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Limiter

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Dead simple rate limit middleware for Go.

  • Simple API
  • "Store" approach for backend
  • Redis support (but not tied too)
  • Middlewares: HTTP and go-json-rest

Installation

$ go get github.com/ulule/limiter

Usage

In five steps:

  • Create a limiter.Rate instance (the number of requests per period)
  • Create a limiter.Store instance (see store_redis for Redis or store_memory for in-memory)
  • Create a limiter.Limiter instance that takes store and rate instances as arguments
  • Create a middleware instance using the middleware of your choice
  • Give the limiter instance to your middleware initializer

Example:

// Create a rate with the given limit (number of requests) for the given
// period (a time.Duration of your choice).
rate := limiter.Rate{
    Period: 1 * time.Hour,
    Limit:  int64(1000),
}

// You can also use the simplified format "<limit>-<period>"", with the given
// periods:
//
// * "S": second
// * "M": minute
// * "H": hour
//
// Examples:
//
// * 5 reqs/second: "5-S"
// * 10 reqs/minute: "10-M"
// * 1000 reqs/hour: "1000-H"
//
rate, err := limiter.NewRateFromFormatted("1000-H")
if err != nil {
    panic(err)
}

// Then, create a store. Here, we use the bundled Redis store. Any store
// compliant to limiter.Store interface will do the job. The defaults are
// "limiter" as Redis key prefix and a maximum of 3 retries for the key under
// race condition.
store, err := limiter.NewRedisStore(pool)
if err != nil {
    panic(err)
}

// Alternatively, you can pass options to the store with the "WithOptions"
// function. For example, for Redis store:
store, err := limiter.NewRedisStoreWithOptions(pool, limiter.StoreOptions{
    Prefix:   "your_own_prefix",
    MaxRetry: 4,
})

if err != nil {
    panic(err)
}

// Or use a in-memory store with a goroutine which clears expired keys every 30 seconds
store := limiter.NewMemoryStore("prefix_for_keys", 30*time.Second)

// Then, create the limiter instance which takes the store and the rate as arguments.
// Now, you can give this instance to any supported middleware.
limiterInstance := limiter.NewLimiter(store, rate)

See middleware examples:

How it works

The ip address of the request is used as a key in the store.

If the key does not exist in the store we set a default value with an expiration period.

You will find two stores:

  • RedisStore: rely on TTL and incrementing the rate limit on each request
  • MemoryStore: rely on go-cache with a goroutine to clear expired keys using a default interval

When the limit is reached, a 429 HTTP code is sent.

Why Yet Another Package

You could ask us: why yet another rate limit package?

Because existing packages did not suit our needs.

We tried a lot of alternatives:

  1. Throttled. This package uses the generic cell-rate algorithm. To cite the documentation: "The algorithm has been slightly modified from its usual form to support limiting with an additional quantity parameter, such as for limiting the number of bytes uploaded". It is brillant in term of algorithm but documentation is quite unclear at the moment, we don't need burst feature for now, impossible to get a correct After-Retry (when limit exceeds, we can still make a few requests, because of the max burst) and it only supports http.Handler middleware (we use go-json-rest). Currently, we only need to return 429 and X-Ratelimit-* headers for n reqs/duration.

  2. Speedbump. Good package but maybe too lightweight. No Reset support, only one middleware for Gin framework and too Redis-coupled. We rather prefer to use a "store" approach.

  3. Tollbooth. Good one too but does both too much and too less. It limits by remote IP, path, methods, custom headers and basic auth usernames... but does not provide any Redis support (only in-memory) and a ready-to-go middleware that sets X-Ratelimit-* headers. tollbooth.LimitByRequest(limiter, r) only returns an HTTP code.

  4. ratelimit. Probably the closer to our needs but, once again, too lightweight, no middleware available and not active (last commit was in August 2014). Some parts of code (Redis) comes from this project. It should deserve much more love.

There are other many packages on GitHub but most are either too lightweight, too old (only support old Go versions) or unmaintained. So that's why we decided to create yet another one.

Contributing

Don't hesitate ;)