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!
go get -u github.com/go-chi/chi
- 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
contextpackage, providing value chaining, cancellations and timeouts - Robust - in production at Pressly, CloudFlare, Heroku, 99Designs, and many others (see discussion)
- Doc generation -
docgenauto-generates routing documentation from your source to JSON or Markdown - No external dependencies - plain ol' Go stdlib + net/http
See _examples/ for a variety of examples.
As easy as:
package main
import (
"net/http"
"github.com/go-chi/chi"
)
func main() {
r := chi.NewRouter()
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)
})
}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.
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 handler using the new request context available in Go. 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) {
ctx := context.WithValue(r.Context(), "user", "123")
next.ServeHTTP(w, r.WithContext(ctx))
})
}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) {
user := r.Context().Value("user").(string)
w.Write([]byte(fmt.Sprintf("hi %s", user)))
}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) {
userID := chi.URLParam(r, "userID") // from a route like /users/{userID}
ctx := r.Context()
key := ctx.Value("key").(string)
w.Write([]byte(fmt.Sprintf("hi %v, %v", userID, key)))
}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.
| 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 |
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 |
| httpcoala | HTTP request coalescer |
| chi-authz | Request ACL via https://github.com/hsluoyz/casbin |
| phi | Port chi to fasthttp |
please submit a PR if you'd like to include a link to a chi-compatible middleware
context is a tiny pkg that provides simple interface to signal context across call stacks
and goroutines. It was originally written by Sameer Ajmani
and is available in stdlib since go1.7.
Learn more at https://blog.golang.org/context
and..
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/opComparison 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.
- Carl Jackson for https://github.com/zenazn/goji
- Parts of chi's thinking comes from goji, and chi's middleware package sources from goji.
- Armon Dadgar for https://github.com/armon/go-radix
- Contributions: @VojtechVitek
We'll be more than happy to see your contributions!
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
Copyright (c) 2015-present Peter Kieltyka
Licensed under MIT License