https://github.com/brandur/redis-cell

A Redis module that provides rate limiting in Redis as a single command.
https://github.com/brandur/redis-cell

Last synced: 3 days ago
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A Redis module that provides rate limiting in Redis as a single command.

• Host: GitHub
• URL: https://github.com/brandur/redis-cell
• Owner: brandur
• License: mit
• Created: 2016-10-29T20:27:06.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2024-09-05T21:36:05.000Z (5 months ago)
• Last Synced: 2024-10-29T15:41:07.585Z (3 months ago)
• Language: Rust
• Homepage:
• Size: 237 KB
• Stars: 1,204
• Watchers: 22
• Forks: 69
• Open Issues: 11
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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• awesome-repositories - brandur/redis-cell - A Redis module that provides rate limiting in Redis as a single command. (Rust)

README

        
# redis-cell [![Build Status](https://github.com/brandur/redis-cell/workflows/redis-cell%20CI/badge.svg)](https://github.com/brandur/redis-cell/actions)

**Warning:** This package is in "best effort" maintenance mode. I try to

respond to opened issues and keep it reasonably up-to-date with respect to the

underlying Rust toolchain, but am no longer actively developing it.

A Redis module that provides rate limiting in Redis as a single command.

Implements the fairly sophisticated [generic cell rate algorithm][gcra] (GCRA)

which provides a rolling time window and doesn't depend on a background drip

process.

The primitives exposed by Redis are perfect for doing work around rate

limiting, but because it's not built in, it's very common for companies and

organizations to implement their own rate limiting logic on top of Redis using

a mixture of basic commands and Lua scripts (I've seen this at both Heroku and

Stripe for example). This can often result in naive implementations that take a

few tries to get right. The directive of redis-cell is to provide a

language-agnostic rate limiter that's easily pluggable into many cloud

architectures.

[Informal benchmarks][benchmarks] show that redis-cell is pretty fast, taking a

little under twice as long to run as a basic Redis `SET` (very roughly 0.1 ms

per command as seen from a Redis client).

## Install

[Binaries for redis-cell are available for Mac and Linux][releases]. Open

an issue if there's interest in having binaries for architectures or operating

systems that are not currently supported.

Download and extract the library, then move it somewhere that Redis can access

it (note that the extension will be **.dylib** instead of **.so** for Mac

releases):

```

$ tar -zxf redis-cell-*.tar.gz

$ cp libredis_cell.so /path/to/modules/

```

**Or**, clone and build the project from source. You'll need to [install

Rust][rust-downloads] to do so (this may be as easy as a `brew install rust` if

you're on Mac).

```

$ git clone https://github.com/brandur/redis-cell.git

$ cd redis-cell

$ cargo build --release

$ cp target/release/libredis_cell.dylib /path/to/modules/

```

**Note that Rust 1.13.0+ is required.**

Run Redis pointing to the newly built module:

```

redis-server --loadmodule /path/to/modules/libredis_cell.so

```

Alternatively add the following to a `redis.conf` file:

```

loadmodule /path/to/modules/libredis_cell.so

```

## Usage

From Redis (try running `redis-cli`) use the new `CL.THROTTLE` command loaded by

the module. It's used like this:

```

CL.THROTTLE     []

```

Where `key` is an identifier to rate limit against. Examples might be:

* A user account's unique identifier.

* The origin IP address of an incoming request.

* A static string (e.g. `global`) to limit actions across the entire system.

For example:

```

CL.THROTTLE user123 15 30 60 1

               ▲     ▲  ▲  ▲ ▲

               |     |  |  | └───── apply 1 token (default if omitted)

               |     |  └──┴─────── 30 tokens / 60 seconds

               |     └───────────── 15 max_burst

               └─────────────────── key "user123"

```

### Response

This means that a single token (the `1` in the last parameter) should be

applied against the rate limit of the key `user123`. 30 tokens on the key are

allowed over a 60 second period with a maximum initial burst of 15 tokens. Rate

limiting parameters are provided with every invocation so that limits can

easily be reconfigured on the fly.

The command will respond with an array of integers:

```

127.0.0.1:6379> CL.THROTTLE user123 15 30 60

1) (integer) 0

2) (integer) 16

3) (integer) 15

4) (integer) -1

5) (integer) 2

```

The meaning of each array item is:

1. Whether the action was limited:

    * `0` indicates the action is allowed.

    * `1` indicates that the action was limited/blocked.

2. The total limit of the key (`max_burst` + 1). This is equivalent to the

   common `X-RateLimit-Limit` HTTP header.

3. The remaining limit of the key. Equivalent to `X-RateLimit-Remaining`.

4. The number of seconds until the user should retry, and always `-1` if the

   action was allowed. Equivalent to `Retry-After`.

5. The number of seconds until the limit will reset to its maximum capacity.

   Equivalent to `X-RateLimit-Reset`.

### Multiple Rate Limits

Implement different types of rate limiting by using different key names:

```

CL.THROTTLE user123-read-rate 15 30 60

CL.THROTTLE user123-write-rate 5 10 60

```

## On Rust

redis-cell is written in Rust and uses the language's FFI module to interact

with [Redis' own module system][redis-modules]. Rust makes a very good fit here

because it doesn't need a GC and is bootstrapped with only a tiny runtime.

The author of this library is of the opinion that writing modules in Rust

instead of C will convey similar performance characteristics, but result in an

implementation that's more likely to be devoid of the bugs and memory pitfalls

commonly found in many C programs.

## License

This is free software under the terms of MIT the license (see the file

`LICENSE` for details).

## Development

### Tests and checks

Run the test suite:

    cargo test

    # specific test

    cargo test it_rates_limits

    # with debug output on stdout

    cargo test it_rates_limits -- --nocapture

CI has checks for both [Rustfmt][rustfmt] and [Clippy][clippy] (Rust's linter).

These can be installed and run locally using Rustup's component framework:

    rustup component add rustfmt

    cargo fmt --all

    rustup component add clippy

    cargo clippy -- -D warnings

### Releasing

Releases are performed automatically from a script in CI which activates when a

new tag of the format `v1.2.3` is released. The script builds binaries for all

target systems and uploads them to GitHub's [releases][releases] page.

To perform a release:

1. Add a changelog entry in `CHANGELOG.md` using the existing format.

2. Bump the version number in `Cargo.toml`.

3. Commit these changes with a message like `Bump to version 1.2.3`.

4. Tag the release with `git tag v1.2.3` (make sure to include a leading `v`).

5. `ggpush --tags`

6. Edit the new release's title and body in [GitHub][releases] (a human touch

   is still expected for the final product). Use the contents for the new

   version from `CHANGELOG.md` as the release's body, which allows Markdown

   content.

[benchmarks]: https://gist.github.com/brandur/90698498bd543598d00df46e32be3268

[clippy]: https://github.com/rust-lang/rust-clippy

[gcra]: https://en.wikipedia.org/wiki/Generic_cell_rate_algorithm

[redis-modules]: https://github.com/redis/redis-doc/blob/master/docs/reference/modules/_index.md

[releases]: https://github.com/brandur/redis-cell/releases

[rust-downloads]: https://www.rust-lang.org/en-US/downloads.html

[rustfmt]: https://github.com/rust-lang/rustfmt