httprouter

README

HttpRouter

HttpRouter is a lightweight high performance HTTP request router (also called multiplexer or just mux for short) for Go.

In contrast to the default mux of Go's net/http package, this router supports variables in the routing pattern and matches against the request method. It also scales better.

The router is optimized for high performance and a small memory footprint. It scales well even with very long paths and a large number of routes. A compressing dynamic trie (radix tree) structure is used for efficient matching.

Features

Only explicit matches: With other routers, like http.ServeMux, a requested URL path could match multiple patterns. Therefore they have some awkward pattern priority rules, like longest match or first registered, first matched. By design of this router, a request can only match exactly one or no route. As a result, there are also no unintended matches, which makes it great for SEO and improves the user experience.

Stop caring about trailing slashes: Choose the URL style you like, the router automatically redirects the client if a trailing slash is missing or if there is one extra. Of course it only does so, if the new path has a handler. If you don't like it, you can turn off this behavior.

Path auto-correction: Besides detecting the missing or additional trailing slash at no extra cost, the router can also fix wrong cases and remove superfluous path elements (like ../ or //). Is CAPTAIN CAPS LOCK one of your users? HttpRouter can help him by making a case-insensitive look-up and redirecting him to the correct URL.

Parameters in your routing pattern: Stop parsing the requested URL path, just give the path segment a name and the router delivers the dynamic value to you. Because of the design of the router, path parameters are very cheap.

Zero Garbage: The matching and dispatching process generates zero bytes of garbage. The only heap allocations that are made are building the slice of the key-value pairs for path parameters, and building new context and request objects (the latter only in the standard Handler/HandlerFunc api). In the 3-argument API, if the request path contains no parameters not a single heap allocation is necessary.

Best Performance: Benchmarks speak for themselves. See below for technical details of the implementation.

No more server crashes: You can set a Panic handler to deal with panics occurring during handling a HTTP request. The router then recovers and lets the PanicHandler log what happened and deliver a nice error page.

Perfect for APIs: The router design encourages to build sensible, hierarchical RESTful APIs. Moreover it has builtin native support for OPTIONS requests and 405 Method Not Allowed replies.

Of course you can also set custom NotFound and MethodNotAllowed handlers and serve static files.

Usage

This is just a quick introduction, view the GoDoc for details.

Let's start with a trivial example:

package main

import (
    "fmt"
    "github.com/julienschmidt/httprouter"
    "net/http"
    "log"
)

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "hello, %s!\n", ps.ByName("name"))
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/hello/:name", Hello)

    log.Fatal(http.ListenAndServe(":8080", router))
}

Named parameters

As you can see, :name is a named parameter. The values are accessible via httprouter.Params, which is just a slice of httprouter.Params. You can get the value of a parameter either by its index in the slice, or by using the ByName(name) method: :name can be retrived by ByName("name").

Named parameters only match a single path segment:

Pattern: /user/:user

 /user/gordon              match
 /user/you                 match
 /user/gordon/profile      no match
 /user/                    no match

Note: Since this router has only explicit matches, you can not register static routes and parameters for the same path segment. For example you can not register the patterns /user/new and /user/:user for the same request method at the same time. The routing of different request methods is independent from each other.

Catch-All parameters

The second type are catch-all parameters and have the form *name. Like the name suggests, they match everything. Therefore they must always be at the end of the pattern:

Pattern: /src/*filepath

 /src/                     match
 /src/somefile.go          match
 /src/subdir/somefile.go   match

How does it work?

The router relies on a tree structure which makes heavy use of common prefixes, it is basically a compact prefix tree (or just Radix tree). Nodes with a common prefix also share a common parent. Here is a short example what the routing tree for the GET request method could look like:

Priority   Path             Handle
9          \                *<1>
3          ├s               nil
2          |├earch\         *<2>
1          |└upport\        *<3>
2          ├blog\           *<4>
1          |    └:post      nil
1          |         └\     *<5>
2          ├about-us\       *<6>
1          |        └team\  *<7>
1          └contact\        *<8>

Every *<num> represents the memory address of a handler function (a pointer). If you follow a path trough the tree from the root to the leaf, you get the complete route path, e.g \blog\:post\, where :post is just a placeholder (parameter) for an actual post name. Unlike hash-maps, a tree structure also allows us to use dynamic parts like the :post parameter, since we actually match against the routing patterns instead of just comparing hashes. As benchmarks show, this works very well and efficient.

Since URL paths have a hierarchical structure and make use only of a limited set of characters (byte values), it is very likely that there are a lot of common prefixes. This allows us to easily reduce the routing into ever smaller problems. Moreover the router manages a separate tree for every request method. For one thing it is more space efficient than holding a method->handle map in every single node, it also allows us to greatly reduce the routing problem before even starting the look-up in the prefix-tree.

For even better scalability, the child nodes on each tree level are ordered by priority, where the priority is just the number of handles registered in sub nodes (children, grandchildren, and so on..). This helps in two ways:

1. Nodes which are part of the most routing paths are evaluated first. This helps to make as much routes as possible to be reachable as fast as possible.
2. It is some sort of cost compensation. The longest reachable path (highest cost) can always be evaluated first. The following scheme visualizes the tree structure. Nodes are evaluated from top to bottom and from left to right.

├------------
├---------
├-----
├----
├--
├--
└-

Why doesn't this work with http.Handler?

It does! The router itself implements the http.Handler interface. Moreover the router provides convenient adapters for http.Handlers and http.HandlerFuncs which allows them to be used as a httprouter.Handle when registering a route. The only disadvantage is, that no parameter values can be retrieved when a http.Handler or http.HandlerFunc is used, since there is no efficient way to pass the values with the existing function parameters. Therefore httprouter.Handle has a third function parameter.

Just try it out for yourself, the usage of HttpRouter is very straightforward. The package is compact and minimalistic, but also probably one of the easiest routers to set up.

Where can I find Middleware X?

This package just provides a very efficient request router with a few extra features. The router is just a http.Handler, you can chain any http.Handler compatible middleware before the router, for example the Gorilla handlers. Or you could just write your own, it's very easy!

Alternatively, you could try a web framework based on HttpRouter.

Multi-domain / Sub-domains

Here is a quick example: Does your server serve multiple domains / hosts? You want to use sub-domains? Define a router per host!

// We need an object that implements the http.Handler interface.
// Therefore we need a type for which we implement the ServeHTTP method.
// We just use a map here, in which we map host names (with port) to http.Handlers
type HostSwitch map[string]http.Handler

// Implement the ServeHTTP method on our new type
func (hs HostSwitch) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// Check if a http.Handler is registered for the given host.
	// If yes, use it to handle the request.
	if handler := hs[r.Host]; handler != nil {
		handler.ServeHTTP(w, r)
	} else {
		// Handle host names for which no handler is registered
		http.Error(w, "Forbidden", 403) // Or Redirect?
	}
}

func main() {
	// Initialize a router as usual
	router := httprouter.New()
	router.GET("/", Index)
	router.GET("/hello/:name", Hello)

	// Make a new HostSwitch and insert the router (our http handler)
	// for example.com and port 12345
	hs := make(HostSwitch)
	hs["example.com:12345"] = router

	// Use the HostSwitch to listen and serve on port 12345
	log.Fatal(http.ListenAndServe(":12345", hs))
}

Basic Authentication

Another quick example: Basic Authentication (RFC 2617) for handles:

package main

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

	"github.com/julienschmidt/httprouter"
)

func BasicAuth(h httprouter.Handle, requiredUser, requiredPassword string) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
		// Get the Basic Authentication credentials
		user, password, hasAuth := r.BasicAuth()

		if hasAuth && user == requiredUser && password == requiredPassword {
			// Delegate request to the given handle
			h(w, r, ps)
		} else {
			// Request Basic Authentication otherwise
			w.Header().Set("WWW-Authenticate", "Basic realm=Restricted")
			http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
		}
	}
}

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	fmt.Fprint(w, "Not protected!\n")
}

func Protected(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	fmt.Fprint(w, "Protected!\n")
}

func main() {
	user := "gordon"
	pass := "secret!"

	router := httprouter.New()
	router.GET("/", Index)
	router.GET("/protected/", BasicAuth(Protected, user, pass))

	log.Fatal(http.ListenAndServe(":8080", router))
}

Chaining with the NotFound handler

NOTE: It might be required to set Router.HandleMethodNotAllowed to false to avoid problems.

You can use another http.Handler, for example another router, to handle requests which could not be matched by this router by using the Router.NotFound handler. This allows chaining.

Static files

The NotFound handler can for example be used to serve static files from the root path / (like an index.html file along with other assets):

// Serve static files from the ./public directory
router.NotFound = http.FileServer(http.Dir("public"))

But this approach sidesteps the strict core rules of this router to avoid routing problems. A cleaner approach is to use a distinct sub-path for serving files, like /static/*filepath or /files/*filepath.

Web Frameworks based on HttpRouter

If the HttpRouter is a bit too minimalistic for you, you might try one of the following more high-level 3rd-party web frameworks building upon the HttpRouter package:

• Ace: Blazing fast Go Web Framework
• api2go: A JSON API Implementation for Go
• Gin: Features a martini-like API with much better performance
• Goat: A minimalistic REST API server in Go
• goMiddlewareChain: An express.js-like-middleware-chain
• Hikaru: Supports standalone and Google AppEngine
• Hitch: Hitch ties httprouter, httpcontext, and middleware up in a bow
• httpway: Simple middleware extension with context for httprouter and a server with gracefully shutdown support
• kami: A tiny web framework using x/net/context
• Medeina: Inspired by Ruby's Roda and Cuba
• Neko: A lightweight web application framework for Golang
• River: River is a simple and lightweight REST server
• Roxanna: An amalgamation of httprouter, better logging, and hot reload
• siesta: Composable HTTP handlers with contexts
• xmux: xmux is a httprouter fork on top of xhandler (net/context aware)

Documentation

Overview

Package httprouter is a trie based high performance HTTP request router.

A trivial example is:

package main

import (
    "fmt"
    "github.com/julienschmidt/httprouter"
    "net/http"
    "log"
)

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "hello, %s!\n", ps.ByName("name"))
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/hello/:name", Hello)

    log.Fatal(http.ListenAndServe(":8080", router))
}

The router matches incoming requests by the request method and the path. If a handle is registered for this path and method, the router delegates the request to that function. For the methods GET, POST, PUT, PATCH and DELETE shortcut functions exist to register handles, for all other methods router.Handle can be used.

The registered path, against which the router matches incoming requests, can contain two types of parameters:

Syntax    Type
:name     named parameter
*name     catch-all parameter

Named parameters are dynamic path segments. They match anything until the next '/' or the path end:

Path: /blog/:category/:post

Requests:
 /blog/go/request-routers            match: category="go", post="request-routers"
 /blog/go/request-routers/           no match, but the router would redirect
 /blog/go/                           no match
 /blog/go/request-routers/comments   no match

Catch-all parameters match anything until the path end, including the directory index (the '/' before the catch-all). Since they match anything until the end, catch-all parameters must always be the final path element.

Path: /files/*filepath

Requests:
 /files/                             match: filepath="/"
 /files/LICENSE                      match: filepath="/LICENSE"
 /files/templates/article.html       match: filepath="/templates/article.html"
 /files                              no match, but the router would redirect

The value of parameters is saved as a slice of the Param struct, consisting each of a key and a value. The slice is passed to the Handle func as a third parameter. There are two ways to retrieve the value of a parameter:

// by the name of the parameter
user := ps.ByName("user") // defined by :user or *user

// by the index of the parameter. This way you can also get the name (key)
thirdKey   := ps[2].Key   // the name of the 3rd parameter
thirdValue := ps[2].Value // the value of the 3rd parameter

Index

• Variables
• func CleanPath(p string) string
• type Handle
• type Param
• type Params
  • func ParamsFromContext(ctx context.Context) Params
  • func (ps Params) ByName(name string) string
• type Router
  • func New() *Router
  • func (r *Router) DELETE(path string, handle Handle)
  • func (r *Router) GET(path string, handle Handle)
  • func (r *Router) HEAD(path string, handle Handle)
  • func (r *Router) Handle(method, path string, handle Handle)
  • func (r *Router) Handler(method, path string, handler http.Handler)
  • func (r *Router) HandlerFunc(method, path string, handler http.HandlerFunc)
  • func (r *Router) Lookup(method, path string) (Handle, Params, bool)
  • func (r *Router) OPTIONS(path string, handle Handle)
  • func (r *Router) PATCH(path string, handle Handle)
  • func (r *Router) POST(path string, handle Handle)
  • func (r *Router) PUT(path string, handle Handle)
  • func (r *Router) ServeFiles(path string, root http.FileSystem)
  • func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request)

Variables

var ParamsKey = paramsKey{}

ParamsKey is the request context key under which URL params are stored.

This is only present from go 1.7.

Functions

func CleanPath

func CleanPath(p string) string

CleanPath is the URL version of path.Clean, it returns a canonical URL path for p, eliminating . and .. elements.

The following rules are applied iteratively until no further processing can be done:

1. Replace multiple slashes with a single slash.
2. Eliminate each . path name element (the current directory).
3. Eliminate each inner .. path name element (the parent directory) along with the non-.. element that precedes it.
4. Eliminate .. elements that begin a rooted path: that is, replace "/.." by "/" at the beginning of a path.

If the result of this process is an empty string, "/" is returned

Types

type Handle

type Handle func(http.ResponseWriter, *http.Request, Params)

Handle is a function that can be registered to a route to handle HTTP requests. Like http.HandlerFunc, but has a third parameter for the values of wildcards (variables).

type Param

type Param struct {
	Key   string
	Value string
}

Param is a single URL parameter, consisting of a key and a value.

type Params

type Params []Param

Params is a Param-slice, as returned by the router. The slice is ordered, the first URL parameter is also the first slice value. It is therefore safe to read values by the index.

func ParamsFromContext

func ParamsFromContext(ctx context.Context) Params

ParamsFromContext pulls the URL parameters from a request context, or returns nil if none are present.

This is only present from go 1.7.

func (Params) ByName

func (ps Params) ByName(name string) string

ByName returns the value of the first Param which key matches the given name. If no matching Param is found, an empty string is returned.

type Router

type Router struct {

	// Enables automatic redirection if the current route can't be matched but a
	// handler for the path with (without) the trailing slash exists.
	// For example if /foo/ is requested but a route only exists for /foo, the
	// client is redirected to /foo with http status code 301 for GET requests
	// and 307 for all other request methods.
	RedirectTrailingSlash bool

	// If enabled, the router tries to fix the current request path, if no
	// handle is registered for it.
	// First superfluous path elements like ../ or // are removed.
	// Afterwards the router does a case-insensitive lookup of the cleaned path.
	// If a handle can be found for this route, the router makes a redirection
	// to the corrected path with status code 301 for GET requests and 307 for
	// all other request methods.
	// For example /FOO and /..//Foo could be redirected to /foo.
	// RedirectTrailingSlash is independent of this option.
	RedirectFixedPath bool

	// If enabled, the router checks if another method is allowed for the
	// current route, if the current request can not be routed.
	// If this is the case, the request is answered with 'Method Not Allowed'
	// and HTTP status code 405.
	// If no other Method is allowed, the request is delegated to the NotFound
	// handler.
	HandleMethodNotAllowed bool

	// If enabled, the router automatically replies to OPTIONS requests.
	// Custom OPTIONS handlers take priority over automatic replies.
	HandleOPTIONS bool

	// Configurable http.Handler which is called when no matching route is
	// found. If it is not set, http.NotFound is used.
	NotFound http.Handler

	// Configurable http.Handler which is called when a request
	// cannot be routed and HandleMethodNotAllowed is true.
	// If it is not set, http.Error with http.StatusMethodNotAllowed is used.
	// The "Allow" header with allowed request methods is set before the handler
	// is called.
	MethodNotAllowed http.Handler

	// Function to handle panics recovered from http handlers.
	// It should be used to generate a error page and return the http error code
	// 500 (Internal Server Error).
	// The handler can be used to keep your server from crashing because of
	// unrecovered panics.
	PanicHandler func(http.ResponseWriter, *http.Request, interface{})
	// contains filtered or unexported fields
}

Router is a http.Handler which can be used to dispatch requests to different handler functions via configurable routes

func New

func New() *Router

New returns a new initialized Router. Path auto-correction, including trailing slashes, is enabled by default.

func (*Router) DELETE

func (r *Router) DELETE(path string, handle Handle)

DELETE is a shortcut for router.Handle("DELETE", path, handle)

func (*Router) GET

func (r *Router) GET(path string, handle Handle)

GET is a shortcut for router.Handle("GET", path, handle)

func (*Router) HEAD

func (r *Router) HEAD(path string, handle Handle)

HEAD is a shortcut for router.Handle("HEAD", path, handle)

func (*Router) Handle

func (r *Router) Handle(method, path string, handle Handle)

Handle registers a new request handle with the given path and method.

For GET, POST, PUT, PATCH and DELETE requests the respective shortcut functions can be used.

This function is intended for bulk loading and to allow the usage of less frequently used, non-standardized or custom methods (e.g. for internal communication with a proxy).

func (*Router) Handler

func (r *Router) Handler(method, path string, handler http.Handler)

Handler is an adapter which allows the usage of an http.Handler as a request handle. With go 1.7+, the Params will be available in the request context under ParamsKey.

func (*Router) HandlerFunc

func (r *Router) HandlerFunc(method, path string, handler http.HandlerFunc)

HandlerFunc is an adapter which allows the usage of an http.HandlerFunc as a request handle.

func (*Router) Lookup

func (r *Router) Lookup(method, path string) (Handle, Params, bool)

Lookup allows the manual lookup of a method + path combo. This is e.g. useful to build a framework around this router. If the path was found, it returns the handle function and the path parameter values. Otherwise the third return value indicates whether a redirection to the same path with an extra / without the trailing slash should be performed.

func (*Router) OPTIONS

func (r *Router) OPTIONS(path string, handle Handle)

OPTIONS is a shortcut for router.Handle("OPTIONS", path, handle)

func (*Router) PATCH

func (r *Router) PATCH(path string, handle Handle)

PATCH is a shortcut for router.Handle("PATCH", path, handle)

func (*Router) POST

func (r *Router) POST(path string, handle Handle)

POST is a shortcut for router.Handle("POST", path, handle)

func (*Router) PUT

func (r *Router) PUT(path string, handle Handle)

PUT is a shortcut for router.Handle("PUT", path, handle)

func (*Router) ServeFiles

func (r *Router) ServeFiles(path string, root http.FileSystem)

ServeFiles serves files from the given file system root. The path must end with "/*filepath", files are then served from the local path /defined/root/dir/*filepath. For example if root is "/etc" and *filepath is "passwd", the local file "/etc/passwd" would be served. Internally a http.FileServer is used, therefore http.NotFound is used instead of the Router's NotFound handler. To use the operating system's file system implementation, use http.Dir:

router.ServeFiles("/src/*filepath", http.Dir("/var/www"))

func (*Router) ServeHTTP

func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request)

ServeHTTP makes the router implement the http.Handler interface.