Middlers

Go HTTP Middlewares

Installation

Add middlers package as your dependency, with go get or either of your dependency management tool.

• Dep dep ensure add -v github.com/devdinu/middlers
• Glide glide install -v github.com/devdinu/middlers

Ratelimit Middleware

middleware to ratelimit the request for N requests in a period of time. It writes header StatusTooManyRequests: 429 for blocked requests, it takes configuration

  RateLimitConfig{
    TimeWindowReset // Total wait time window for next reuest to succeed
    MaxRequests     // Total max requests, beyond this will be ratelimited
    RequestKey      // a function to fetch key from request
  }

The following middleware allows 3 successful requests in a period 1 second, and blocks others. Uses the in memory store also sets X-RateLimit-Reset with total seconds time window for which it blocks requests (config TimeWindowReset)

    keyF := func(r *http.Request) string { return r.URL.Path } // you could parse body and use the fields too
    cfg := RateLimitConfig{MaxRequests: 3, TimeWindowReset: 1000 * time.Millisecond, RequestKey: keyF} rmw := RateLimit(s, cfg)(next)
    rmw.ServeHTTP(w, r)

You could use a redis, and use the TTL an implemntation of the interface

type Store interface {
	Get(string) int
	Incr(string)
	Reset(string)
}

Request Logger Middleware

You could wrap it with a handler http.HandlerFunc or http.Handler, You could use a custom logger or log.New(io.Writer...) any interface which have Println(...interface{}) implementation.

    mw := gomw.RequestLogger(handler)
    hmw := gomw.RequestLogger(handler, customLogger) // with logger

This logs each request information as json

{"method: GET, url: /some/url, status: 200, requested_at: 2018-04-04T20:52:06+05:30, resonse_at: 2018-04-04T20:52:06+05:30, duration_ms: 132ms}

Timeout Middleware

This ensures the request process completes without timeout, else writes GatewayTimeout header

    duration := 100*time.Millisecond
    withTimeout := gomw.Timeout(duration)(handler)

This changes the http.Request context to context.WithTimeout(r.Context(), duration)

Recovery Handler

You could use this handler to recover from any panic from your handlers, and return 500 Internal Server Error.

    logger // adheres to Println(...interface{}), also could be nil
    withRecovery := gomw.Recovery(logger)(next)

Filter Middleware

Filter middleware could be used to block requests based on some predicate, you could use this to validate request based on header, url or body

   predicate := func(r *http.Request) bool {
       var result bool
       // bool to decide whether to block / pass the request
       return result
   }
   withFilter := gomw.Filter(predicate)(handler)

Stats Middleware

Stats middleware reports the url calls to stats, it uses Increment(string) interface to increment the url along with status code. host:/some/url, with status 200 would increment stats as some_url_ok http.StatusText used to convert the statuscode, and / is replaced with _

    withReporter := gomw.StatsReporter(reporter)(next)

BeforeAfter Middleware

You could run a custom function before executes before the handler, and after executes after handler completion. After is executed even if handler panics

    before := func() { ... }
    after := func() { ... }
    mw := gomw.ExecutionHooks(before, after)(next)

Middler Creation

You can create a middleware with multiple middlewares stitched by passing Option, instead of manual wrapping.

    var handler http.Handler // Your HTTP handler
    ...
    gomw.New(handler,
        gomw.Predicate(predicate),
        gomw.Logger(logger),
        gomw.InMemoryRateLimit(ratelimitConfig),
    )

you could pass other options

• gomw.RateLimitter(store, ratelimitConfig) - If you wanna use custom store instead of inmemory
• gomw.Timed(duration) - To enable the middleware to timeout with given duration

Contribution

• create issues or share your opinions/future enhancements
• clone repo and make the changes you want, new features, run

    dep ensure -v # manage dependencies
    go test -v
    golint . | grep -iEv 'exported.*should have comment'
    go vet .

fix lint and vet errors if any, and create a PR.

reach out to me dineshkumar in gophers slack.

License

This project is licensed under the MIT License - see the LICENSE file for details

TODO:

• Stats middleware report statuscode as tags
• Newrelic Transaction middleware
• Add redis/redigo pool interface based ratelimit