pyrate_limiter.abstracts package

class pyrate_limiter.abstracts.AbstractBucket

Bases: ABC

Base bucket interface Assumption: len(rates) always > 0 TODO: allow empty rates

close()

Release any resources held by the bucket.

Subclasses may override this method to perform any necessary cleanup (e.g., closing files, network connections, or releasing locks) when the bucket is no longer needed.

Return type:

None

abstractmethod count()

Count number of items in the bucket

Return type:

int | Awaitable[int]

failing_rate = None
abstractmethod flush()

Flush the whole bucket - Must remove failing-rate after flushing

Return type:

None | Awaitable[None]

is_async = None
abstractmethod leak(current_timestamp=None)

leaking bucket - removing items that are outdated

Return type:

int | Awaitable[int]

limiter_lock()

An additional lock to be used by Limiter in-front of the thread lock. Intended for multiprocessing environments where a thread lock is insufficient.

Return type:

object | None

now()

Retrieve current timestamp from the clock backend.

abstractmethod peek(index)

Peek at the rate-item at a specific index in latest-to-earliest order NOTE: The reason we cannot peek from the start of the queue(earliest-to-latest) is we can’t really tell how many outdated items are still in the queue

Return type:

RateItem | None | Awaitable[RateItem | None]

abstractmethod put(item)

Put an item (typically the current time) in the bucket return true if successful, otherwise false

Return type:

bool | Awaitable[bool]

put_decision(item)

put(), returning the full Decision rather than a bare bool.

Buckets need not override it; the default reads back what put() recorded. retry_after_ms is None for buckets that record none.

Return type:

Decision | Awaitable[Decision]

property rates
waiting(item)

Calculate time until bucket become availabe to consume an item again

Return type:

int | Awaitable[int]

class pyrate_limiter.abstracts.Algorithm

Bases: ABC

A rate-limiting policy, independent of any storage backend.

Implementations must be stateless so one instance can be shared across buckets and threads. The two sub-interfaces differ in what they need remembered per key: LogAlgorithm an entry per consumed unit, StateAlgorithm a fixed handful of numbers.

max_weight(rate)

Largest weight this policy can ever admit under rate.

Return type:

int

class pyrate_limiter.abstracts.BucketAsyncWrapper(bucket)

Bases: AbstractBucket

BucketAsyncWrapper is a wrapping over any bucket that turns a async/synchronous bucket into an async one

async count()

Count number of items in the bucket

property failing_rate

The type of the None singleton.

async flush()

Flush the whole bucket - Must remove failing-rate after flushing

Return type:

None

is_async = True
async leak(current_timestamp=None)

leaking bucket - removing items that are outdated

Return type:

int

now()

Retrieve current timestamp from the clock backend.

Return type:

int

async peek(index)

Peek at the rate-item at a specific index in latest-to-earliest order NOTE: The reason we cannot peek from the start of the queue(earliest-to-latest) is we can’t really tell how many outdated items are still in the queue

Return type:

RateItem | None

async put(item)

Put an item (typically the current time) in the bucket return true if successful, otherwise false

property rates
async waiting(item)

Calculate time until bucket become availabe to consume an item again

Return type:

int

class pyrate_limiter.abstracts.BucketFactory

Bases: ABC

Asbtract BucketFactory class. It is reserved for user to implement/override this class with his own bucket-routing/creating logic

close()
Return type:

None

create(bucket_class, *args, **kwargs)

Creating a bucket dynamically

Return type:

AbstractBucket

dispose(bucket)

Delete a bucket from the factory

Return type:

bool

abstractmethod get(item)

Get the corresponding bucket to this item

Return type:

AbstractBucket | Awaitable[AbstractBucket]

get_buckets()

Iterator over all buckets in the factory

Return type:

List[AbstractBucket]

property leak_interval

Retrieve leak-interval from inner Leaker task

schedule_leak(new_bucket)

Schedule all the buckets’ leak, reset bucket’s failing rate

Return type:

None

abstractmethod wrap_item(name, weight=1)

Add the current timestamp to the receiving item using any clock backend - Turn it into a RateItem - Can return either a coroutine or a RateItem instance

Return type:

RateItem | Awaitable[RateItem]

class pyrate_limiter.abstracts.Decision(failing_rate=None, retry_after_ms=None)

Bases: object

Outcome of an admit check.

retry_after_ms is measured from the checked item’s own timestamp. None means “unknown, ask AbstractBucket.waiting()” - either the weight can never fit, or the backend does not compute a wait. It does not mean “no wait”.

property allowed
failing_rate = None
retry_after_ms = None
class pyrate_limiter.abstracts.Duration(*values)

Bases: Enum

Interval helper class

DAY = 86400000
HOUR = 3600000
MINUTE = 60000
SECOND = 1000
WEEK = 604800000
static readable(value)
Return type:

str

class pyrate_limiter.abstracts.FixedWindow

Bases: LogAlgorithm

Counts within a wall-clock-aligned window that resets every interval.

Cheaper and coarser than the rolling window: up to 2 * limit can pass across a window boundary. Use it to mirror an upstream API that genuinely resets on the hour rather than rolling.

admit(rates, counts, weight)

Whether weight more units fit, given counts aligned to rates.

Return type:

Decision

retry_after(rate, now, blocking_timestamp)

Milliseconds until room exists under rate.

blocking_timestamp is the entry named by blocking_offset(), or None when there is none - or when the policy never asks for one.

Return type:

int

window_start(rate, now)

Inclusive lower bound of rate’s counting window at now.

Return type:

int

class pyrate_limiter.abstracts.GCRA

Bases: StateAlgorithm

Generic Cell Rate Algorithm - a leaky bucket kept as one timestamp.

Tracks a theoretical arrival time (TAT) per rate: the moment the bucket would next be empty. Admitting weight pushes the TAT forward by weight * emission_interval; the request is allowed while that stays within burst units of now.

Sustains limit per interval while tolerating a burst of rate.burst, using one number per rate instead of an entry per unit.

State is integer microseconds, not fractional milliseconds. An absolute TAT in epoch ms is ~1.7e12, and accumulating a fractional emission interval onto it loses the low bits - enough that the accumulated sum of burst emissions no longer equals burst * emission, and the last unit of a full burst gets rejected by a rounding error. Integers make it exact, and stay well inside the 2**53 a Lua double holds.

consumed(rates, state, now)

Units currently owed - the closest analogue to a log’s length.

Return type:

int

decode(values)

Parse persisted strings back into state.

Return type:

Tuple[float, ...]

initial(rates)

State for a key that has never been used.

Return type:

Tuple[float, ...]

max_weight(rate)

Largest weight this policy can ever admit under rate.

Return type:

int

redis_args(rates)

Arguments redis_script() needs, after the standard header.

The store passes these through without inspecting them, so a policy’s script and its arguments stay a matched pair that only the policy knows the shape of. The header the store supplies first is now, weight, ttl_ms, len(rates).

Return type:

List[int | float]

redis_script()

Lua implementing step() atomically, if this policy has one.

Return type:

str | None

step(rates, state, now, weight)

Apply an arrival of weight at now.

Returns the state to persist and the verdict. On denial it must return state unchanged: a rejected request spends nothing, under any rate.

Return type:

Tuple[Tuple[float, ...], Decision]

class pyrate_limiter.abstracts.LogAlgorithm

Bases: Algorithm

Policy over storage holding one timestamped entry per consumed unit.

abstractmethod admit(rates, counts, weight)

Whether weight more units fit, given counts aligned to rates.

Return type:

Decision

blocking_offset(rate, weight)

Offset from the newest stored entry (0-based) whose expiry makes room for weight, or None if the wait does not depend on an entry.

Return type:

int | None

decide(rates, counts, weight, now, peek_timestamp)

admit(), resolving the retry-after in the same step on denial.

peek_timestamp(offset) is only called when the policy asks for an entry and the item was rejected, so backends pay for the lookup only when it is needed.

Return type:

Decision

leak_bound(rates, now)

Timestamp below which an entry is outside every rate’s window.

Return type:

int

abstractmethod retry_after(rate, now, blocking_timestamp)

Milliseconds until room exists under rate.

blocking_timestamp is the entry named by blocking_offset(), or None when there is none - or when the policy never asks for one.

Return type:

int

abstractmethod window_start(rate, now)

Inclusive lower bound of rate’s counting window at now.

Return type:

int

class pyrate_limiter.abstracts.Rate(limit, interval, burst=None)

Bases: object

Rate definition.

Parameters:

  • limit (int) – Number of requests allowed within interval

  • interval (int | Duration) – Time interval, in miliseconds

  • burst (int | None) – How many units may be spent at once. Only the constant-state algorithms (GCRA, TokenBucket) read it; the window algorithms admit up to limit per window regardless. Defaults to limit, which is classic token-bucket behaviour - a full bucket at rest. burst=1 makes the output perfectly smooth.

burst
interval
limit
class pyrate_limiter.abstracts.RateItem(name, timestamp, weight=1)

Bases: object

RateItem is a wrapper for bucket to work with

name
timestamp
weight
class pyrate_limiter.abstracts.SlidingWindowLog

Bases: LogAlgorithm

Precise rolling window: admit while each rate’s last interval stays under its limit.

The default. Exact, at the cost of one stored entry per consumed unit.

admit(rates, counts, weight)

Whether weight more units fit, given counts aligned to rates.

Return type:

Decision

blocking_offset(rate, weight)

Offset from the newest stored entry (0-based) whose expiry makes room for weight, or None if the wait does not depend on an entry.

Return type:

int | None

retry_after(rate, now, blocking_timestamp)

Milliseconds until room exists under rate.

blocking_timestamp is the entry named by blocking_offset(), or None when there is none - or when the policy never asks for one.

Return type:

int

window_start(rate, now)

Inclusive lower bound of rate’s counting window at now.

Return type:

int

class pyrate_limiter.abstracts.StateAlgorithm

Bases: Algorithm

Policy whose state is a fixed-size tuple of numbers, not a log.

Storage keeps one small value per key however much traffic passes, and the wait comes out in closed form. In exchange the check is destructive - it spends what it admits - so step() must evaluate every rate before committing any of them.

consumed(rates, state, now)

Units currently owed - the closest analogue to a log’s length.

Return type:

int

decode(values)

Parse persisted strings back into state.

Return type:

Tuple[float, ...]

abstractmethod initial(rates)

State for a key that has never been used.

Return type:

Tuple[float, ...]

redis_args(rates)

Arguments redis_script() needs, after the standard header.

The store passes these through without inspecting them, so a policy’s script and its arguments stay a matched pair that only the policy knows the shape of. The header the store supplies first is now, weight, ttl_ms, len(rates).

Return type:

List[int | float]

redis_script()

Lua implementing step() atomically, if this policy has one.

Return type:

str | None

abstractmethod step(rates, state, now, weight)

Apply an arrival of weight at now.

Returns the state to persist and the verdict. On denial it must return state unchanged: a rejected request spends nothing, under any rate.

Return type:

Tuple[Tuple[float, ...], Decision]

class pyrate_limiter.abstracts.StateStore

Bases: ABC

Holds one key’s state for a StateAlgorithm.

The store’s only real job is atomicity: check() must read the state, apply the transition and persist the result without another writer interleaving. How it achieves that is its own business - a lock in-process, a Lua script in Redis.

abstractmethod check(algorithm, rates, now, weight)

Apply algorithm.step to the stored state, atomically.

Return type:

Decision | Awaitable[Decision]

close()

Release any resources held. Optional.

Return type:

None

default_clock = <pyrate_limiter.clocks.MonotonicClock object>

Used when the bucket is not given a clock. Shared stores override it, since a monotonic clock means nothing across machines.

is_async = False

None means “ask the Leaker to probe” (a client that may be either).

abstractmethod read(algorithm, rates)

Current state. For reporting only - never the basis of a decision.

Return type:

Tuple[float, ...] | Awaitable[Tuple[float, ...]]

abstractmethod reset()

Forget everything, as though the key had never been used.

Return type:

None | Awaitable[None]

class pyrate_limiter.abstracts.TokenBucket

Bases: GCRA

Token bucket, which is GCRA under a more familiar name.

A bucket of rate.burst tokens refilling at rate.limit / rate.interval admits exactly what GCRA does with an emission interval of interval / limit. Same implementation, one float of state rather than a token count plus a refill timestamp.

Submodules