [ LimitGroup( limit_provider=conf_limits, key_function=self._key_func, per_method=self._default_limits_per_method, exempt_when=self._default_limits_exempt_when, deduct_when=self._default_limits_deduct_when, cost=self._default_limits_cost, ) ] ) else: default_limit_groups = self.limit_manager._default_limits for group in default_limit_groups: group.per_method = self._default_limits_per_method group.exempt_when = self._default_limits_exempt_when group.deduct_when = self._default_limits_deduct_when group.cost = self._default_limits_cost self.limit_manager.set_default_limits(default_limit_groups) meta_limits = config.get(ConfigVars.META_LIMITS, None) if not self._meta_limits and meta_limits: self._meta_limits = [ LimitGroup( limit_provider=meta_limits, key_function=self._key_func, scope="meta", shared=True, ) ] self._on_breach = self._on_breach or config.get(ConfigVars.ON_BREACH, None) self._on_meta_breach = self._on_meta_breach or config.get( ConfigVars.ON_META_BREACH, None ) self.__configure_fallbacks(app, self._strategy) if self not in app.extensions.setdefault("limiter", set()): if self._auto_check: app.before_request(self._check_request_limit) app.after_request(partial(Limiter.__inject_headers, self)) app.teardown_request(self.__release_context) app.extensions["limiter"].add(self) self.initialized = True @property def context(self) -> LimiterContext: """ The context is meant to exist for the lifetime of a request/response cycle per instance of the extension so as to keep track of any state used at different steps in the lifecycle (for example to pass information from the before request hook to the after_request hook) :meta private: """ ctx = request_context() if not hasattr(ctx, "_limiter_request_context"): ctx._limiter_request_context = defaultdict(LimiterContext) # type: ignore return cast( Dict[Limiter, LimiterContext], ctx._limiter_request_context, # type: ignore )[self] def limit( self, limit_value: Union[str, Callable[[], str]], *, key_func: Optional[Callable[[], str]] = None, per_method: bool = False, methods: Optional[List[str]] = None, error_message: Optional[str] = None, exempt_when: Optional[Callable[[], bool]] = None, override_defaults: bool = True, deduct_when: Optional[Callable[[flask.wrappers.Response], bool]] = None, on_breach: Optional[ Callable[[RequestLimit], Optional[flask.wrappers.Response]] ] = None, cost: Union[int, Callable[[], int]] = 1, scope: Optional[Union[str, Callable[[str], str]]] = None, ) -> LimitDecorator: """ Decorator to be used for rate limiting individual routes or blueprints. :param limit_value: rate limit string or a callable that returns a string. :ref:`ratelimit-string` for more details. :param key_func: function/lambda to extract the unique identifier for the rate limit. defaults to remote address of the request. :param per_method: whether the limit is sub categorized into the http method of the request. :param methods: if specified, only the methods in this list will be rate limited (default: ``None``). :param error_message: string (or callable that returns one) to override the error message used in the response. :param exempt_when: function/lambda used to decide if the rate limit should skipped. :param override_defaults: whether the decorated limit overrides the default limits (Default: ``True``). .. note:: When used with a :class:`~flask.Blueprint` the meaning of the parameter extends to any parents the blueprint instance is registered under. For more details see :ref:`recipes:nested blueprints` :param deduct_when: a function that receives the current :class:`flask.Response` object and returns True/False to decide if a deduction should be done from the rate limit :param on_breach: a function that will be called when this limit is breached. If the function returns an instance of :class:`flask.Response` that will be the response embedded into the :exc:`RateLimitExceeded` exception raised. :param cost: The cost of a hit or a function that takes no parameters and returns the cost as an integer (Default: ``1``). :param scope: a string or callable that returns a string for further categorizing the rate limiting scope. This scope is combined with the current endpoint of the request. Changes - .. versionadded:: 2.9.0 The returned object can also be used as a context manager for rate limiting a code block inside a view. For example:: @app.route("/") def route(): try: with limiter.limit("10/second"): # something expensive except RateLimitExceeded: pass """ return LimitDecorator( self, limit_value, key_func, False, scope, per_method=per_method, methods=methods, error_message=error_message, exempt_when=exempt_when, override_defaults=override_defaults, deduct_when=deduct_when, on_breach=on_breach, cost=cost, ) def shared_limit( self, limit_value: Union[str, Callable[[], str]], scope: Union[str, Callable[[str], str]], *, key_func: Optional[Callable[[], str]] = None, per_method: bool = False, methods: Optional[List[str]] = None, error_message: Optional[str] = None, exempt_when: Optional[Callable[[], bool]] = None, override_defaults: bool = True, deduct_when: Optional[Callable[[flask.wrappers.Response], bool]] = None, on_breach: Optional[ Callable[[RequestLimit], Optional[flask.wrappers.Response]] ] = None, cost: Union[int, Callable[[], int]] = 1, ) -> LimitDecorator: """ decorator to be applied to multiple routes sharing the same rate limit. :param limit_value: rate limit string or a callable that returns a string. :ref:`ratelimit-string` for more details. :param scope: a string or callable that returns a string for defining the rate limiting scope. :param key_func: function/lambda to extract the unique identifier for the rate limit. defaults to remote address of the request. :param per_method: whether the limit is sub categorized into the http method of the request. :param methods: if specified, only the methods in this list will be rate limited (default: ``None``). :param error_message: string (or callable that returns one) to override the error message used in the response. :param function exempt_when: function/lambda used to decide if the rate limit should skipped. :param override_defaults: whether the decorated limit overrides the default limits. (default: ``True``) .. note:: When used with a :class:`~flask.Blueprint` the meaning of the parameter extends to any parents the blueprint instance is registered under. For more details see :ref:`recipes:nested blueprints` :param deduct_when: a function that receives the current :class:`flask.Response` object and returns True/False to decide if a deduction should be done from the rate limit :param on_breach: a function that will be called when this limit is breached. If the function returns an instance of :class:`flask.Response` that will be the response embedded into the :exc:`RateLimitExceeded` exception raised. :param cost: The cost of a hit or a function that takes no parameters and returns the cost as an integer (default: ``1``). """ return LimitDecorator( self, limit_value, key_func, True, scope, per_method=per_method, methods=methods, error_message=error_message, exempt_when=exempt_when, override_defaults=override_defaults, deduct_when=deduct_when, on_breach=on_breach, cost=cost, ) @overload def exempt( self, obj: flask.Blueprint, *, flags: ExemptionScope = ExemptionScope.APPLICATION | ExemptionScope.DEFAULT | ExemptionScope.META, ) -> flask.Blueprint: ... @overload def exempt( self, obj: Callable[..., R], *, flags: ExemptionScope = ExemptionScope.APPLICATION | ExemptionScope.DEFAULT | ExemptionScope.META, ) -> Callable[..., R]: ... @overload def exempt( self, *, flags: ExemptionScope = ExemptionScope.APPLICATION | ExemptionScope.DEFAULT | ExemptionScope.META, ) -> Union[ Callable[[Callable[P, R]], Callable[P, R]], Callable[[flask.Blueprint], flask.Blueprint], ]: ... def exempt( self, obj: Optional[Union[Callable[..., R], flask.Blueprint]] = None, *, flags: ExemptionScope = ExemptionScope.APPLICATION | ExemptionScope.DEFAULT | ExemptionScope.META, ) -> Union[ Callable[..., R], flask.Blueprint, Callable[[Callable[P, R]], Callable[P, R]], Callable[[flask.Blueprint], flask.Blueprint], ]: """ Mark a view function or all views in a blueprint as exempt from rate limits. :param obj: view function or blueprint to mark as exempt. :param flags: Controls the scope of the exemption. By default application wide limits, defaults configured on the extension and meta limits are opted out of. Additional flags can be used to control the behavior when :paramref:`obj` is a Blueprint that is nested under another Blueprint or has other Blueprints nested under it (See :ref:`recipes:nested blueprints`) The method can be used either as a decorator without any arguments (the default flags will apply and the route will be exempt from default and application limits:: @app.route("...") @limiter.exempt def route(...): ... Specific exemption flags can be provided at decoration time:: @app.route("...") @limiter.exempt(flags=ExemptionScope.APPLICATION) def route(...): ... If an entire blueprint (i.e. all routes under it) are to be exempted the method can be called with the blueprint as the first parameter and any additional flags:: bp = Blueprint(...) limiter.exempt(bp) limiter.exempt( bp, flags=ExemptionScope.DEFAULT|ExemptionScope.APPLICATION|ExemptionScope.ANCESTORS ) """ if isinstance(obj, flask.Blueprint): self.limit_manager.add_blueprint_exemption(obj.name, flags) elif obj: self.limit_manager.add_route_exemption(get_qualified_name(obj), flags) else: _R = TypeVar("_R") _WO = TypeVar("_WO", Callable[..., _R], flask.Blueprint) def wrapper(obj: _WO) -> _WO: return self.exempt(obj, flags=flags) return wrapper return obj def request_filter(self, fn: Callable[[], bool]) -> Callable[[], bool]: """ decorator to mark a function as a filter to be executed to check if the request is exempt from rate limiting. :param fn: The function will be called before evaluating any rate limits to decide whether to perform rate limit or skip it. """ self._request_filters.append(fn) return fn def __configure_fallbacks(self, app: flask.Flask, strategy: str) -> None: config = app.config fallback_enabled = config.get(ConfigVars.IN_MEMORY_FALLBACK_ENABLED, False) fallback_limits = config.get(ConfigVars.IN_MEMORY_FALLBACK, None) if not self._in_memory_fallback and fallback_limits: self._in_memory_fallback = [ LimitGroup( limit_provider=fallback_limits, key_function=self._key_func, scope=None, per_method=False, cost=1, ) ] if not self._in_memory_fallback_enabled: self._in_memory_fallback_enabled = ( fallback_enabled or len(self._in_memory_fallback) > 0 ) if self._in_memory_fallback_enabled: self._fallback_storage = MemoryStorage() self._fallback_limiter = STRATEGIES[strategy](self._fallback_storage) def __should_check_backend(self) -> bool: if self.__check_backend_count > MAX_BACKEND_CHECKS: self.__check_backend_count = 0 if time.time() - self.__last_check_backend > pow(2, self.__check_backend_count): self.__last_check_backend = time.time() self.__check_backend_count += 1 return True return False def check(self) -> None: """ Explicitly check the limits for the current request. This is only relevant if the extension was initialized with :paramref:`~flask_limiter.Limiter.auto_check` set to ``False`` :raises: RateLimitExceeded """ self._check_request_limit(in_middleware=False) def reset(self) -> None: """ resets the storage if it supports being reset """ try: self.storage.reset() self.logger.info("Storage has been reset and all limits cleared") except NotImplementedError: self.logger.warning("This storage type does not support being reset") @property def storage(self) -> Storage: """ The backend storage configured for the rate limiter """ assert self._storage return self._storage @property def limiter(self) -> RateLimiter: """ Instance of the rate limiting strategy used for performing rate limiting. """ if self._storage_dead and self._in_memory_fallback_enabled: limiter = self._fallback_limiter else: limiter = self._limiter assert limiter return limiter @property def current_limit(self) -> Optional[RequestLimit]: """ Get details for the most relevant rate limit used in this request. In a scenario where multiple rate limits are active for a single request and none are breached, the rate limit which applies to the smallest time window will be returned. .. important:: The value of ``remaining`` in :class:`RequestLimit` is after deduction for the current request. For example:: @limit("1/second") @limit("60/minute") @limit("2/day") def route(...): ... - Request 1 at ``t=0`` (no breach): this will return the details for for ``1/second`` - Request 2 at ``t=1`` (no breach): it will still return the details for ``1/second`` - Request 3 at ``t=2`` (breach): it will return the details for ``2/day`` """ return self.context.view_rate_limit @property def current_limits(self) -> List[RequestLimit]: """ Get a list of all rate limits that were applicable and evaluated within the context of this request. The limits are returned in a sorted order by smallest window size first. """ return self.context.view_rate_limits def identify_request(self) -> str: """ Returns the identity of the request (by default this is the :attr:`flask.Request.endpoint` associated by the view function that is handling the request). The behavior can be customized by initializing the extension with a callable argument for :paramref:`~flask_limiter.Limiter.request_identifier`. """ if self.initialized and self.enabled: assert self._request_identifier return self._request_identifier() return "" def __check_conditional_deductions(self, response: flask.wrappers.Response) -> None: for lim, args in self.context.conditional_deductions.items(): if lim.deduct_when and lim.deduct_when(response): try: self.limiter.hit(lim.limit, *args, cost=lim.cost) except Exception as err: if self._swallow_errors: self.logger.exception( "Failed to deduct rate limit. Swallowing error" ) else: raise err def __inject_headers( self, response: flask.wrappers.Response ) -> flask.wrappers.Response: self.__check_conditional_deductions(response) header_limit = self.current_limit if ( self.enabled and self._headers_enabled and header_limit and self._header_mapping ): try: reset_at = header_limit.reset_at response.headers.add( self._header_mapping[HeaderNames.LIMIT], str(header_limit.limit.amount), ) response.headers.add( self._header_mapping[HeaderNames.REMAINING], str(header_limit.remaining), ) response.headers.add( self._header_mapping[HeaderNames.RESET], str(reset_at) ) # response may have an existing retry after existing_retry_after_header = response.headers.get("Retry-After") if existing_retry_after_header is not None: # might be in http-date format retry_after: Optional[Union[float, datetime.datetime]] = parse_date( existing_retry_after_header ) # parse_date failure returns None if retry_after is None: retry_after = time.time() + int(existing_retry_after_header) if isinstance(retry_after, datetime.datetime): retry_after = time.mktime(retry_after.timetuple()) reset_at = max(int(retry_after), reset_at) # set the header instead of using add response.headers.set( self._header_mapping[HeaderNames.RETRY_AFTER], str( http_date(reset_at) if self._retry_after == "http-date" else int(reset_at - time.time()) ), ) except Exception as e: # noqa: E722 if self._in_memory_fallback_enabled and not self._storage_dead: self.logger.warning( "Rate limit storage unreachable - falling back to" " in-memory storage" ) self._storage_dead = True response = self.__inject_headers(response) else: if self._swallow_errors: self.logger.exception( "Failed to update rate limit headers. " "Swallowing error" ) else: raise e return response def __check_all_limits_exempt( self, endpoint: Optional[str], ) -> bool: return bool( not endpoint or not (self.enabled and self.initialized) or endpoint.split(".")[-1] == "static" or any(fn() for fn in self._request_filters) ) def __filter_limits( self, endpoint: Optional[str], blueprint: Optional[str], callable_name: Optional[str], in_middleware: bool = False, ) -> List[Limit]: if callable_name: name = callable_name else: view_func = flask.current_app.view_functions.get(endpoint or "", None) name = get_qualified_name(view_func) if view_func else "" if self.__check_all_limits_exempt(endpoint): return [] marked_for_limiting = ( name in self._marked_for_limiting or self.limit_manager.has_hints(endpoint or "") ) fallback_limits = [] if self._storage_dead and self._fallback_limiter: if in_middleware and name in self._marked_for_limiting: pass else: if ( self.__should_check_backend() and self._storage and self._storage.check() ): self.logger.info("Rate limit storage recovered") self._storage_dead = False self.__check_backend_count = 0 else: fallback_limits = list(itertools.chain(*self._in_memory_fallback)) if fallback_limits: return fallback_limits defaults, decorated = self.limit_manager.resolve_limits( flask.current_app, endpoint, blueprint, name, in_middleware, marked_for_limiting, ) limits = OrderedSet(defaults) - self.context.seen_limits self.context.seen_limits.update(defaults) return list(limits) + list(decorated) def __evaluate_limits(self, endpoint: str, limits: List[Limit]) -> None: failed_limits: List[Tuple[Limit, List[str]]] = [] limit_for_header: Optional[RequestLimit] = None view_limits: List[RequestLimit] = [] meta_limits = list(itertools.chain(*self._meta_limits)) if not ( ExemptionScope.META & self.limit_manager.exemption_scope( flask.current_app, endpoint, flask.request.blueprint ) ): for lim in meta_limits: limit_key, scope = lim.key_func(), lim.scope_for(endpoint, None) args = [limit_key, scope] if not self.limiter.test(lim.limit, *args, cost=lim.cost): breached_meta_limit = RequestLimit( self, lim.limit, args, True, lim.shared ) self.context.view_rate_limit = breached_meta_limit self.context.view_rate_limits = [breached_meta_limit] meta_breach_response = None if self._on_meta_breach: try: cb_response = self._on_meta_breach(breached_meta_limit) if isinstance(cb_response, flask.wrappers.Response): meta_breach_response = cb_response except Exception as err: # noqa if self._swallow_errors: self.logger.exception( "on_meta_breach callback failed with error %s", err ) else: raise err raise RateLimitExceeded(lim, response=meta_breach_response) for lim in sorted(limits, key=lambda x: x.limit): if lim.is_exempt or lim.method_exempt: continue limit_scope = lim.scope_for(endpoint, flask.request.method) limit_key = lim.key_func() args = [limit_key, limit_scope] kwargs = {} if not all(args): self.logger.error( f"Skipping limit: {lim.limit}. Empty value found in parameters." ) continue if self._key_prefix: args = [self._key_prefix, *args] if lim.deduct_when: self.context.conditional_deductions[lim] = args method = self.limiter.test else: method = self.limiter.hit kwargs["cost"] = lim.cost request_limit = RequestLimit(self, lim.limit, args, False, lim.shared) view_limits.append(request_limit) if not method(lim.limit, *args, **kwargs): self.logger.info( "ratelimit %s (%s) exceeded at endpoint: %s", lim.limit, limit_key, limit_scope, ) failed_limits.append((lim, args)) view_limits[-1].breached = True limit_for_header = view_limits[-1] if self._fail_on_first_breach: break if not limit_for_header and view_limits: # Pick a non shared limit over a shared one if possible # when no rate limit has been hit. This should be the best hint # for the client. explicit = [limit for limit in view_limits if not limit.shared] limit_for_header = explicit[0] if explicit else view_limits[0] self.context.view_rate_limit = limit_for_header or None self.context.view_rate_limits = view_limits on_breach_response = None for limit in failed_limits: request_limit = RequestLimit( self, limit[0].limit, limit[1], True, limit[0].shared ) for cb in dict.fromkeys([self._on_breach, limit[0].on_breach]): if cb: try: cb_response = cb(request_limit) if isinstance(cb_response, flask.wrappers.Response): on_breach_response = cb_response except Exception as err: # noqa if self._swallow_errors: self.logger.exception( "on_breach callback failed with error %s", err ) else: raise err if failed_limits: for lim in meta_limits: limit_scope = lim.scope_for(endpoint, flask.request.method) limit_key = lim.key_func() args = [limit_key, limit_scope] self.limiter.hit(lim.limit, *args) raise RateLimitExceeded( sorted(failed_limits, key=lambda x: x[0].limit)[0][0], response=on_breach_response, ) def _check_request_limit( self, callable_name: Optional[str] = None, in_middleware: bool = True ) -> None: endpoint = self.identify_request() try: all_limits = self.__filter_limits( endpoint, flask.request.blueprint, callable_name, in_middleware, ) self.__evaluate_limits(endpoint, all_limits) except Exception as e: if isinstance(e, RateLimitExceeded): raise e if self._in_memory_fallback_enabled and not self._storage_dead: self.logger.warning( "Rate limit storage unreachable - falling back to" " in-memory storage" ) self._storage_dead = True self.context.seen_limits.clear() self._check_request_limit( callable_name=callable_name, in_middleware=in_middleware ) else: if self._swallow_errors: self.logger.exception("Failed to rate limit. Swallowing error") else: raise e def __release_context(self, _: Optional[BaseException] = None) -> None: self.context.reset() class LimitDecorator: """ Wrapper used by :meth:`~flask_limiter.Limiter.limit` and :meth:`~flask_limiter.Limiter.shared_limit` when wrapping view functions or blueprints. """ def __init__( self, limiter: Limiter, limit_value: Union[Callable[[], str], str], key_func: Optional[Callable[[], str]] = None, shared: bool = False, scope: Optional[Union[Callable[[str], str], str]] = None, per_method: bool = False, methods: Optional[Sequence[str]] = None, error_message: Optional[str] = None, exempt_when: Optional[Callable[[], bool]] = None, override_defaults: bool = True, deduct_when: Optional[Callable[[flask.wrappers.Response], bool]] = None, on_breach: Optional[ Callable[[RequestLimit], Optional[flask.wrappers.Response]] ] = None, cost: Union[Callable[[], int], int] = 1, ): self.limiter: weakref.ProxyType[Limiter] = weakref.proxy(limiter) self.limit_value = limit_value self.key_func = key_func or self.limiter._key_func self.scope = scope self.per_method = per_method self.methods = tuple(methods) if methods else None self.error_message = error_message self.exempt_when = exempt_when self.override_defaults = override_defaults self.deduct_when = deduct_when self.on_breach = on_breach self.cost = cost self.is_static = not callable(self.limit_value) self.shared = shared @property def limit_group(self) -> LimitGroup: return LimitGroup( limit_provider=self.limit_value, key_function=self.key_func, scope=self.scope, per_method=self.per_method, methods=self.methods, error_message=self.error_message, exempt_when=self.exempt_when, override_defaults=self.override_defaults, deduct_when=self.deduct_when, on_breach=self.on_breach, cost=self.cost, shared=self.shared, ) def __enter__(self) -> None: tb = traceback.extract_stack(limit=2) qualified_location = f"{tb[0].filename}:{tb[0].name}:{tb[0].lineno}" # TODO: if use as a context manager becomes interesting/valuable # a less hacky approach than using the traceback and piggy backing # on the limit manager's knowledge of decorated limits might be worth it. self.limiter.limit_manager.add_decorated_limit( qualified_location, self.limit_group, override=True ) self.limiter.limit_manager.add_endpoint_hint( self.limiter.identify_request(), qualified_location ) self.limiter._check_request_limit( in_middleware=False, callable_name=qualified_location ) def __exit__( self, exc_type: Optional[Type[BaseException]], exc_value: Optional[BaseException], traceback: Optional[TracebackType], ) -> None: ... @overload def __call__(self, obj: Callable[P, R]) -> Callable[P, R]: ... @overload def __call__(self, obj: flask.Blueprint) -> None: ... def __call__( self, obj: Union[Callable[P, R], flask.Blueprint] ) -> Optional[Callable[P, R]]: if isinstance(obj, flask.Blueprint): name = obj.name else: name = get_qualified_name(obj) if isinstance(obj, flask.Blueprint): self.limiter.limit_manager.add_blueprint_limit(name, self.limit_group) return None else: self.limiter._marked_for_limiting.add(name) self.limiter.limit_manager.add_decorated_limit(name, self.limit_group) @wraps(obj) def __inner(*a: P.args, **k: P.kwargs) -> R: if ( self.limiter._auto_check and not getattr(obj, "__wrapper-limiter-instance", None) == self.limiter ): identity = self.limiter.identify_request() if identity: view_func = flask.current_app.view_functions.get(identity, None) if view_func and not get_qualified_name(view_func) == name: self.limiter.limit_manager.add_endpoint_hint(identity, name) self.limiter._check_request_limit( in_middleware=False, callable_name=name ) return cast(R, flask.current_app.ensure_sync(obj)(*a, **k)) # mark this wrapper as wrapped by a decorator from the limiter # from which the decorator was created. This ensures that stacked # decorations only trigger rate limiting from the inner most # decorator from each limiter instance (the weird need for # keeping track of the instance is to handle cases where multiple # limiter extensions are registered on the same application). setattr(__inner, "__wrapper-limiter-instance", self.limiter) return __inner