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🔧 High-performance Python rate limiting library with multiple algorithms (Fixed Window, Sliding Window, Token Bucket, Leaky Bucket & GCRA) and storage backends (Redis, In-Memory).

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<h1 align="center">throttled-py</h1>

 🔧 High-performance Python rate limiting library with multiple algorithms (Fixed Window, Sliding Window, Token Bucket, Leaky Bucket & GCRA) and storage backends (Redis, In-Memory).

[简体中文](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/README_ZH.md) | English

[🔰 Installation](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-installation) | [🎨 Quick Start](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-quick-start) | [📝 Usage](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-usage) | [⚙️ Data Models](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#%EF%B8%8F-data-models--configuration) | [📊 Benchmarks](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-benchmarks) | [🍃 Inspiration](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-inspiration) | [📚 Version History](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-version-history) | [📄 License](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-license)

## ✨ Features

* Supports both synchronous and [asynchronous](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#3-asynchronous) (`async / await`).
* Provides thread-safe storage backends: [Redis(Standalone/Sentinel/Cluster)](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#redis), [In-Memory (with support for key expiration and eviction)](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#in-memory).
* Supports multiple rate limiting algorithms: [Fixed Window](https://github.com/ZhuoZhuoCrayon/throttled-py/tree/main/docs/basic#21-%E5%9B%BA%E5%AE%9A%E7%AA%97%E5%8F%A3%E8%AE%A1%E6%95%B0%E5%99%A8), [Sliding Window](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#22-%E6%BB%91%E5%8A%A8%E7%AA%97%E5%8F%A3), [Token Bucket](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#23-%E4%BB%A4%E7%89%8C%E6%A1%B6), [Leaky Bucket](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#24-%E6%BC%8F%E6%A1%B6) & [Generic Cell Rate Algorithm (GCRA)](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#25-gcra).
* Supports [configuration of rate limiting algorithms](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#3-algorithms) and provides flexible [quota configuration](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#4-quota-configuration).
* Supports immediate response and [wait-retry](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#wait--retry) modes, and provides [function call](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#function-call), [decorator](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#decorator), and [context manager](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#context-manager) modes.
* Supports integration with the [MCP](https://modelcontextprotocol.io/introduction) [Python SDK](https://github.com/modelcontextprotocol/python-sdk) to provide rate limiting support for model dialog processes.
* Official [FastAPI integration](https://throttled-py.readthedocs.io/en/latest/contrib/fastapi.html) with async decorator-based rate limiting, IETF-compliant `RateLimit-*` headers, and HTTP 429 handling.
* Excellent performance,  The execution time for a single rate limiting API call is equivalent to(see [Benchmarks](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#-benchmarks) for details):
  * In-Memory: ~2.5-4.5x `dict[key] += 1` operations.
  * Redis: ~1.06-1.37x `INCRBY key increment` operations.

## 🔰 Installation

```shell
$ pip install throttled-py
```

> Note: `v3.x` requires Python `>=3.10`. If you are using Python `3.8/3.9`, install `throttled-py<3.0.0`.

### 1) Optional Dependencies

Starting from [v2.0.0](https://github.com/ZhuoZhuoCrayon/throttled-py/releases/tag/v2.0.0), only core dependencies are installed by default.

To enable additional features, install optional dependencies as follows (multiple extras can be comma-separated):

```shell
$ pip install "throttled-py[redis]"

$ pip install "throttled-py[otel]"

$ pip install "throttled-py[redis,otel]"
```

| Extra       | Description                       |
|-------------|-----------------------------------|
| `memory`    | In-Memory backend is available by default (`memory` extra installs no additional dependencies). |
| `redis`     | Use Redis as storage backend.     |
| `otel`      | Enable OpenTelemetry hook support. |
| `fastapi`   | [FastAPI integration](https://throttled-py.readthedocs.io/en/latest/contrib/fastapi.html) with decorator-based rate limiting. |

## 🎨 Quick Start

### 1) Core API

* `limit`: Deduct requests and return [**RateLimitResult**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#1-ratelimitresult).
* `peek`: Check current rate limit state for a key (returns [**RateLimitState**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#2-ratelimitstate)).

### 2) Example

```python
from throttled import RateLimiterType, Throttled, utils

throttle = Throttled(
    # 📈 Use Token Bucket algorithm
    using=RateLimiterType.TOKEN_BUCKET.value,
    # 🪣 Set quota: 1,000 tokens per second (limit), bucket size 1,000 (burst)
    quota="1000/s burst 1000",
    # 📁 By default, global MemoryStore is used as the storage backend.
)

def call_api() -> bool:
    # 💧 Deduct 1 token for key="/ping"
    result = throttle.limit("/ping", cost=1)
    return result.limited

if __name__ == "__main__":
    # 💻 Python 3.12.10, Linux 5.4.119-1-tlinux4-0009.1, Arch: x86_64, Specs: 2C4G.
    # ✅ Total: 100000, 🕒 Latency: 0.0068 ms/op, 🚀 Throughput: 122513 req/s (--)
    # ❌ Denied: 98000 requests
    benchmark: utils.Benchmark = utils.Benchmark()
    denied_num: int = sum(benchmark.serial(call_api, 100_000))
    print(f"❌ Denied: {denied_num} requests")
```

### 3) Asynchronous

The core API is the same for synchronous and asynchronous code. Just replace `from throttled import ...` with `from throttled.asyncio import ...` in your code.

For example, rewrite `2) Example` to asynchronous:

```python
import asyncio
from throttled.asyncio import RateLimiterType, Throttled, utils

throttle = Throttled(
    using=RateLimiterType.TOKEN_BUCKET.value,
    quota="1000/s burst 1000",
)

async def call_api() -> bool:
    result = await throttle.limit("/ping", cost=1)
    return result.limited

async def main():
    benchmark: utils.Benchmark = utils.Benchmark()
    denied_num: int = sum(await benchmark.async_serial(call_api, 100_000))
    print(f"❌ Denied: {denied_num} requests")

if __name__ == "__main__":
    asyncio.run(main())
```

## 📝 Usage

### 1) Basic Usage

#### Function Call

```python
from throttled import Throttled

# Default: In-Memory storage, Token Bucket algorithm, 60 reqs / min.
throttle = Throttled()

# Deduct 1 request -> RateLimitResult(limited=False,
# state=RateLimitState(limit=60, remaining=59, reset_after=1, retry_after=0))
print(throttle.limit("key", 1))
# Check state -> RateLimitState(limit=60, remaining=59, reset_after=1, retry_after=0)
print(throttle.peek("key"))

# Deduct 60 requests (limited) -> RateLimitResult(limited=True,
# state=RateLimitState(limit=60, remaining=59, reset_after=1, retry_after=60))
print(throttle.limit("key", 60))
```

#### Decorator

```python
from throttled import Throttled, exceptions

@Throttled(key="/ping", quota="1/m")
def ping() -> str:
    return "ping"

ping()

try:
    ping()  # Raises LimitedError
except exceptions.LimitedError as exc:
    print(exc)  # Rate limit exceeded: remaining=0, reset_after=60, retry_after=60
```

#### Context Manager

You can use the context manager to limit the code block. When access is allowed, return [**RateLimitResult**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#1-ratelimitresult).

If the limit is exceeded or the retry timeout is exceeded, it will raise [**LimitedError**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#limitederror).

```python
from throttled import Throttled, exceptions

def call_api():
    print("doing something...")

throttle: Throttled = Throttled(key="/api/v1/users/", quota="1/m")
with throttle as rate_limit_result:
    print(f"limited: {rate_limit_result.limited}")
    call_api()

try:
    with throttle:
        call_api()
except exceptions.LimitedError as exc:
    print(exc)  # Rate limit exceeded: remaining=0, reset_after=60, retry_after=60
```

#### Wait & Retry

By default, rate limiting returns [**RateLimitResult**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#1-ratelimitresult) immediately.

You can specify a **`timeout`** to enable wait-and-retry behavior. The rate limiter will wait according to the `retry_after` value in [**RateLimitState**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#2-ratelimitstate) and retry automatically.

Returns the final [**RateLimitResult**](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#1-ratelimitresult) when the request is allowed or timeout reached.

```python
from throttled import RateLimiterType, Throttled, utils

throttle = Throttled(
    using=RateLimiterType.GCRA.value,
    quota="100/s burst 100",
    # ⏳ Set timeout=1 to enable wait-and-retry (max wait 1 second)
    timeout=1,
)

def call_api() -> bool:
    # ⬆️⏳ Function-level timeout overrides global timeout
    result = throttle.limit("/ping", cost=1, timeout=1)
    return result.limited

if __name__ == "__main__":
    # 👇 The actual QPS is close to the preset quota (100 req/s):
    # ✅ Total: 1000, 🕒 Latency: 35.8103 ms/op, 🚀 Throughput: 111 req/s (--)
    # ❌ Denied: 8 requests
    benchmark: utils.Benchmark = utils.Benchmark()
    denied_num: int = sum(benchmark.concurrent(call_api, 1_000, workers=4))
    print(f"❌ Denied: {denied_num} requests")
```

### 2) Storage Backends

#### Redis

You only need very simple configuration, and it supports connecting to Redis standalone, sentinel, and cluster modes.

The following example uses Redis as the storage backend, `options` supports all Redis configuration items, see [RedisStore Options](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#redisstore-options).

```python
from throttled import RateLimiterType, Throttled, store

@Throttled(
    key="/api/products",
    using=RateLimiterType.TOKEN_BUCKET.value,
    quota="1/m",
    store=store.RedisStore(
        # Standalone mode
        server="redis://127.0.0.1:6379/0",
        # Sentinel mode
        # server="redis+sentinel://:yourpassword@host1:26379,host2:26379/mymaster"
        # Cluster mode
        # server="redis+cluster://:yourpassword@host1:6379,host2:6379",
        options={}
    ),
)
def products() -> list:
    return [{"name": "iPhone"}, {"name": "MacBook"}]

products()  # Success
products()  # Raises LimitedError
```

#### In-Memory

By default, a global `MemoryStore` instance with a maximum capacity of 1024 is used as the storage backend when no storage backend is specified. Therefore, **it is usually not necessary to manually create** a `MemoryStore` instance.

Different instances mean different storage spaces, if you want to throttle the same Key at different locations in your program, make sure that Throttled receives the same MemoryStore and uses a consistent [`Quota`](https://github.com/ZhuoZhuoCrayon/throttled-py?tab=readme-ov-file#3-quota).

The following example uses memory as the storage backend and throttles the same Key on ping and pong:

```python
from throttled import Throttled, store

mem_store = store.MemoryStore()

@Throttled(key="ping-pong", quota="1/m", store=mem_store)
def ping() -> str: return "ping"

@Throttled(key="ping-pong", quota="1/m", store=mem_store)
def pong() -> str: return "pong"

ping()  # Success
pong()  # Raises LimitedError
```

### 3) Algorithms

The rate limiting algorithm is specified by the **`using`** parameter. The supported algorithms are as follows:

* [Fixed window](https://github.com/ZhuoZhuoCrayon/throttled-py/tree/main/docs/basic#21-%E5%9B%BA%E5%AE%9A%E7%AA%97%E5%8F%A3%E8%AE%A1%E6%95%B0%E5%99%A8): `RateLimiterType.FIXED_WINDOW.value`
* [Sliding window](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#22-%E6%BB%91%E5%8A%A8%E7%AA%97%E5%8F%A3): `RateLimiterType.SLIDING_WINDOW.value`
* [Token Bucket](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#23-%E4%BB%A4%E7%89%8C%E6%A1%B6): `RateLimiterType.TOKEN_BUCKET.value`
* [Leaky Bucket](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#24-%E6%BC%8F%E6%A1%B6): `RateLimiterType.LEAKING_BUCKET.value`
* [Generic Cell Rate Algorithm, GCRA](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/docs/basic/readme.md#25-gcra): `RateLimiterType.GCRA.value`

```python
from throttled import RateLimiterType, Throttled

throttle = Throttled(
    # 🌟Specifying a current limiting algorithm
    using=RateLimiterType.FIXED_WINDOW.value, 
    quota="1/m"
)
assert throttle.limit("key", 2).limited is True
```

### 4) Quota Configuration

```python
from throttled import Throttled

throttle = Throttled(
    key="/api/ping",
    quota="100/s",
    # quota="100/s burst 200",
    # quota="100 per second",
    # quota="100 per second burst 200",
)

if __name__ == "__main__":
    print(throttle.limit())
```

* *[1]* `quota` accepts a readable string with these patterns:

* `n / unit`
 * `n / unit burst <burst>`
 * `n per unit`
 * `n per unit burst <burst>`

* *[2]* `unit` supports `s / m / h / d / w`.

* *[3]* `burst` means extra bucket capacity for traffic spikes, and takes effect for: `TOKEN_BUCKET` / `LEAKING_BUCKET` / `GCRA`.

* *[4]* If `burst` is omitted in string mode, it defaults to `n` in the same rule.
  For example, `1/s` is equivalent to `1/s burst 1`.

## ⚙️ Data Models & Configuration

### 1) RateLimitResult

RateLimitState represents the result after executing the RateLimiter for the given key.

| Field     | Type           | Description                                                                             |
|-----------|----------------|-----------------------------------------------------------------------------------------|
| `limited` | bool           | Limited represents whether this request is allowed to pass.                             |
| `state`   | RateLimitState | RateLimitState represents the result after executing the RateLimiter for the given key. |

### 2) RateLimitState

RateLimitState represents the current state of the rate limiter for the given key.

| Field         | Type  | Description                                                                                                                          |
|---------------|-------|--------------------------------------------------------------------------------------------------------------------------------------|
| `limit`       | int   | Limit represents the maximum number of requests allowed to pass in the initial state.                                                |
| `remaining`   | int   | Remaining represents the maximum number of requests allowed to pass for the given key in the current state.                          |
| `reset_after` | float | ResetAfter represents the time in seconds for the RateLimiter to return to its initial state. In the initial state, Limit=Remaining. |
| `retry_after` | float | RetryAfter represents the time in seconds for the request to be retried, 0 if the request is allowed.                                |

### 3) Quota

Quota represents the quota limit configuration.

| Field   | Type | Description                                                                                                    |
|---------|------|----------------------------------------------------------------------------------------------------------------|
| `burst` | int  | Optional burst capacity that allows exceeding the rate limit momentarily(supports Token / Leaky Bucket, GCRA). |
| `rate`  | Rate | The base rate limit configuration.                                                                             |

### 4) Rate

Rate represents the rate limit configuration.

| Field    | Type               | Description                                                         |
|----------|--------------------|---------------------------------------------------------------------|
| `period` | datetime.timedelta | The time period for which the rate limit applies.                   |
| `limit`  | int                | The maximum number of requests allowed within the specified period. |

### 5) Store Configuration

#### Common Parameters

| Param     | Description                                                                      | Default                      |
|-----------|----------------------------------------------------------------------------------|------------------------------|
| `server`  | Redis connection URL, you can use it to connect to Redis in any deployment mode. | `"redis://localhost:6379/0"` |
| `options` | Storage-specific configurations                                                  | `{}`                         |

#### RedisStore Options

RedisStore is developed based on the Redis API provided by [redis-py](https://github.com/redis/redis-py).

In terms of Redis connection configuration management, the configuration naming of [django-redis](https://github.com/jazzband/django-redis) is basically used to reduce the learning cost.

| Parameter | Description | Default |
|----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `SOCKET_TIMEOUT` | ConnectionPool parameters. | `null` |
| `SOCKET_CONNECT_TIMEOUT` | ConnectionPool parameters. | `null` |
| `CONNECTION_POOL_KWARGS` | [ConnectionPool construction parameters](https://redis.readthedocs.io/en/stable/connections.html#connectionpool). | `{}` |
| `REDIS_CLIENT_KWARGS` | [RedisClient construction parameters](https://redis.readthedocs.io/en/stable/connections.html#redis.Redis). | `{}` |
| `SENTINEL_KWARGS` | [Sentinel construction parameters](https://redis.readthedocs.io/en/stable/connections.html#id1). | `{}` |
| `CONNECTION_FACTORY_CLASS` | ConnectionFactory is used to create and maintain [ConnectionPool](https://redis.readthedocs.io/en/stable/connections.html#redis.connection.ConnectionPool). | Automatically select via the `server` scheme by default. Standalone: `"throttled.store.ConnectionFactory"` Sentinel:`"throttled.store.SentinelConnectionFactory"` Cluster: `"throttled.store.ClusterConnectionFactory"` |
| `REDIS_CLIENT_CLASS` | RedisClient import path. | Automatically select sync/async mode by default. Sync(Standalone/Sentinel): `"redis.client.Redis"` Async(Standalone/Sentinel): `"redis.asyncio.client.Redis"` Sync(Cluster): ``"redis.cluster.RedisCluster"`` Async(Cluster): ``"redis.asyncio.cluster.RedisCluster"`` |
| `CONNECTION_POOL_CLASS` | ConnectionPool import path. | Automatically select via the `server` scheme and sync/async mode by default. Sync(Standalone): `"redis.connection.ConnectionPool"` Async(Standalone): `"redis.asyncio.connection.ConnectionPool"` Sync(Sentinel): `"redis.sentinel.SentinelConnectionPool"` Async(Sentinel): `"redis.asyncio.sentinel.SentinelConnectionPool"` Cluster: `"Disabled"` |
| `SENTINEL_CLASS` | Sentinel import path. | Automatically select sync/async mode by default. Sync: `"redis.Sentinel"` Async: `"redis.asyncio.Sentinel"` |

#### MemoryStore Options

MemoryStore is essentially a [LRU Cache](https://en.wikipedia.org/wiki/Cache_replacement_policies#LRU) based on memory with expiration time.

| Parameter  | Description                                                                                                                          | Default |
|------------|--------------------------------------------------------------------------------------------------------------------------------------|---------|
| `MAX_SIZE` | Maximum capacity. When the number of stored key-value pairs exceeds `MAX_SIZE`, they will be eliminated according to the LRU policy. | `1024`  |

### 6) Exception

All exceptions inherit from `throttled.exceptions.BaseThrottledError`.

#### LimitedError

When a request is throttled, an exception is thrown, such as: `Rate limit exceeded: remaining=0, reset_after=60, retry_after=60.`.

| Field               | Type              | Description                                                   |
|---------------------|-------------------|---------------------------------------------------------------|
| `rate_limit_result` | `RateLimitResult` | The result after executing the RateLimiter for the given key. |

#### DataError

Thrown when the parameter is invalid, such as: `Invalid key: None, must be a non-empty key.`.

## 📊 Benchmarks

### 1) Test Environment
- **Python Version**: 3.13.1 (CPython implementation)
- **Operating System**: macOS Darwin 23.6.0 (ARM64 architecture)
- **Redis Version**: 7.x (local connection)

### 2) Performance Metrics
> Throughput in req/s, Latency in ms/op.

| Algorithm Type     | In-Memory (Single-thread) | In-Memory (16 threads)     | Redis (Single-thread) | Redis (16 threads)  |
|--------------------|---------------------------|----------------------------|-----------------------|---------------------|
| **Baseline** *[1]* | **1,692,307 / 0.0002**    | **135,018 / 0.0004** *[2]* | **17,324 / 0.0571**   | **16,803 / 0.9478** |
| Fixed Window       | 369,635 / 0.0023          | 57,275 / 0.2533            | 16,233 / 0.0610       | 15,835 / 1.0070     |
| Sliding Window     | 265,215 / 0.0034          | 49,721 / 0.2996            | 12,605 / 0.0786       | 13,371 / 1.1923     |
| Token Bucket       | 365,678 / 0.0023          | 54,597 / 0.2821            | 13,643 / 0.0727       | 13,219 / 1.2057     |
| Leaky Bucket       | 364,296 / 0.0023          | 54,136 / 0.2887            | 13,628 / 0.0727       | 12,579 / 1.2667     |
| GCRA               | 373,906 / 0.0023          | 53,994 / 0.2895            | 12,901 / 0.0769       | 12,861 / 1.2391     |

* *[1] Baseline: In-Memory - `dict[key] += 1`, Redis - `INCRBY key increment`*.
* *[2] In-Memory concurrent baseline uses `threading.RLock` for thread safety.*
* *[3] Performance: In-Memory - ~2.5-4.5x `dict[key] += 1` operations, Redis - ~1.06-1.37x `INCRBY key increment` operations.*
* *[4] Benchmark code: [tests/benchmarks/test_throttled.py](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/tests/benchmarks/test_throttled.py).*

## 🍃 Inspiration

[Rate Limiting, Cells, and GCRA](https://brandur.org/rate-limiting), by [Brandur Leach](https://github.com/brandur)

## 📚 Version History

[See CHANGELOG](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/CHANGELOG_EN.rst)

## 📄 License

[The MIT License](https://github.com/ZhuoZhuoCrayon/throttled-py/blob/main/LICENSE)

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