This is a generic middleware to rate-limit HTTP requests.

NOTE 1: This library is considered finished.

NOTE 2: Major version changes are backward-incompatible. v2.0.0 streamlines the ugliness of the old API.

v1.0.0: This version maintains the old API but all the thirdparty modules are moved to their own repo.

v2.x.x: Brand-new API for the sake of code cleanup, thread safety, & auto-expiring data structures.

v3.x.x: Apparently we have been using golang.org/x/time/rate incorrectly. See issue #48. It always limits X number per 1 second. The time duration is not changeable, so it does not make sense to pass TTL to tollbooth.

v4.x.x: Float64 for max requests per second

v5.x.x: go.mod and go.sum

v6.x.x: Replaced go-cache with github.com/go-pkgz/expirable-cache because go-cache leaks goroutines.

v7.x.x: Replaced time/rate with embedded time/rate so that we can support more rate limit headers.

v8.x.x: Address RemoteIP vulnerability concern by replacing SetIPLookups with SetIPLookup, an explicit way to pick the IP address. New HTTPMiddleware function which is compatible with standard routers.

package main

import (
	"net/http"

	"github.com/didip/tollbooth/v8/limiter"
)

func HelloHandler(w http.ResponseWriter, req *http.Request) {
	w.Write([]byte("Hello, World!"))
}

func main() {
	// Create a request limiter per handler.
	lmt := tollbooth.NewLimiter(1, nil)

	// New in version >= 8, you must explicitly define how to pick the IP address.
	lmt.SetIPLookup(limiter.IPLookup{
		Name:           "X-Real-IP",
		IndexFromRight: 0,
	})

	// New in version >= 8, HTTPMiddleware is a standard router compatible alternative to the previously used LimitFuncHandler.
	http.Handle("/", tollbooth.HTTPMiddleware(lmt)(http.HandlerFunc(HelloHandler)))
	// Old syntax:
	// http.Handle("/", tollbooth.LimitFuncHandler(lmt, HelloHandler))

	http.ListenAndServe(":12345", nil)
}

1. Rate-limit by request's remote IP, path, methods, custom headers, & basic auth usernames.

   import (
       "time"
   
       "github.com/didip/tollbooth/v8"
       "github.com/didip/tollbooth/v8/limiter"
   )
   
   lmt := tollbooth.NewLimiter(1, nil)
   
   // or create a limiter with expirable token buckets
   // This setting means:
   // create a 1 request/second limiter and
   // every token bucket in it will expire 1 hour after it was initially set.
   lmt = tollbooth.NewLimiter(1, &limiter.ExpirableOptions{DefaultExpirationTTL: time.Hour})
   
   // New in version >= 8, you must explicitly define how to pick the IP address.
   // If IP address cannot be found, rate limiter will not be activated.
   lmt.SetIPLookup(limiter.IPLookup{
       // The name of lookup method.
       // Possible options are: RemoteAddr, X-Forwarded-For, X-Real-IP, CF-Connecting-IP
       // All other headers are considered unknown and will be ignored.
       Name: "X-Real-IP",
   
       // The index position to pick the ip address from a comma separated list.
       // The index goes from right to left.
       //
       // When there are multiple of the same headers,
       // we will concat them together in the order of first to last seen.
       // And then we pick the IP using this index position.
       IndexFromRight: 0,
   })
   
   // In version >= 8, lmt.SetIPLookups and lmt.GetIPLookups are removed.
   
   // Limit only GET and POST requests.
   lmt.SetMethods([]string{"GET", "POST"})
   
   // Limit based on basic auth usernames.
   // You add them on-load, or later as you handle requests.
   lmt.SetBasicAuthUsers([]string{"bob", "jane", "didip", "vip"})
   // You can remove them later as well.
   lmt.RemoveBasicAuthUsers([]string{"vip"})
   
   // Limit request headers containing certain values.
   // You add them on-load, or later as you handle requests.
   lmt.SetHeader("X-Access-Token", []string{"abc123", "xyz098"})
   // You can remove all entries at once.
   lmt.RemoveHeader("X-Access-Token")
   // Or remove specific ones.
   lmt.RemoveHeaderEntries("X-Access-Token", []string{"limitless-token"})
   
   // By the way, the setters are chainable. Example:
   lmt.SetMethods([]string{"GET", "POST"}).
       SetBasicAuthUsers([]string{"sansa"}).
       SetBasicAuthUsers([]string{"tyrion"})

2. Compose your own middleware by using LimitByKeys().

3. Header entries and basic auth users can expire over time (to conserve memory).

   import "time"
   
   lmt := tollbooth.NewLimiter(1, nil)
   
   // Set a custom expiration TTL for token bucket.
   lmt.SetTokenBucketExpirationTTL(time.Hour)
   
   // Set a custom expiration TTL for basic auth users.
   lmt.SetBasicAuthExpirationTTL(time.Hour)
   
   // Set a custom expiration TTL for header entries.
   lmt.SetHeaderEntryExpirationTTL(time.Hour)

4. Upon rejection, the following HTTP response headers are available to users:

   • X-Rate-Limit-Limit The maximum request limit.

   • X-Rate-Limit-Duration The rate-limiter duration.

   • X-Rate-Limit-Request-Forwarded-For The rejected request X-Forwarded-For.

   • X-Rate-Limit-Request-Remote-Addr The rejected request RemoteAddr.

   Upon both success and rejection RateLimit headers are sent:

   • RateLimit-Limit The maximum request limit within the time window (1s).

   • RateLimit-Reset The rate-limiter time window duration in seconds (always 1s).

   • RateLimit-Remaining The remaining tokens.

5. Customize your own message or function when limit is reached.

   lmt := tollbooth.NewLimiter(1, nil)
   
   // New in version >= 8, you must explicitly define how to pick the IP address.
   lmt.SetIPLookup(limiter.IPLookup{
       Name:           "X-Forwarded-For",
       IndexFromRight: 0,
   })
   
   // Set a custom message.
   lmt.SetMessage("You have reached maximum request limit.")
   
   // Set a custom content-type.
   lmt.SetMessageContentType("text/plain; charset=utf-8")
   
   // Set a custom function for rejection.
   lmt.SetOnLimitReached(func(w http.ResponseWriter, r *http.Request) { fmt.Println("A request was rejected") })

6. Tollbooth does not require external storage since it uses an algorithm called Token Bucket (Go library: golang.org/x/time/rate).

Sometimes, other frameworks require a little bit of shim to use Tollbooth. These shims below are contributed by the community, so I make no promises on how well they work. The one I am familiar with are: Chi, Gin, and Negroni.

• Chi

• Echo

• FastHTTP

• Gin

• GoRestful

• HTTPRouter

• Iris

• Negroni

• ErrStack: A small library to combine errors and also display filename and line number.

• Stopwatch: A small library to measure latency of things. Useful if you want to report latency data to Graphite.

• LaborUnion: A dynamic worker pool library.

• Gomet: Simple HTTP client & server long poll library for Go. Useful for receiving live updates without needing Websocket.

Before sending a PR with code changes, please make sure altered code is covered with tests which are passing, and that golangci-lint shows no errors.

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