chi is a lightweight, idiomatic and composable router for building Go 1.7+ 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/pressly/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/pressly/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 compat 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, cancelations and timeouts - Robust - tested / used in production at Pressly.com, and many others
- Doc generation -
docgenauto-generates routing documentation from your source to JSON or Markdown - No external dependencies - plain ol' Go 1.7+ stdlib + net/http
- rest - REST APIs made easy, productive and maintainable
- logging - Easy structured logging for any backend
- limits - Timeouts and Throttling
- todos-resource - Struct routers/handlers, an example of another code layout style
- versions - Demo of
chi/rendersubpkg - fileserver - Easily serve static files
- graceful - Graceful context signaling and server shutdown
As easy as:
package main
import (
"net/http"
"github.com/pressly/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/pressly/chi"
"github.com/pressly/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)
// When a client closes their connection midway through a request, the
// http.CloseNotifier will cancel the request context (ctx).
r.Use(middleware.CloseNotify)
// 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.Post("/", createArticle) // POST /articles
r.Get("/search", searchArticles) // GET /articles/search
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 of 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)
// 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)
}
// Routes interface adds two methods for router traversal, which is also
// used by the `docgen` subpackage to generation 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
}Each routing method accepts a URL pattern and chain of handlers. The URL pattern
supports named params (ie. /users/:userID) and wildcards (ie. /admin/*).
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 1.7+. 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.
| Middleware | Description |
|---|---|
| RequestID | Injects a request ID into the context of each request. |
| RealIP | Sets a http.Request's RemoteAddr to either X-Forwarded-For or X-Real-IP. |
| Logger | Logs the start and end of each request with the elapsed processing time. |
| Recoverer | Gracefully absorb panics and prints the stack trace. |
| NoCache | Sets response headers to prevent clients from caching. |
| CloseNotify | Signals to the request context when a client has closed their connection. |
| Timeout | Signals to the request context when the timeout deadline is reached. |
| Throttle | Puts a ceiling on the number of concurrent requests. |
| Compress | Gzip compression for clients that accept compressed responses. |
| Profiler | Easily attach net/http/pprof to your routers. |
| Slashes | Strip and redirect slashes on routing paths. |
| WithValue | Short-hand middleware to set a key/value on the request context. |
| Heartbeat | Monitoring endpoint to check the servers pulse. |
Other cool net/http middlewares:
please submit a PR if you'd like to include a link to a chi 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
Comparison with other routers (as of Jan 7/17): https://gist.github.com/pkieltyka/d0814d5396c996cb3ff8076399583d1f
BenchmarkChi_Param 5000000 398 ns/op 304 B/op 2 allocs/op
BenchmarkChi_Param5 3000000 556 ns/op 304 B/op 2 allocs/op
BenchmarkChi_Param20 1000000 1184 ns/op 304 B/op 2 allocs/op
BenchmarkChi_ParamWrite 3000000 443 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GithubStatic 3000000 427 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GithubParam 3000000 565 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GithubAll 10000 122143 ns/op 61716 B/op 406 allocs/op
BenchmarkChi_GPlusStatic 5000000 383 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GPlusParam 3000000 431 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GPlus2Params 3000000 500 ns/op 304 B/op 2 allocs/op
BenchmarkChi_GPlusAll 200000 6410 ns/op 3952 B/op 26 allocs/op
BenchmarkChi_ParseStatic 5000000 384 ns/op 304 B/op 2 allocs/op
BenchmarkChi_ParseParam 3000000 415 ns/op 304 B/op 2 allocs/op
BenchmarkChi_Parse2Params 3000000 450 ns/op 304 B/op 2 allocs/op
BenchmarkChi_ParseAll 100000 12124 ns/op 7904 B/op 52 allocs/op
BenchmarkChi_StaticAll 20000 78501 ns/op 47731 B/op 314 allocs/opNOTE: 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 1.7+ 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 including Pressly.com (of course) 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 ahead beyond REST, I also recommend some newer works in the field coming from gRPC, NATS, go-kit and even graphql. They're all pretty cool with their own unique approaches and benefits. Specifically, I'd look at gRPC since it makes client-server communication feel like a single program on a single computer, no need to hand-write a client library and the request/response payloads are typed contracts. NATS is pretty amazing too as a super fast and lightweight pub-sub transport that can speak protobufs, with nice service discovery - an excellent combination with gRPC.
Copyright (c) 2015-present Peter Kieltyka
Licensed under MIT License