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chi

by go-chi

go-chi /chi

lightweight, idiomatic and composable router for building Go HTTP services

7.8K Stars 534 Forks Last release: about 1 month ago (v4.1.2) MIT License 599 Commits 29 Releases

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chi

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chi

is a lightweight, idiomatic and composable router for building Go HTTP services. It's especially good at helping you write large REST API services that are kept maintainable as your project grows and changes.

chi

is built on the new

context

package introduced in Go 1.7 to handle signaling, cancelation and request-scoped values across a handler chain.

The focus of the project has been to seek out an elegant and comfortable design for writing REST API servers, written during the development of the Pressly API service that powers our public API service, which in turn powers all of our client-side applications.

The key considerations of chi's design are: project structure, maintainability, standard http handlers (stdlib-only), developer productivity, and deconstructing a large system into many small parts. The core router

github.com/go-chi/chi

is quite small (less than 1000 LOC), but we've also included some useful/optional subpackages: middleware, render and docgen. We hope you enjoy it too!

Install

go get -u github.com/go-chi/chi

Features

  • Lightweight - cloc'd in ~1000 LOC for the chi router
  • Fast - yes, see benchmarks
  • 100% compatible with net/http - use any http or middleware pkg in the ecosystem that is also compatible with
    net/http
  • Designed for modular/composable APIs - middlewares, inline middlewares, route groups and subrouter mounting
  • Context control - built on new
    context
    package, providing value chaining, cancellations and timeouts
  • Robust - in production at Pressly, CloudFlare, Heroku, 99Designs, and many others (see discussion)
  • Doc generation -
    docgen
    auto-generates routing documentation from your source to JSON or Markdown
  • No external dependencies - plain ol' Go stdlib + net/http

Examples

See _examples/ for a variety of examples.

As easy as:

package main import ( "net/http" "github.com/go-chi/chi" "github.com/go-chi/chi/middleware" ) func main() { r := chi.NewRouter() r.Use(middleware.Logger) r.Get("/", func(w http.ResponseWriter, r \*http.Request) { w.Write([]byte("welcome")) }) http.ListenAndServe(":3000", r) }

REST Preview:

Here is a little preview of how routing looks like with chi. Also take a look at the generated routing docs in JSON (routes.json) and in Markdown (routes.md).

I highly recommend reading the source of the examples listed above, they will show you all the features of chi and serve as a good form of documentation.

import ( //... "context" "github.com/go-chi/chi" "github.com/go-chi/chi/middleware" ) func main() { r := chi.NewRouter() // A good base middleware stack r.Use(middleware.RequestID) r.Use(middleware.RealIP) r.Use(middleware.Logger) r.Use(middleware.Recoverer) // Set a timeout value on the request context (ctx), that will signal // through ctx.Done() that the request has timed out and further // processing should be stopped. r.Use(middleware.Timeout(60 \* time.Second)) r.Get("/", func(w http.ResponseWriter, r \*http.Request) { w.Write([]byte("hi")) }) // RESTy routes for "articles" resource r.Route("/articles", func(r chi.Router) { r.With(paginate).Get("/", listArticles) // GET /articles r.With(paginate).Get("/{month}-{day}-{year}", listArticlesByDate) // GET /articles/01-16-2017 r.Post("/", createArticle) // POST /articles r.Get("/search", searchArticles) // GET /articles/search // Regexp url parameters: r.Get("/{articleSlug:[a-z-]+}", getArticleBySlug) // GET /articles/home-is-toronto // Subrouters: r.Route("/{articleID}", func(r chi.Router) { r.Use(ArticleCtx) r.Get("/", getArticle) // GET /articles/123 r.Put("/", updateArticle) // PUT /articles/123 r.Delete("/", deleteArticle) // DELETE /articles/123 }) }) // Mount the admin sub-router r.Mount("/admin", adminRouter()) http.ListenAndServe(":3333", r) } func ArticleCtx(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r \*http.Request) { articleID := chi.URLParam(r, "articleID") article, err := dbGetArticle(articleID) if err != nil { http.Error(w, http.StatusText(404), 404) return } ctx := context.WithValue(r.Context(), "article", article) next.ServeHTTP(w, r.WithContext(ctx)) }) } func getArticle(w http.ResponseWriter, r \*http.Request) { ctx := r.Context() article, ok := ctx.Value("article").(\*Article) if !ok { http.Error(w, http.StatusText(422), 422) return } w.Write([]byte(fmt.Sprintf("title:%s", article.Title))) } // A completely separate router for administrator routes func adminRouter() http.Handler { r := chi.NewRouter() r.Use(AdminOnly) r.Get("/", adminIndex) r.Get("/accounts", adminListAccounts) return r } func AdminOnly(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r \*http.Request) { ctx := r.Context() perm, ok := ctx.Value("acl.permission").(YourPermissionType) if !ok || !perm.IsAdmin() { http.Error(w, http.StatusText(403), 403) return } next.ServeHTTP(w, r) }) }

Router interface

chi's router is based on a kind of Patricia Radix trie. The router is fully compatible with

net/http

.

Built on top of the tree is the

Router

interface:

// Router consisting of the core routing methods used by chi's Mux, // using only the standard net/http. type Router interface { http.Handler Routes // Use appends one or more middlewares onto the Router stack. Use(middlewares ...func(http.Handler) http.Handler) // With adds inline middlewares for an endpoint handler. With(middlewares ...func(http.Handler) http.Handler) Router // Group adds a new inline-Router along the current routing // path, with a fresh middleware stack for the inline-Router. Group(fn func(r Router)) Router // Route mounts a sub-Router along a `pattern`` string. Route(pattern string, fn func(r Router)) Router // Mount attaches another http.Handler along ./pattern/* Mount(pattern string, h http.Handler) // Handle and HandleFunc adds routes for `pattern` that matches // all HTTP methods. Handle(pattern string, h http.Handler) HandleFunc(pattern string, h http.HandlerFunc) // Method and MethodFunc adds routes for `pattern` that matches // the `method` HTTP method. Method(method, pattern string, h http.Handler) MethodFunc(method, pattern string, h http.HandlerFunc) // HTTP-method routing along `pattern` Connect(pattern string, h http.HandlerFunc) Delete(pattern string, h http.HandlerFunc) Get(pattern string, h http.HandlerFunc) Head(pattern string, h http.HandlerFunc) Options(pattern string, h http.HandlerFunc) Patch(pattern string, h http.HandlerFunc) Post(pattern string, h http.HandlerFunc) Put(pattern string, h http.HandlerFunc) Trace(pattern string, h http.HandlerFunc) // NotFound defines a handler to respond whenever a route could // not be found. NotFound(h http.HandlerFunc) // MethodNotAllowed defines a handler to respond whenever a method is // not allowed. MethodNotAllowed(h http.HandlerFunc) } // Routes interface adds two methods for router traversal, which is also // used by the github.com/go-chi/docgen package to generate documentation for Routers. type Routes interface { // Routes returns the routing tree in an easily traversable structure. Routes() []Route // Middlewares returns the list of middlewares in use by the router. Middlewares() Middlewares // Match searches the routing tree for a handler that matches // the method/path - similar to routing a http request, but without // executing the handler thereafter. Match(rctx \*Context, method, path string) bool }

Each routing method accepts a URL

pattern

and chain of

handlers

. The URL pattern supports named params (ie.

/users/{userID}

) and wildcards (ie.

/admin/\*

). URL parameters can be fetched at runtime by calling

chi.URLParam(r, "userID")

for named parameters and

chi.URLParam(r, "\*")

for a wildcard parameter.

Middleware handlers

chi's middlewares are just stdlib net/http middleware handlers. There is nothing special about them, which means the router and all the tooling is designed to be compatible and friendly with any middleware in the community. This offers much better extensibility and reuse of packages and is at the heart of chi's purpose.

Here is an example of a standard net/http middleware where we assign a context key

"user"

the value of

"123"

. This middleware sets a hypothetical user identifier on the request context and calls the next handler in the chain.

// HTTP middleware setting a value on the request context func MyMiddleware(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r \*http.Request) { // create new context from `r` request context, and assign key `"user"` // to value of `"123"` ctx := context.WithValue(r.Context(), "user", "123") // call the next handler in the chain, passing the response writer and // the updated request object with the new context value. // // note: context.Context values are nested, so any previously set // values will be accessible as well, and the new `"user"` key // will be accessible from this point forward. next.ServeHTTP(w, r.WithContext(ctx)) }) }

Request handlers

chi uses standard net/http request handlers. This little snippet is an example of a http.Handler func that reads a user identifier from the request context - hypothetically, identifying the user sending an authenticated request, validated+set by a previous middleware handler.

// HTTP handler accessing data from the request context. func MyRequestHandler(w http.ResponseWriter, r \*http.Request) { // here we read from the request context and fetch out `"user"` key set in // the MyMiddleware example above. user := r.Context().Value("user").(string) // respond to the client w.Write([]byte(fmt.Sprintf("hi %s", user))) }

URL parameters

chi's router parses and stores URL parameters right onto the request context. Here is an example of how to access URL params in your net/http handlers. And of course, middlewares are able to access the same information.

// HTTP handler accessing the url routing parameters. func MyRequestHandler(w http.ResponseWriter, r \*http.Request) { // fetch the url parameter `"userID"` from the request of a matching // routing pattern. An example routing pattern could be: /users/{userID} userID := chi.URLParam(r, "userID") // fetch `"key"` from the request context ctx := r.Context() key := ctx.Value("key").(string) // respond to the client w.Write([]byte(fmt.Sprintf("hi %v, %v", userID, key))) }

Middlewares

chi comes equipped with an optional

middleware

package, providing a suite of standard

net/http

middlewares. Please note, any middleware in the ecosystem that is also compatible with

net/http

can be used with chi's mux.

Core middlewares


| chi/middleware Handler | description | | :--------------------- | :---------------------------------------------------------------------- | | AllowContentType | Explicit whitelist of accepted request Content-Types | | BasicAuth | Basic HTTP authentication | | Compress | Gzip compression for clients that accept compressed responses | | GetHead | Automatically route undefined HEAD requests to GET handlers | | Heartbeat | Monitoring endpoint to check the servers pulse | | Logger | Logs the start and end of each request with the elapsed processing time | | NoCache | Sets response headers to prevent clients from caching | | Profiler | Easily attach net/http/pprof to your routers | | RealIP | Sets a http.Request's RemoteAddr to either X-Forwarded-For or X-Real-IP | | Recoverer | Gracefully absorb panics and prints the stack trace | | RequestID | Injects a request ID into the context of each request | | RedirectSlashes | Redirect slashes on routing paths | | SetHeader | Short-hand middleware to set a response header key/value | | StripSlashes | Strip slashes on routing paths | | Throttle | Puts a ceiling on the number of concurrent requests | | Timeout | Signals to the request context when the timeout deadline is reached | | URLFormat | Parse extension from url and put it on request context |

| WithValue | Short-hand middleware to set a key/value on the request context |

Extra middlewares & packages

Please see https://github.com/go-chi for additional packages.


| package | description | |:---------------------------------------------------|:------------------------------------------------------------- | cors | Cross-origin resource sharing (CORS) | | docgen | Print chi.Router routes at runtime | | jwtauth | JWT authentication | | hostrouter | Domain/host based request routing | | httplog | Small but powerful structured HTTP request logging | | httprate | HTTP request rate limiter | | httptracer | HTTP request performance tracing library | | httpvcr | Write deterministic tests for external sources |

| stampede | HTTP request coalescer |

please submit a PR if you'd like to include a link to a chi-compatible middleware

context?

context

is a tiny pkg that provides simple interface to signal context across call stacks and goroutines. It was originally written by Sameer Ajmaniand is available in stdlib since go1.7.

Learn more at https://blog.golang.org/context

and.. * Docs: https://golang.org/pkg/context * Source: https://github.com/golang/go/tree/master/src/context

Benchmarks

The benchmark suite: https://github.com/pkieltyka/go-http-routing-benchmark

Results as of Jan 9, 2019 with Go 1.11.4 on Linux X1 Carbon laptop

BenchmarkChi\_Param 3000000 475 ns/op 432 B/op 3 allocs/op BenchmarkChi\_Param5 2000000 696 ns/op 432 B/op 3 allocs/op BenchmarkChi\_Param20 1000000 1275 ns/op 432 B/op 3 allocs/op BenchmarkChi\_ParamWrite 3000000 505 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GithubStatic 3000000 508 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GithubParam 2000000 669 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GithubAll 10000 134627 ns/op 87699 B/op 609 allocs/op BenchmarkChi\_GPlusStatic 3000000 402 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GPlusParam 3000000 500 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GPlus2Params 3000000 586 ns/op 432 B/op 3 allocs/op BenchmarkChi\_GPlusAll 200000 7237 ns/op 5616 B/op 39 allocs/op BenchmarkChi\_ParseStatic 3000000 408 ns/op 432 B/op 3 allocs/op BenchmarkChi\_ParseParam 3000000 488 ns/op 432 B/op 3 allocs/op BenchmarkChi\_Parse2Params 3000000 551 ns/op 432 B/op 3 allocs/op BenchmarkChi\_ParseAll 100000 13508 ns/op 11232 B/op 78 allocs/op BenchmarkChi\_StaticAll 20000 81933 ns/op 67826 B/op 471 allocs/op

Comparison with other routers: https://gist.github.com/pkieltyka/123032f12052520aaccab752bd3e78cc

NOTE: the allocs in the benchmark above are from the calls to http.Request's

WithContext(context.Context)

method that clones the http.Request, sets the

Context()

on the duplicated (alloc'd) request and returns it the new request object. This is just how setting context on a request in Go works.

Credits

We'll be more than happy to see your contributions!

Beyond REST

chi is just a http router that lets you decompose request handling into many smaller layers. Many companies use chi to write REST services for their public APIs. But, REST is just a convention for managing state via HTTP, and there's a lot of other pieces required to write a complete client-server system or network of microservices.

Looking beyond REST, I also recommend some newer works in the field: * webrpc - Web-focused RPC client+server framework with code-gen * gRPC - Google's RPC framework via protobufs * graphql - Declarative query language * NATS - lightweight pub-sub

License

Copyright (c) 2015-present Peter Kieltyka

Licensed under MIT License

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