pathmatcher

README

PathMatcher

PathMatcher is a lightweight high performance HTTP request router primitive for Go, based on julienschmidt/httprouter.

In contrast to the original httprouter, pathmatcher exposes the guts of the trie multiplexer (mux for short) so you can build your own router on top of it. In particular, it associates matched paths with any generic type of your choice, not just http.Handler or httprouter.Handler. It also exposes a plain Matcher that doesn't consider the http method at all.

⚠️ This project is a work in progress and is still porting features from httprouter. ⚠️

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.

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 built-in 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.

Type Matrix

Usage

⚠️ TODO ⚠️

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

Let's start with a trivial example:

package main

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

	"github.com/infogulch/pathmatcher"
)

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

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

type Handler func(w http.ResponseWriter, r *http.Request, ps pathmatcher.Params)

func Example() {
	matcher := pathmatcher.NewHttpMatcher[Handler]()
	matcher.GET("/", Index)
	matcher.GET("/hello/:name", Hello)

	log.Fatal(http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, handler, params, _ := matcher.Find(r.Method, r.URL.Path)
		if handler != nil {
			handler(w, r, params)
		} else {
			http.NotFound(w, r)
		}
	})))
}

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 retrieved by ByName("name").

When using a http.Handler (using router.Handler or http.HandlerFunc) instead of HttpRouter's handle API using a 3rd function parameter, the named parameters are stored in the request.Context. See more below under Why doesn't this work with http.Handler?.

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.

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

Documentation

Overview

Example

package main

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

	"github.com/infogulch/pathmatcher"
)

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

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

type Handler func(w http.ResponseWriter, r *http.Request, ps pathmatcher.Params)

func main() {
	matcher := pathmatcher.NewHttpMatcher[Handler]()
	matcher.GET("/", Index)
	matcher.GET("/hello/:name", Hello)

	log.Fatal(http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, handler, params, _ := matcher.Find(r.Method, r.URL.Path)
		if handler != nil {
			handler(w, r, params)
		} else {
			http.NotFound(w, r)
		}
	})))
}

Index

• func CleanPath(p string) string
• type HttpMatcher
  • func NewHttpMatcher[V any]() (m *HttpMatcher[V])
  • func (m *HttpMatcher[V]) Add(method, path string, value V)
  • func (m *HttpMatcher[V]) Allowed(path string) string
  • func (m *HttpMatcher[V]) CONNECT(path string, value V)
  • func (m *HttpMatcher[V]) DELETE(path string, value V)
  • func (m *HttpMatcher[V]) Find(method, path string) (match string, value V, params Params, redir bool)
  • func (m *HttpMatcher[V]) GET(path string, value V)
  • func (m *HttpMatcher[V]) HEAD(path string, value V)
  • func (m *HttpMatcher[V]) OPTIONS(path string, value V)
  • func (m *HttpMatcher[V]) PATCH(path string, value V)
  • func (m *HttpMatcher[V]) POST(path string, value V)
  • func (m *HttpMatcher[V]) PUT(path string, value V)
  • func (m *HttpMatcher[V]) TRACE(path string, value V)
• type Matcher
  • func NewMatcher[V any]() (m *Matcher[V])
  • func (m *Matcher[V]) Add(path string, value V)
  • func (m *Matcher[V]) Find(path string) (match string, value V, params Params, redir bool)
• type Param
• type Params
  • func (ps Params) ByName(name string) string

Examples

• Package

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 HttpMatcher

type HttpMatcher[V any] struct {
	// contains filtered or unexported fields
}

HttpMatcher associates endpoints (methods + parameterized paths) with values.

Implemented as a map of method names to Matchers with a shared param pool.

func NewHttpMatcher

func NewHttpMatcher[V any]() (m *HttpMatcher[V])

func (*HttpMatcher[V]) Add

func (m *HttpMatcher[V]) Add(method, path string, value V)

func (*HttpMatcher[V]) Allowed

func (m *HttpMatcher[V]) Allowed(path string) string

Allowed returns an Allow list 1 based on the methods and endpoints set in the matcher.

func (*HttpMatcher[V]) CONNECT

func (m *HttpMatcher[V]) CONNECT(path string, value V)

func (*HttpMatcher[V]) DELETE

func (m *HttpMatcher[V]) DELETE(path string, value V)

func (*HttpMatcher[V]) Find

func (m *HttpMatcher[V]) Find(method, path string) (match string, value V, params Params, redir bool)

func (*HttpMatcher[V]) GET

func (m *HttpMatcher[V]) GET(path string, value V)

func (*HttpMatcher[V]) HEAD

func (m *HttpMatcher[V]) HEAD(path string, value V)

func (*HttpMatcher[V]) OPTIONS

func (m *HttpMatcher[V]) OPTIONS(path string, value V)

func (*HttpMatcher[V]) PATCH

func (m *HttpMatcher[V]) PATCH(path string, value V)

func (*HttpMatcher[V]) POST

func (m *HttpMatcher[V]) POST(path string, value V)

func (*HttpMatcher[V]) PUT

func (m *HttpMatcher[V]) PUT(path string, value V)

func (*HttpMatcher[V]) TRACE

func (m *HttpMatcher[V]) TRACE(path string, value V)

type Matcher

type Matcher[V any] struct {
	// contains filtered or unexported fields
}

Matcher associates parametrized paths with values.

It's implementation is a light wrapper around tree.go/node struct and manages a pool of parameters.

func NewMatcher

func NewMatcher[V any]() (m *Matcher[V])

func (*Matcher[V]) Add

func (m *Matcher[V]) Add(path string, value V)

func (*Matcher[V]) Find

func (m *Matcher[V]) Find(path string) (match string, value V, params Params, redir bool)

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 (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.