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urfave/negroni

4670

urfave / negroni

Go

Idiomatic HTTP Middleware for Golang


READ ME

Negroni

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Notice: This is the library formerly known as github.com/codegangsta/negroni -- Github will automatically redirect requests to this repository, but we recommend updating your references for clarity.

Negroni is an idiomatic approach to web middleware in Go. It is tiny, non-intrusive, and encourages use of net/http Handlers.

If you like the idea of Martini, but you think it contains too much magic, then Negroni is a great fit.

Language Translations:

Getting Started

After installing Go and setting up your GOPATH, create your first .go file. We'll call it server.go.

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.Classic() // Includes some default middlewares
  n.UseHandler(mux)

  http.ListenAndServe(":3000", n)
}

Then install the Negroni package (NOTE: >= go 1.1 is required):

go get github.com/urfave/negroni

Then run your server:

go run server.go

You will now have a Go net/http webserver running on localhost:3000.

Packaging

If you are on Debian, negroni is also available as a package that you can install via apt install golang-github-urfave-negroni-dev (at the time of writing, it is in the sid repositories).

Is Negroni a Framework?

Negroni is not a framework. It is a middleware-focused library that is designed to work directly with net/http.

Routing?

Negroni is BYOR (Bring your own Router). The Go community already has a number of great http routers available, and Negroni tries to play well with all of them by fully supporting net/http. For instance, integrating with Gorilla Mux looks like so:

router := mux.NewRouter()
router.HandleFunc("/", HomeHandler)

n := negroni.New(Middleware1, Middleware2)
// Or use a middleware with the Use() function
n.Use(Middleware3)
// router goes last
n.UseHandler(router)

http.ListenAndServe(":3001", n)

negroni.Classic()

negroni.Classic() provides some default middleware that is useful for most applications:

This makes it really easy to get started with some useful features from Negroni.

Handlers

Negroni provides a bidirectional middleware flow. This is done through the negroni.Handler interface:

type Handler interface {
  ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc)
}

If a middleware hasn't already written to the ResponseWriter, it should call the next http.HandlerFunc in the chain to yield to the next middleware handler. This can be used for great good:

func MyMiddleware(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
  // do some stuff before
  next(rw, r)
  // do some stuff after
}

And you can map it to the handler chain with the Use function:

n := negroni.New()
n.Use(negroni.HandlerFunc(MyMiddleware))

You can also map plain old http.Handlers:

n := negroni.New()

mux := http.NewServeMux()
// map your routes

n.UseHandler(mux)

http.ListenAndServe(":3000", n)

With()

Negroni has a convenience function called With. With takes one or more Handler instances and returns a new Negroni with the combination of the receiver's handlers and the new handlers.

// middleware we want to reuse
common := negroni.New()
common.Use(MyMiddleware1)
common.Use(MyMiddleware2)

// `specific` is a new negroni with the handlers from `common` combined with the
// the handlers passed in
specific := common.With(
	SpecificMiddleware1,
	SpecificMiddleware2
)

Run()

Negroni has a convenience function called Run. Run takes an addr string identical to http.ListenAndServe.

package main

import (
  "github.com/urfave/negroni"
)

func main() {
  n := negroni.Classic()
  n.Run(":8080")
}

If no address is provided, the PORT environment variable is used instead. If the PORT environment variable is not defined, the default address will be used. See Run for a complete description.

In general, you will want to use net/http methods and pass negroni as a Handler, as this is more flexible, e.g.:

package main

import (
  "fmt"
  "log"
  "net/http"
  "time"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.Classic() // Includes some default middlewares
  n.UseHandler(mux)

  s := &http.Server{
    Addr:           ":8080",
    Handler:        n,
    ReadTimeout:    10 * time.Second,
    WriteTimeout:   10 * time.Second,
    MaxHeaderBytes: 1 << 20,
  }
  log.Fatal(s.ListenAndServe())
}

Route Specific Middleware

If you have a route group of routes that need specific middleware to be executed, you can simply create a new Negroni instance and use it as your route handler.

router := mux.NewRouter()
adminRoutes := mux.NewRouter()
// add admin routes here

// Create a new negroni for the admin middleware
router.PathPrefix("/admin").Handler(negroni.New(
  Middleware1,
  Middleware2,
  negroni.Wrap(adminRoutes),
))

If you are using Gorilla Mux, here is an example using a subrouter:

router := mux.NewRouter()
subRouter := mux.NewRouter().PathPrefix("/subpath").Subrouter().StrictSlash(true)
subRouter.HandleFunc("/", someSubpathHandler) // "/subpath/"
subRouter.HandleFunc("/:id", someSubpathHandler) // "/subpath/:id"

// "/subpath" is necessary to ensure the subRouter and main router linkup
router.PathPrefix("/subpath").Handler(negroni.New(
  Middleware1,
  Middleware2,
  negroni.Wrap(subRouter),
))

With() can be used to eliminate redundancy for middlewares shared across routes.

router := mux.NewRouter()
apiRoutes := mux.NewRouter()
// add api routes here
webRoutes := mux.NewRouter()
// add web routes here

// create common middleware to be shared across routes
common := negroni.New(
	Middleware1,
	Middleware2,
)

// create a new negroni for the api middleware
// using the common middleware as a base
router.PathPrefix("/api").Handler(common.With(
  APIMiddleware1,
  negroni.Wrap(apiRoutes),
))
// create a new negroni for the web middleware
// using the common middleware as a base
router.PathPrefix("/web").Handler(common.With(
  WebMiddleware1,
  negroni.Wrap(webRoutes),
))

Bundled Middleware

Static

This middleware will serve files on the filesystem. If the files do not exist, it proxies the request to the next middleware. If you want the requests for non-existent files to return a 404 File Not Found to the user you should look at using http.FileServer as a handler.

Example:

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  // Example of using a http.FileServer if you want "server-like" rather than "middleware" behavior
  // mux.Handle("/public", http.FileServer(http.Dir("/home/public")))

  n := negroni.New()
  n.Use(negroni.NewStatic(http.Dir("/tmp")))
  n.UseHandler(mux)

  http.ListenAndServe(":3002", n)
}

Will serve files from the /tmp directory first, but proxy calls to the next handler if the request does not match a file on the filesystem.

Recovery

This middleware catches panics and responds with a 500 response code. If any other middleware has written a response code or body, this middleware will fail to properly send a 500 to the client, as the client has already received the HTTP response code. Additionally, an PanicHandlerFunc can be attached to report 500's to an error reporting service such as Sentry or Airbrake.

Example:

package main

import (
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    panic("oh no")
  })

  n := negroni.New()
  n.Use(negroni.NewRecovery())
  n.UseHandler(mux)

  http.ListenAndServe(":3003", n)
}

Will return a 500 Internal Server Error to each request. It will also log the stack traces as well as print the stack trace to the requester if PrintStack is set to true (the default).

Example with error handler:

package main

import (
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    panic("oh no")
  })

  n := negroni.New()
  recovery := negroni.NewRecovery()
  recovery.PanicHandlerFunc = reportToSentry
  n.Use(recovery)
  n.UseHandler(mux)

  http.ListenAndServe(":3003", n)
}

func reportToSentry(info *negroni.PanicInformation) {
    // write code here to report error to Sentry
}

The middleware simply output the informations on STDOUT by default. You can customize the output process by using the SetFormatter() function.

You can use also the HTMLPanicFormatter to display a pretty HTML when a crash occurs.

package main

import (
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    panic("oh no")
  })

  n := negroni.New()
  recovery := negroni.NewRecovery()
  recovery.Formatter = &negroni.HTMLPanicFormatter{}
  n.Use(recovery)
  n.UseHandler(mux)

  http.ListenAndServe(":3003", n)
}

Logger

This middleware logs each incoming request and response.

Example:

package main

import (
  "fmt"
  "net/http"

  "github.com/urfave/negroni"
)

func main() {
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(w, "Welcome to the home page!")
  })

  n := negroni.New()
  n.Use(negroni.NewLogger())
  n.UseHandler(mux)

  http.ListenAndServe(":3004", n)
}

Will print a log similar to:

[negroni] 2017-10-04T14:56:25+02:00 | 200 |      378µs | localhost:3004 | GET /

on each request.

You can also set your own log format by calling the SetFormat function. The format is a template string with fields as mentioned in the LoggerEntry struct. So, as an example -

l.SetFormat("[{{.Status}} {{.Duration}}] - {{.Request.UserAgent}}")

will show something like - [200 18.263µs] - Go-User-Agent/1.1

Third Party Middleware

Here is a current list of Negroni compatible middlware. Feel free to put up a PR linking your middleware if you have built one:

Middleware Author Description
authz Yang Luo ACL, RBAC, ABAC Authorization middlware based on Casbin
binding Matt Holt Data binding from HTTP requests into structs
cloudwatch Colin Steele AWS cloudwatch metrics middleware
cors Olivier Poitrey Cross Origin Resource Sharing (CORS) support
csp Awake Networks Content Security Policy (CSP) support
delay Jeff Martinez Add delays/latency to endpoints. Useful when testing effects of high latency
New Relic Go Agent Yadvendar Champawat Official New Relic Go Agent (currently in beta)
gorelic Jingwen Owen Ou New Relic agent for Go runtime
Graceful Tyler Bunnell Graceful HTTP Shutdown
gzip phyber GZIP response compression
JWT Middleware Auth0 Middleware checks for a JWT on the Authorization header on incoming requests and decodes it
logrus Dan Buch Logrus-based logger
oauth2 David Bochenski oAuth2 middleware
onthefly Alexander Rødseth Generate TinySVG, HTML and CSS on the fly
permissions2 Alexander Rødseth Cookies, users and permissions
prometheus Rene Zbinden Easily create metrics endpoint for the prometheus instrumentation tool
render Cory Jacobsen Render JSON, XML and HTML templates
RestGate Prasanga Siripala Secure authentication for REST API endpoints
secure Cory Jacobsen Middleware that implements a few quick security wins
sessions David Bochenski Session Management
stats Florent Messa Store information about your web application (response time, etc.)
VanGoH Taylor Wrobel Configurable AWS-Style HMAC authentication middleware
xrequestid Andrea Franz Middleware that assigns a random X-Request-Id header to each request
mgo session Joel James Middleware that handles creating and closing mgo sessions per request
digits Bilal Amarni Middleware that handles Twitter Digits authentication

Examples

Alexander Rødseth created mooseware, a skeleton for writing a Negroni middleware handler.

Prasanga Siripala created an effective skeleton structure for web-based Go/Negroni projects: Go-Skeleton

Live code reload?

gin and fresh both live reload negroni apps.

Essential Reading for Beginners of Go & Negroni

About

Negroni is obsessively designed by none other than the Code Gangsta