django-fast-ratelimit 2.0.0

Fast ratelimit implementation with django caches

django-fast-ratelimit

Django-fast-ratelimit provides a secure and fast ratelimit facility based on the django caching framework. It uses a "Fixed window counter"-algorithm based on: https://medium.com/figma-design/an-alternative-approach-to-rate-limiting-f8a06cf7c94c

Installation

pip install django-fast-ratelimit

Note: pip >= 19 is required

usage

Decorator:

import ratelimit

@ratelimit.decorate(key="ip", rate="1/s")
def expensive_func(request):
    # how many ratelimits request limiting
    if request.ratelimit["request_limit"] > 0:
        # reschedule with end of rate epoch
        return request_waiting(request.ratelimit["end"])

or async

import ratelimit
import asyncio

@ratelimit.decorate(key="ip", rate="1/s")
async def expensive_func(request):
    # how many ratelimits request limiting
    if request.ratelimit["request_limit"] > 0:
        # reschedule with end of rate epoch
        await asyncio.sleep(request.ratelimit["end"])

blocking Decorator (raises RatelimitError):

import ratelimit

@ratelimit.decorate(key="ip", rate="1/s", block=True, decorate_name="ratelimit", methods=ratelimit.UNSAFE)
def expensive_func(request):
    # how many ratelimits request limiting
    if request.ratelimit["end"] > 0:

decorate View (requires group):

import ratelimit
from django.views.generic import View
from django.utils.decorators import method_decorator


@method_decorator(ratelimit.decorate(
  key="ip", rate="1/s", block=True, methods=ratelimit.SAFE, group="required"
), name="dispatch")
class FooView(View):
    ...

manual

import ratelimit


def func(request):
    ratelimit.get_ratelimit(key="ip", rate="1/s", request=request, group="123", action=ratelimit.Action.INCREASE)
    # or only for GET
    ratelimit.get_ratelimit(
        key="ip", rate="1/s", request=request, group="123", methods="GET", action=ratelimit.Action.INCREASE
    )
    # also simple calls possible (note: key in bytes format)
    ratelimit.get_ratelimit(
        key=b"abc", rate="1/s", group="123", action=ratelimit.Action.INCREASE
    )
    # retrieve ratelimit
    rlimit = ratelimit.get_ratelimit(
        key="ip", rate="1/s", request=request, group="123"
    )
    # reset (clears internal counter)
    counter_before_reset = rlimit.reset()
    # reset epoch (resets to the start of request/epoch)
    counter_before_reset = rlimit.reset(request)
    # decrease counter by arbitary amount
    rlimit.reset(19)
    # increase counter by arbitary amount
    rlimit.reset(-19)

    # check constraints of rate
    r = ratelimit.parse_rate("1/s")  # returns tuple (amount, period)
    assert(r[1]==1)  #  assert period is 1 second
    # for simple naming use o2g (object to group)
    ratelimit.get_ratelimit(
        key=b"abc", rate=r, group=ratelimit.o2g(func), action=ratelimit.Action.INCREASE
    )

manual async

import ratelimit


async def func(request):
    # retrieve ratelimit
    rlimit = await ratelimit.aget_ratelimit(
        key="ip", rate="1/s", request=request, group="123"
    )
    # reset (clears internal counter)
    await rlimit.areset()
    # reset epoch (resets to the start of request/epoch)
    await rlimit.areset(request)
    # decrease counter by arbitary amount
    await rlimit.areset(19)
    # increase counter by arbitary amount
    await rlimit.reset(-19)

parameters

ratelimit.get_ratelimit:

• group: group name, can be callable (fun(request))
• rate: rate limit, multiple modes Note: if count (first argument) is 0, then it raises the Disabled exception, the second argument must be greater then 0
  • str: default mode , specify rate in form of "1/4s" or "2/s" or "2/m"
  • 2 element tuple/list: first argument is amount, second are seconds
  • callable: can return of two
• methods: set of checked methods, can be callable (fun(request, group)), modes:
  • callable(request, group): allow dynamic
  • ratelimit.ALL (default): all methods are checked
  • ("HEAD", "GET"): list of checked methods
  • ratelimit.invertedset(["HEAD", "GET"]): inverted set of checked methods. Here: every method is checked, except HEAD, GET
• request: ingoing request (optional if key supports it and methods=ratelimit.ALL (default))
• key: multiple modes possible:
  • bool: True: skip key (should only be used for baking), False: disable cache (like RATELIMIT_ENABLE=False)
  • int: sidestep cache, value will be used for request_limit. 0 is for never blocking, >=1 blocks
  • str: "path.to.method:argument"
  • str: "inbuildmethod:argument" see methods for valid arguments
  • str: "inbuildmethod" method which is ready to use for (request, group)
  • tuple,list: ["method", args...]: method (can be also inbuild) with arbitary arguments
  • bytes: static key (supports mode without request)
  • callable: check return of function (fun(request, group)), return must be string (converted to bytes), bytes, bool or int (see "key" for effects)
• empty_to: convert empty keys (b"") to parameter. Must be bytes, bool or int (see "key" for effects) (default: keep b"")
• cache: specify cache to use, defaults to RATELIMIT_DEFAULT_CACHE setting (default: "default")
• hash_algo: name of hash algorithm for creating cache_key (defaults to RATELIMIT_KEY_HASH setting (default: "sha256")) Note: group is seperately hashed
• hashctx: optimation parameter, read the code and only use if you know what you are doing. It basically circumvents the parameter hashing and only hashes the key. If the key parameter is True even the key is skipped
• action {ratelimit.Action}:
  • PEEK: only lookup
  • INCREASE: count up and return result
  • RESET: return former result and reset
  • RESET_EPOCH: return count after reset of epoch. If neither epoch nor request is given like peek (default: {PEEK})
• epoch:
  • None: (default): use request as epoch
  • int: RESET_EPOCH resets by int. Negative int increases
  • object: attach counter to an open object (Note: it cannot be object() directly and neither an object with slots)

returns the dataclass Ratelimit

or raises ratelimit.Disabled in case of the count in the rate is zero

ratelimit.Ratelimit

Fields

• count: how often in the window the ip whatever was calling
• limit: limit when it should block
• request_limit: >=1 should block or reject, 0: should accept
• end: when does the block end
• group: group name
• group_key, cache: Optional, when specified reset and areset can be used, internal fields
• waited_ms: internal field, stores info how long was waited, in ms instead of rate seconds

Functions:

• can_reset: is a reset possible or were bypasses used
• reset: function to reset count if cache was used. When given an epoch the same as RESET_EPOCH
• areset: async version of reset
• check(block=False): raise RatelimitExceeded when block = True and ratelimit is exceeded
• acheck(wait=False, block=False): raise RatelimitExceeded when block = True and ratelimit is exceeded, wait for end of ratelimit duration when wait=True
• decorate_object(obj, name=None, block=False, replace=False): attach to object obj with name and use old limits too, pass block to check
• adecorate_object(obj, name=None, wait=False, block=False, replace=False): attach to object obj with name and use old limits too, pass block and wait to acheck

arguments: block: wait: replace:

ratelimit.aget_ratelimit:

same as get_ratelimit but supports async methods and has an optional parameter: wait, which suspends the execution (via asyncio.sleep) for the time specified in rate (second argument). This is only possible in async mode, as it would block too much in sync mode.

ratelimit.decorate:

All of ratelimit.get_ratelimit except request. group is here optional (except for decorations with method_decorator (no access to wrapped function)). Also supports:

• block: should hard block with an RatelimitExceeded exception (subclass of PermissionDenied) or only annotate request with ratelimit
• decorate_name: under what name the ratelimit is attached to the request. set to None/empty to not decorate request. Uses Ratelimit.decorate_object. Defaults to "ratelimit"
• wait (only async functions): suspends execution

Note: wait is tricky with method_decorator: you must ensure that the function decorated is async

helpers

ratelimit.invertedset:

inverts a collection, useful for http methods

ratelimit.get_RATELIMIT_TRUSTED_PROXY:

get the RATELIMIT_TRUSTED_PROXIES parsed as set note: this function is cached. If you change this setting while testing you may have to call:

ratelimit.get_RATELIMIT_TRUSTED_PROXY.cache_clear()

ratelimit.get_ip:

get client ip from request, using RATELIMIT_TRUSTED_PROXIES and forwarded headers

import ratelimit

ratelimit.get_ip(request)

ratelimit.o2g:

auto generate group names for method/function as input, see tests/test_decorators for more info

Example:

import ratelimit


class O2gView(View):
    def get(self, request, *args, **kwargs):
        request.ratelimit2 = ratelimit.get_ratelimit(
            group=ratelimit.o2g(self.get),
            rate="1/s",
            key=b"o2gtest",
            action=ratelimit.Action.INCREASE,
        )
        if request.ratelimit2.request_limit > 0:
            return HttpResponse(status=400)
        return HttpResponse()

methods

See in methods which methods are available. Here some of them:

• ip: use ip address as key, argument: [netmask ipv4/]netmask ipv6
• user: authenticated user primary key or b""
• user_or_ip: use autenticated user primary key as key. If not autenticated fallback to ip, also with netmask argument
• user_and_ip: same like user_or_ip except that the ip matching also applies for authenticated users
• get: generate key from multiple sources, input can be multiple input args or a dict with options

settings

• RATELIMIT_TESTCLIENT_FALLBACK: in case instead of a client ip a testclient is detected map to the fallback. Set to "invalid" to fail. Default ::1
• RATELIMIT_GROUP_HASH: hash function which is used for the group hash (default: md5)
• RATELIMIT_KEY_HASH: hash function which is used as default for the key hash, can be overridden with hash_algo (default: md5)
• RATELIMIT_ENABLE disable ratelimit (e.g. for tests) (default: enabled)
• RATELIMIT_KEY_PREFIX: internal prefix for the hash keys (so you don't have to create a new cache). Defaults to "frl:".
• RATELIMIT_DEFAULT_CACHE: default cache to use, defaults to "default" and can be overridden by cache parameter
• RATELIMIT_TRUSTED_PROXIES: "all" for allowing all ip addresses to provide forward informations, or an iterable with proxy ips (will be transformed to a set). Note there is a special ip: "unix" for unix sockets. Default: ["unix"] Used headers are: Forwarded, X-Forwarded-For

Update Notes:

in version 2.0.0 the parameter raise_on_limit was removed and replaced by check(block=True)

in version 1.0.0 the parameter include_reset was removed

in version 1.2.0 reset_epoch calls return the counter before reset instead of the count after

TODO:

• document and test wait parameter
• improve documentation decorate_name and decorate_object