FastRoute

Insanely simple, idiomatic and fast - 200 loc http router for golang. Uses standard http.Handler and has no limitations to path matching compared to routers derived from Trie (radix) tree based solutions.

Less is exponentially more

fastroute.Router interface extends http.Handler with one extra method - Route in order to route http.Request to http.Handler allowing to chain routes until one is matched.

Go is about composition

The gravest problem all routers have - is the central structure holding all the context.

fastroute is extremely flexible, because it has only static, unbounded functions. Allows unlimited ways to compose router.

See the following example:

package main

import (
	"fmt"
	"net/http"

	fr "github.com/DATA-DOG/fastroute"
)

var routes = map[string]fr.Router{
	"GET": fr.Chain(
		fr.New("/", handler),
		fr.New("/hello/:name/:surname", handler),
		fr.New("/hello/:name", handler),
	),
	"POST": fr.Chain(
		fr.New("/users", handler),
		fr.New("/users/:id", handler),
	),
}

var router = fr.RouterFunc(func(req *http.Request) http.Handler {
	return routes[req.Method] // fastroute.Router is also http.Handler
})

func main() {
	http.ListenAndServe(":8080", router)
}

func handler(w http.ResponseWriter, req *http.Request) {
	fmt.Fprintln(w, fmt.Sprintf(
		`%s "%s", pattern: "%s", parameters: "%v"`,
		req.Method,
		req.URL.Path,
		fr.Pattern(req),
		fr.Parameters(req),
	))
}

In overall, it is not all in one router, it is the same http.Handler with do it yourself style, but with zero allocations path pattern matching. Feel free to just copy it and adapt to your needs.

It deserves a quote from Rob Pike:

Fancy algorithms are slow when n is small, and n is usually small. Fancy algorithms have big constants. Until you know that n is frequently going to be big, don't get fancy.

The trade off this router makes is the size of n. Instead it provides orthogonal building blocks, just like http.Handler does, in order to build customized routers.

Guides

Here are some common usage guidelines:

Custom Not Found handler

Since fastroute.Router returns nil if request is not matched, we can easily extend it and create middleware for it at as many levels as we like.

package main

import (
	"fmt"
	"net/http"

	"github.com/DATA-DOG/fastroute"
)

func main() {
	notFoundHandler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		w.WriteHeader(404)
		fmt.Fprintln(w, "Ooops, looks like you mistyped the URL:", req.URL.Path)
	})

	router := fastroute.New("/users/:id", func(w http.ResponseWriter, req *http.Request) {
		fmt.Fprintln(w, "user:", fastroute.Parameters(req).ByName("id"))
	})

	http.ListenAndServe(":8080", fastroute.RouterFunc(func(req *http.Request) http.Handler {
		if h := router.Route(req); h != nil {
			return h
		}
		return notFoundHandler
	}))
}

This way, it is possible to extend fastroute.Router with various middleware, including:

• Method not found handler.
• Fixed path or trailing slash redirects. Based on your chosen route layout.
• Options or CORS.

Hit counting frequently accessed routes

In cases where n number of routes is very high and it is unknown what routes would be most frequently accessed or it changes during runtime, in order to highly improve performance, you can use hit count based reordering middleware.

package main

import (
	"fmt"
	"net/http"
	"sort"

	fr "github.com/DATA-DOG/fastroute"
)

var routes = map[string]fr.Router{
	"GET": fr.Chain(
		// here follows frequently accessed routes
		HitCountingOrderedChain(
			fr.New("/", handler),
			fr.New("/health", handler),
			fr.New("/status", handler),
		),
		// less frequently accessed routes
		fr.New("/hello/:name/:surname", handler),
		fr.New("/hello/:name", handler),
	),
	"POST": fr.Chain(
		fr.New("/users", handler),
		fr.New("/users/:id", handler),
	),
}

// serves routes by request method
var router = fr.RouterFunc(func(req *http.Request) http.Handler {
	return routes[req.Method] // fastroute.Router is also http.Handler
})

func main() {
	http.ListenAndServe(":8080", router)
}

func HitCountingOrderedChain(routes ...fr.Router) fr.Router {
	type HitCounter struct {
		fr.Router
		hits int64
	}

	hitRoutes := make([]*HitCounter, len(routes))
	for i, r := range routes {
		hitRoutes[i] = &HitCounter{Router: r}
	}

	return fr.RouterFunc(func(req *http.Request) http.Handler {
		for i, r := range hitRoutes {
			if h := r.Route(req); h != nil {
				r.hits++
				// reorder route hit is behind one third of routes
				if i > len(hitRoutes)*30/100 {
					sort.Slice(hitRoutes, func(i, j int) bool {
						return hitRoutes[i].hits > hitRoutes[j].hits
					})
				}
				return h
			}
		}
		return nil
	})
}

func handler(w http.ResponseWriter, req *http.Request) {
	fmt.Fprintln(w, fmt.Sprintf(
		`%s "%s", pattern: "%s", parameters: "%v"`,
		req.Method,
		req.URL.Path,
		fr.Pattern(req),
		fr.Parameters(req),
	))
}

Method not found support

Fastroute provides way to check whether request can be served, not only serve it. Though, the parameters then must be recycled in order to prevent leaking. When a routed request is served, it automatically recycles.

package main

import (
	"fmt"
	"net/http"
	"strings"

	fr "github.com/DATA-DOG/fastroute"
)

var routes = map[string]fr.Router{
	"GET":    fr.New("/users", handler),
	"POST":   fr.New("/users/:id", handler),
	"PUT":    fr.New("/users/:id", handler),
	"DELETE": fr.New("/users/:id", handler),
}

var router = fr.RouterFunc(func(req *http.Request) http.Handler {
	return routes[req.Method] // fastroute.Router is also http.Handler
})

var app = fr.RouterFunc(func(req *http.Request) http.Handler {
	if h := router.Route(req); h != nil {
		return h // routed and can be served
	}

	var allows []string
	for method, routes := range routes {
		if h := routes.Route(req); h != nil {
			allows = append(allows, method)
			fr.Recycle(req) // we will not serve it, need to recycle
		}
	}

	if len(allows) == 0 {
		return nil
	}

	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		w.Header().Set("Allow", strings.Join(allows, ","))
		w.WriteHeader(http.StatusMethodNotAllowed)
		fmt.Fprintln(w, http.StatusText(http.StatusMethodNotAllowed))
	})
})

func main() {
	http.ListenAndServe(":8080", app)
}

func handler(w http.ResponseWriter, req *http.Request) {
	fmt.Fprintln(w, fmt.Sprintf(
		`%s "%s", pattern: "%s", parameters: "%v"`,
		req.Method,
		req.URL.Path,
		fr.Pattern(req),
		fr.Parameters(req),
	))
}

If we make a request: curl -i http://localhost:8080/users/1, we will get:

HTTP/1.1 405 Method Not Allowed
Allow: PUT,DELETE,POST
Date: Fri, 19 May 2017 06:09:56 GMT
Content-Length: 19
Content-Type: text/plain; charset=utf-8

Method Not Allowed

Combining static routes

The best and fastest way to match static routes - is to have a map of path -> handler pairs.

package main

import (
	"fmt"
	"net/http"

	"github.com/DATA-DOG/fastroute"
)

func main() {
	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		fmt.Fprintln(w, req.URL.Path, fastroute.Parameters(req))
	})

	static := map[string]http.Handler{
		"/status":      handler,
		"/users/roles": handler,
	}

	staticRoutes := fastroute.RouterFunc(func(req *http.Request) http.Handler {
		return static[req.URL.Path]
	})

	dynamicRoutes := fastroute.Chain(
		fastroute.New("/users/:id", handler),
		fastroute.New("/users/:id/roles", handler),
	)

	http.ListenAndServe(":8080", fastroute.Chain(staticRoutes, dynamicRoutes))
}

Trailing slash or fixed path redirects

In cases when your API faces public, it might be a good idea to redirect with corrected request URL if user makes a simple mistake.

This fixes trailing slash, case mismatch and cleaned path all at once. Note, we should follow some specific rule, how we build our path patterns in order to be able to fix them. In this case we follow all lowercase rule for static segments, parameters may match any case.

package main

import (
	"fmt"
	"net/http"
	"path"
	"strings"

	"github.com/DATA-DOG/fastroute"
)

func main() {
	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		fmt.Fprintln(w, req.URL.Path, fastroute.Parameters(req))
	})

	// we follow the lowercase rule for static segments
	router := fastroute.Chain(
		fastroute.New("/status", handler),
		fastroute.New("/users/:id", handler),
		fastroute.New("/users/:id/roles/", handler), // one with trailing slash
	)

	http.ListenAndServe(":8080", redirectTrailingOrFixedPath(router))

	// requesting: http://localhost:8080/Users/5/Roles
	// redirects: http://localhost:8080/users/5/roles/
}

func redirectTrailingOrFixedPath(router fastroute.Router) fastroute.Router {
	return fastroute.RouterFunc(func(req *http.Request) http.Handler {
		if h := router.Route(req); h != nil {
			return h // has matched, no need for fixing
		}

		p := strings.ToLower(path.Clean(req.URL.Path)) // first clean path and lowercase
		attempts := []string{p}                        // first variant with cleaned path
		if p[len(p)-1] == '/' {
			attempts = append(attempts, p[:len(p)-1]) // without trailing slash
		} else {
			attempts = append(attempts, p+"/") // with trailing slash
		}

		try, _ := http.NewRequest(req.Method, "/", nil) // make request for all attempts
		for _, attempt := range attempts {
			try.URL.Path = attempt
			if h := router.Route(try); h != nil {
				// matched, resolve fixed path and redirect
				pat, params := fastroute.Pattern(try), fastroute.Parameters(try)
				var fixed []string
				var nextParam int
				for _, segment := range strings.Split(pat, "/") {
					if strings.IndexAny(segment, ":*") != -1 {
						fixed = append(fixed, params[nextParam].Value)
						nextParam++
					} else {
						fixed = append(fixed, segment)
					}
				}
				fastroute.Recycle(try)
				return redirect(strings.Join(fixed, "/"))
			}
		}
		return nil // could not fix path
	})
}

func redirect(fixedPath string) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		req.URL.Path = fixedPath
		http.Redirect(w, req, req.URL.String(), http.StatusPermanentRedirect)
	})
}

Named routes

This is trivial to implement a package inside your project, where all your routes used may be named. And later paths built by these named routes from anywhere within your application.

package routes

import (
	"fmt"
	"strings"

	"github.com/DATA-DOG/fastroute"
)

var all = make(map[string]string)

func Named(name, path string, handler interface{}) fastroute.Router {
	if p, dup := all[name]; dup {
		panic(fmt.Sprintf(`route: "%s" at path: "%s" was already registered for path: "%s"`, name, path, p))
	}
	all[name] = path
	return fastroute.New(path, handler)
}

func Get(name string, params fastroute.Params) string {
	p, ok := all[name]
	if !ok {
		panic(fmt.Sprintf(`route: "%s" was never registered`, name))
	}
	for _, param := range params {
		if key := ":" + param.Key; strings.Index(p, key) != -1 {
			p = strings.Replace(p, key, param.Value, 1)
		} else if key = "*" + param.Key; strings.Index(p, key) != -1 {
			p = strings.Replace(p, key, param.Value, 1)
		}
	}

	if strings.IndexAny(p, ":*") != -1 {
		panic(fmt.Sprintf(`not all parameters were set: "%s" for route: "%s"`, p, name))
	}
	return p
}

Then the usage is obvious:

package main

import (
	"fmt"
	"net/http"

	"github.com/DATA-DOG/fastroute"
	"github.com/DATA-DOG/fastroute/routes" // should be somewhere in your project
)

func main() {
	router := fastroute.Chain(
		routes.Named("home", "/", handler),
		routes.Named("hello-full", "/hello/:name/:surname", handler),
	)

	fmt.Println(routes.Get("hello-full", fastroute.Params{
		{"name", "John"},
		{"surname", "Doe"},
	}))

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

func handler(w http.ResponseWriter, req *http.Request) {
	fmt.Fprintln(w, fmt.Sprintf(`%s "%s"`, req.Method, req.URL.Path))
}

Benchmarks

The benchmarks can be found here.

Benchmark type	repeats	cpu time op	mem op	mem allocs op
Gin_Param	20000000	70.9 ns/op	0 B/op	0 allocs/op
GorillaMux_Param	500000	3116 ns/op	1056 B/op	11 allocs/op
HttpRouter_Param	20000000	117 ns/op	32 B/op	1 allocs/op
FastRoute_Param	20000000	105 ns/op	0 B/op	0 allocs/op
Pat_Param	1000000	1910 ns/op	648 B/op	12 allocs/op
Gin_Param5	20000000	117 ns/op	0 B/op	0 allocs/op
GorillaMux_Param5	300000	4597 ns/op	1184 B/op	11 allocs/op
HttpRouter_Param5	3000000	487 ns/op	160 B/op	1 allocs/op
FastRoute_Param5	20000000	117 ns/op	0 B/op	0 allocs/op
Pat_Param5	300000	4717 ns/op	964 B/op	32 allocs/op
Gin_Param20	5000000	280 ns/op	0 B/op	0 allocs/op
GorillaMux_Param20	200000	11062 ns/op	3547 B/op	13 allocs/op
HttpRouter_Param20	1000000	1670 ns/op	640 B/op	1 allocs/op
FastRoute_Param20	10000000	197 ns/op	0 B/op	0 allocs/op
Pat_Param20	100000	20735 ns/op	4687 B/op	111 allocs/op
Gin_ParamWrite	10000000	170 ns/op	0 B/op	0 allocs/op
GorillaMux_ParamWrite	500000	3136 ns/op	1064 B/op	12 allocs/op
HttpRouter_ParamWrite	10000000	156 ns/op	32 B/op	1 allocs/op
FastRoute_ParamWrite	10000000	162 ns/op	0 B/op	0 allocs/op
Pat_ParamWrite	500000	3196 ns/op	1072 B/op	17 allocs/op
Gin_GithubStatic	20000000	87.3 ns/op	0 B/op	0 allocs/op
GorillaMux_GithubStatic	100000	15215 ns/op	736 B/op	10 allocs/op
HttpRouter_GithubStatic	30000000	49.7 ns/op	0 B/op	0 allocs/op
FastRoute_GithubStatic	20000000	60.3 ns/op	0 B/op	0 allocs/op
Pat_GithubStatic	200000	10970 ns/op	3648 B/op	76 allocs/op
Gin_GithubParam	10000000	142 ns/op	0 B/op	0 allocs/op
GorillaMux_GithubParam	200000	9998 ns/op	1088 B/op	11 allocs/op
HttpRouter_GithubParam	5000000	301 ns/op	96 B/op	1 allocs/op
FastRoute_GithubParam	5000000	387 ns/op	0 B/op	0 allocs/op
Pat_GithubParam	200000	7083 ns/op	2464 B/op	48 allocs/op
Gin_GithubAll	50000	28162 ns/op	0 B/op	0 allocs/op
GorillaMux_GithubAll	300	5731742 ns/op	211840 B/op	2272 allocs/op
HttpRouter_GithubAll	30000	49198 ns/op	13792 B/op	167 allocs/op
FastRoute_GithubAll	10000	179753 ns/op	5 B/op	0 allocs/op
Pat_GithubAll	300	4388066 ns/op	1499571 B/op	27435 allocs/op
Gin_GPlusStatic	20000000	73.3 ns/op	0 B/op	0 allocs/op
GorillaMux_GPlusStatic	1000000	2015 ns/op	736 B/op	10 allocs/op
HttpRouter_GPlusStatic	30000000	34.0 ns/op	0 B/op	0 allocs/op
FastRoute_GPlusStatic	50000000	37.3 ns/op	0 B/op	0 allocs/op
Pat_GPlusStatic	5000000	330 ns/op	96 B/op	2 allocs/op
Gin_GPlusParam	20000000	96.9 ns/op	0 B/op	0 allocs/op
GorillaMux_GPlusParam	300000	4334 ns/op	1056 B/op	11 allocs/op
HttpRouter_GPlusParam	10000000	212 ns/op	64 B/op	1 allocs/op
FastRoute_GPlusParam	10000000	145 ns/op	0 B/op	0 allocs/op
Pat_GPlusParam	1000000	2142 ns/op	688 B/op	12 allocs/op
Gin_GPlus2Params	10000000	121 ns/op	0 B/op	0 allocs/op
GorillaMux_GPlus2Params	200000	8264 ns/op	1088 B/op	11 allocs/op
HttpRouter_GPlus2Params	10000000	232 ns/op	64 B/op	1 allocs/op
FastRoute_GPlus2Params	5000000	351 ns/op	0 B/op	0 allocs/op
Pat_GPlus2Params	200000	6557 ns/op	2256 B/op	34 allocs/op
Gin_GPlusAll	1000000	1279 ns/op	0 B/op	0 allocs/op
GorillaMux_GPlusAll	20000	66580 ns/op	13296 B/op	142 allocs/op
HttpRouter_GPlusAll	1000000	2358 ns/op	640 B/op	11 allocs/op
FastRoute_GPlusAll	500000	2546 ns/op	0 B/op	0 allocs/op
Pat_GPlusAll	30000	47673 ns/op	16576 B/op	298 allocs/op
Gin_ParseStatic	20000000	71.2 ns/op	0 B/op	0 allocs/op
GorillaMux_ParseStatic	500000	2971 ns/op	752 B/op	11 allocs/op
HttpRouter_ParseStatic	50000000	32.1 ns/op	0 B/op	0 allocs/op
FastRoute_ParseStatic	30000000	42.3 ns/op	0 B/op	0 allocs/op
Pat_ParseStatic	2000000	781 ns/op	240 B/op	5 allocs/op
Gin_ParseParam	20000000	79.2 ns/op	0 B/op	0 allocs/op
GorillaMux_ParseParam	500000	3710 ns/op	1088 B/op	12 allocs/op
HttpRouter_ParseParam	10000000	181 ns/op	64 B/op	1 allocs/op
FastRoute_ParseParam	10000000	184 ns/op	0 B/op	0 allocs/op
Pat_ParseParam	500000	3165 ns/op	1120 B/op	17 allocs/op
Gin_Parse2Params	20000000	91.5 ns/op	0 B/op	0 allocs/op
GorillaMux_Parse2Params	500000	3916 ns/op	1088 B/op	11 allocs/op
HttpRouter_Parse2Params	10000000	212 ns/op	64 B/op	1 allocs/op
FastRoute_Parse2Params	10000000	147 ns/op	0 B/op	0 allocs/op
Pat_Parse2Params	500000	2980 ns/op	832 B/op	17 allocs/op
Gin_ParseAll	1000000	2264 ns/op	0 B/op	0 allocs/op
GorillaMux_ParseAll	10000	125569 ns/op	24864 B/op	292 allocs/op
HttpRouter_ParseAll	500000	3124 ns/op	640 B/op	16 allocs/op
FastRoute_ParseAll	500000	3324 ns/op	0 B/op	0 allocs/op
Pat_ParseAll	30000	56328 ns/op	17264 B/op	343 allocs/op
Gin_StaticAll	100000	19064 ns/op	0 B/op	0 allocs/op
GorillaMux_StaticAll	1000	1536755 ns/op	115648 B/op	1578 allocs/op
FastRoute_StaticAll	200000	9149 ns/op	0 B/op	0 allocs/op
HttpRouter_StaticAll	200000	10824 ns/op	0 B/op	0 allocs/op
Pat_StaticAll	1000	1597577 ns/op	533904 B/op	11123 allocs/op

We can see that FastRoute outperforms fastest routers in some of the cases:

• Number of routes is small.
• Routes are static and served from a map.
• There are many named parameters.

FastRoute was easily adapted for this benchmark. Where static routes are served, nothing is better or faster than a static path map. FastRoute allows to build any kind of router, depending on an use case. By default it targets smaller number of routes and the weakest link is large set of dynamic routes, because these are matched one by one in order.

It always boils down to targeted case implementation. It is a general purpose router of 200 lines of source code in one file, which can be copied, understood and adapted in separate projects.

Contributions

Feel free to open a pull request. Note, if you wish to contribute an extension to public (exported methods or types) - please open an issue before to discuss whether these changes can be accepted. All backward incompatible changes are and will be treated cautiously.

License

FastRoute is licensed under the three clause BSD license