# fasthttp [](https://pkg.go.dev/github.com/valyala/fasthttp) [](https://goreportcard.com/report/github.com/valyala/fasthttp)  Fast HTTP implementation for Go. ## fasthttp might not be for you! fasthttp was designed for some high performance edge cases. **Unless** your server/client needs to handle **thousands of small to medium requests per second** and needs a consistent low millisecond response time fasthttp might not be for you. **For most cases `net/http` is much better** as it's easier to use and can handle more cases. For most cases you won't even notice the performance difference. ## General info and links Currently fasthttp is successfully used by [VertaMedia](https://vertamedia.com/) in a production serving up to 200K rps from more than 1.5M concurrent keep-alive connections per physical server. [TechEmpower Benchmark round 19 results](https://www.techempower.com/benchmarks/#section=data-r19&hw=ph&test=plaintext) [Server Benchmarks](#http-server-performance-comparison-with-nethttp) [Client Benchmarks](#http-client-comparison-with-nethttp) [Install](#install) [Documentation](https://pkg.go.dev/github.com/valyala/fasthttp) [Examples from docs](https://pkg.go.dev/github.com/valyala/fasthttp#pkg-examples) [Code examples](examples) [Awesome fasthttp tools](https://github.com/fasthttp) [Switching from net/http to fasthttp](#switching-from-nethttp-to-fasthttp) [Fasthttp best practices](#fasthttp-best-practices) [Tricks with byte buffers](#tricks-with-byte-buffers) [Related projects](#related-projects) [FAQ](#faq) ## HTTP server performance comparison with [net/http](https://pkg.go.dev/net/http) In short, fasthttp server is up to 10 times faster than net/http. Below are benchmark results. *GOMAXPROCS=1* net/http server: ``` $ GOMAXPROCS=1 go test -bench=NetHTTPServerGet -benchmem -benchtime=10s BenchmarkNetHTTPServerGet1ReqPerConn 1000000 12052 ns/op 2297 B/op 29 allocs/op BenchmarkNetHTTPServerGet2ReqPerConn 1000000 12278 ns/op 2327 B/op 24 allocs/op BenchmarkNetHTTPServerGet10ReqPerConn 2000000 8903 ns/op 2112 B/op 19 allocs/op BenchmarkNetHTTPServerGet10KReqPerConn 2000000 8451 ns/op 2058 B/op 18 allocs/op BenchmarkNetHTTPServerGet1ReqPerConn10KClients 500000 26733 ns/op 3229 B/op 29 allocs/op BenchmarkNetHTTPServerGet2ReqPerConn10KClients 1000000 23351 ns/op 3211 B/op 24 allocs/op BenchmarkNetHTTPServerGet10ReqPerConn10KClients 1000000 13390 ns/op 2483 B/op 19 allocs/op BenchmarkNetHTTPServerGet100ReqPerConn10KClients 1000000 13484 ns/op 2171 B/op 18 allocs/op ``` fasthttp server: ``` $ GOMAXPROCS=1 go test -bench=kServerGet -benchmem -benchtime=10s BenchmarkServerGet1ReqPerConn 10000000 1559 ns/op 0 B/op 0 allocs/op BenchmarkServerGet2ReqPerConn 10000000 1248 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10ReqPerConn 20000000 797 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10KReqPerConn 20000000 716 ns/op 0 B/op 0 allocs/op BenchmarkServerGet1ReqPerConn10KClients 10000000 1974 ns/op 0 B/op 0 allocs/op BenchmarkServerGet2ReqPerConn10KClients 10000000 1352 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10ReqPerConn10KClients 20000000 789 ns/op 2 B/op 0 allocs/op BenchmarkServerGet100ReqPerConn10KClients 20000000 604 ns/op 0 B/op 0 allocs/op ``` *GOMAXPROCS=4* net/http server: ``` $ GOMAXPROCS=4 go test -bench=NetHTTPServerGet -benchmem -benchtime=10s BenchmarkNetHTTPServerGet1ReqPerConn-4 3000000 4529 ns/op 2389 B/op 29 allocs/op BenchmarkNetHTTPServerGet2ReqPerConn-4 5000000 3896 ns/op 2418 B/op 24 allocs/op BenchmarkNetHTTPServerGet10ReqPerConn-4 5000000 3145 ns/op 2160 B/op 19 allocs/op BenchmarkNetHTTPServerGet10KReqPerConn-4 5000000 3054 ns/op 2065 B/op 18 allocs/op BenchmarkNetHTTPServerGet1ReqPerConn10KClients-4 1000000 10321 ns/op 3710 B/op 30 allocs/op BenchmarkNetHTTPServerGet2ReqPerConn10KClients-4 2000000 7556 ns/op 3296 B/op 24 allocs/op BenchmarkNetHTTPServerGet10ReqPerConn10KClients-4 5000000 3905 ns/op 2349 B/op 19 allocs/op BenchmarkNetHTTPServerGet100ReqPerConn10KClients-4 5000000 3435 ns/op 2130 B/op 18 allocs/op ``` fasthttp server: ``` $ GOMAXPROCS=4 go test -bench=kServerGet -benchmem -benchtime=10s BenchmarkServerGet1ReqPerConn-4 10000000 1141 ns/op 0 B/op 0 allocs/op BenchmarkServerGet2ReqPerConn-4 20000000 707 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10ReqPerConn-4 30000000 341 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10KReqPerConn-4 50000000 310 ns/op 0 B/op 0 allocs/op BenchmarkServerGet1ReqPerConn10KClients-4 10000000 1119 ns/op 0 B/op 0 allocs/op BenchmarkServerGet2ReqPerConn10KClients-4 20000000 644 ns/op 0 B/op 0 allocs/op BenchmarkServerGet10ReqPerConn10KClients-4 30000000 346 ns/op 0 B/op 0 allocs/op BenchmarkServerGet100ReqPerConn10KClients-4 50000000 282 ns/op 0 B/op 0 allocs/op ``` ## HTTP client comparison with net/http In short, fasthttp client is up to 10 times faster than net/http. Below are benchmark results. *GOMAXPROCS=1* net/http client: ``` $ GOMAXPROCS=1 go test -bench='HTTPClient(Do|GetEndToEnd)' -benchmem -benchtime=10s BenchmarkNetHTTPClientDoFastServer 1000000 12567 ns/op 2616 B/op 35 allocs/op BenchmarkNetHTTPClientGetEndToEnd1TCP 200000 67030 ns/op 5028 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd10TCP 300000 51098 ns/op 5031 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd100TCP 300000 45096 ns/op 5026 B/op 55 allocs/op BenchmarkNetHTTPClientGetEndToEnd1Inmemory 500000 24779 ns/op 5035 B/op 57 allocs/op BenchmarkNetHTTPClientGetEndToEnd10Inmemory 1000000 26425 ns/op 5035 B/op 57 allocs/op BenchmarkNetHTTPClientGetEndToEnd100Inmemory 500000 28515 ns/op 5045 B/op 57 allocs/op BenchmarkNetHTTPClientGetEndToEnd1000Inmemory 500000 39511 ns/op 5096 B/op 56 allocs/op ``` fasthttp client: ``` $ GOMAXPROCS=1 go test -bench='kClient(Do|GetEndToEnd)' -benchmem -benchtime=10s BenchmarkClientDoFastServer 20000000 865 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd1TCP 1000000 18711 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd10TCP 1000000 14664 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd100TCP 1000000 14043 ns/op 1 B/op 0 allocs/op BenchmarkClientGetEndToEnd1Inmemory 5000000 3965 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd10Inmemory 3000000 4060 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd100Inmemory 5000000 3396 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd1000Inmemory 5000000 3306 ns/op 2 B/op 0 allocs/op ``` *GOMAXPROCS=4* net/http client: ``` $ GOMAXPROCS=4 go test -bench='HTTPClient(Do|GetEndToEnd)' -benchmem -benchtime=10s BenchmarkNetHTTPClientDoFastServer-4 2000000 8774 ns/op 2619 B/op 35 allocs/op BenchmarkNetHTTPClientGetEndToEnd1TCP-4 500000 22951 ns/op 5047 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd10TCP-4 1000000 19182 ns/op 5037 B/op 55 allocs/op BenchmarkNetHTTPClientGetEndToEnd100TCP-4 1000000 16535 ns/op 5031 B/op 55 allocs/op BenchmarkNetHTTPClientGetEndToEnd1Inmemory-4 1000000 14495 ns/op 5038 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd10Inmemory-4 1000000 10237 ns/op 5034 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd100Inmemory-4 1000000 10125 ns/op 5045 B/op 56 allocs/op BenchmarkNetHTTPClientGetEndToEnd1000Inmemory-4 1000000 11132 ns/op 5136 B/op 56 allocs/op ``` fasthttp client: ``` $ GOMAXPROCS=4 go test -bench='kClient(Do|GetEndToEnd)' -benchmem -benchtime=10s BenchmarkClientDoFastServer-4 50000000 397 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd1TCP-4 2000000 7388 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd10TCP-4 2000000 6689 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd100TCP-4 3000000 4927 ns/op 1 B/op 0 allocs/op BenchmarkClientGetEndToEnd1Inmemory-4 10000000 1604 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd10Inmemory-4 10000000 1458 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd100Inmemory-4 10000000 1329 ns/op 0 B/op 0 allocs/op BenchmarkClientGetEndToEnd1000Inmemory-4 10000000 1316 ns/op 5 B/op 0 allocs/op ``` ## Install ``` go get -u github.com/valyala/fasthttp ``` ## Switching from net/http to fasthttp Unfortunately, fasthttp doesn't provide API identical to net/http. See the [FAQ](#faq) for details. There is [net/http -> fasthttp handler converter](https://pkg.go.dev/github.com/valyala/fasthttp/fasthttpadaptor), but it is better to write fasthttp request handlers by hand in order to use all of the fasthttp advantages (especially high performance :) ). Important points: * Fasthttp works with [RequestHandler functions](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler) instead of objects implementing [Handler interface](https://pkg.go.dev/net/http#Handler). Fortunately, it is easy to pass bound struct methods to fasthttp: ```go type MyHandler struct { foobar string } // request handler in net/http style, i.e. method bound to MyHandler struct. func (h *MyHandler) HandleFastHTTP(ctx *fasthttp.RequestCtx) { // notice that we may access MyHandler properties here - see h.foobar. fmt.Fprintf(ctx, "Hello, world! Requested path is %q. Foobar is %q", ctx.Path(), h.foobar) } // request handler in fasthttp style, i.e. just plain function. func fastHTTPHandler(ctx *fasthttp.RequestCtx) { fmt.Fprintf(ctx, "Hi there! RequestURI is %q", ctx.RequestURI()) } // pass bound struct method to fasthttp myHandler := &MyHandler{ foobar: "foobar", } fasthttp.ListenAndServe(":8080", myHandler.HandleFastHTTP) // pass plain function to fasthttp fasthttp.ListenAndServe(":8081", fastHTTPHandler) ``` * The [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler) accepts only one argument - [RequestCtx](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx). It contains all the functionality required for http request processing and response writing. Below is an example of a simple request handler conversion from net/http to fasthttp. ```go // net/http request handler requestHandler := func(w http.ResponseWriter, r *http.Request) { switch r.URL.Path { case "/foo": fooHandler(w, r) case "/bar": barHandler(w, r) default: http.Error(w, "Unsupported path", http.StatusNotFound) } } ``` ```go // the corresponding fasthttp request handler requestHandler := func(ctx *fasthttp.RequestCtx) { switch string(ctx.Path()) { case "/foo": fooHandler(ctx) case "/bar": barHandler(ctx) default: ctx.Error("Unsupported path", fasthttp.StatusNotFound) } } ``` * Fasthttp allows setting response headers and writing response body in an arbitrary order. There is no 'headers first, then body' restriction like in net/http. The following code is valid for fasthttp: ```go requestHandler := func(ctx *fasthttp.RequestCtx) { // set some headers and status code first ctx.SetContentType("foo/bar") ctx.SetStatusCode(fasthttp.StatusOK) // then write the first part of body fmt.Fprintf(ctx, "this is the first part of body\n") // then set more headers ctx.Response.Header.Set("Foo-Bar", "baz") // then write more body fmt.Fprintf(ctx, "this is the second part of body\n") // then override already written body ctx.SetBody([]byte("this is completely new body contents")) // then update status code ctx.SetStatusCode(fasthttp.StatusNotFound) // basically, anything may be updated many times before // returning from RequestHandler. // // Unlike net/http fasthttp doesn't put response to the wire until // returning from RequestHandler. } ``` * Fasthttp doesn't provide [ServeMux](https://pkg.go.dev/net/http#ServeMux), but there are more powerful third-party routers and web frameworks with fasthttp support: * [fasthttp-routing](https://github.com/qiangxue/fasthttp-routing) * [router](https://github.com/fasthttp/router) * [lu](https://github.com/vincentLiuxiang/lu) * [atreugo](https://github.com/savsgio/atreugo) * [Fiber](https://github.com/gofiber/fiber) * [Gearbox](https://github.com/gogearbox/gearbox) Net/http code with simple ServeMux is trivially converted to fasthttp code: ```go // net/http code m := &http.ServeMux{} m.HandleFunc("/foo", fooHandlerFunc) m.HandleFunc("/bar", barHandlerFunc) m.Handle("/baz", bazHandler) http.ListenAndServe(":80", m) ``` ```go // the corresponding fasthttp code m := func(ctx *fasthttp.RequestCtx) { switch string(ctx.Path()) { case "/foo": fooHandlerFunc(ctx) case "/bar": barHandlerFunc(ctx) case "/baz": bazHandler.HandlerFunc(ctx) default: ctx.Error("not found", fasthttp.StatusNotFound) } } fasthttp.ListenAndServe(":80", m) ``` * Because creating a new channel for every request is just too expensive, so the channel returned by RequestCtx.Done() is only closed when the server is shutting down. ```go func main() { fasthttp.ListenAndServe(":8080", fasthttp.TimeoutHandler(func(ctx *fasthttp.RequestCtx) { select { case <-ctx.Done(): // ctx.Done() is only closed when the server is shutting down. log.Println("context cancelled") return case <-time.After(10 * time.Second): log.Println("process finished ok") } }, time.Second*2, "timeout")) } ``` * net/http -> fasthttp conversion table: * All the pseudocode below assumes w, r and ctx have these types: ```go var ( w http.ResponseWriter r *http.Request ctx *fasthttp.RequestCtx ) ``` * r.Body -> [ctx.PostBody()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.PostBody) * r.URL.Path -> [ctx.Path()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Path) * r.URL -> [ctx.URI()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.URI) * r.Method -> [ctx.Method()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Method) * r.Header -> [ctx.Request.Header](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHeader) * r.Header.Get() -> [ctx.Request.Header.Peek()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHeader.Peek) * r.Host -> [ctx.Host()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Host) * r.Form -> [ctx.QueryArgs()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.QueryArgs) + [ctx.PostArgs()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.PostArgs) * r.PostForm -> [ctx.PostArgs()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.PostArgs) * r.FormValue() -> [ctx.FormValue()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.FormValue) * r.FormFile() -> [ctx.FormFile()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.FormFile) * r.MultipartForm -> [ctx.MultipartForm()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.MultipartForm) * r.RemoteAddr -> [ctx.RemoteAddr()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.RemoteAddr) * r.RequestURI -> [ctx.RequestURI()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.RequestURI) * r.TLS -> [ctx.IsTLS()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.IsTLS) * r.Cookie() -> [ctx.Request.Header.Cookie()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHeader.Cookie) * r.Referer() -> [ctx.Referer()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Referer) * r.UserAgent() -> [ctx.UserAgent()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.UserAgent) * w.Header() -> [ctx.Response.Header](https://pkg.go.dev/github.com/valyala/fasthttp#ResponseHeader) * w.Header().Set() -> [ctx.Response.Header.Set()](https://pkg.go.dev/github.com/valyala/fasthttp#ResponseHeader.Set) * w.Header().Set("Content-Type") -> [ctx.SetContentType()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.SetContentType) * w.Header().Set("Set-Cookie") -> [ctx.Response.Header.SetCookie()](https://pkg.go.dev/github.com/valyala/fasthttp#ResponseHeader.SetCookie) * w.Write() -> [ctx.Write()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Write), [ctx.SetBody()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.SetBody), [ctx.SetBodyStream()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.SetBodyStream), [ctx.SetBodyStreamWriter()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.SetBodyStreamWriter) * w.WriteHeader() -> [ctx.SetStatusCode()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.SetStatusCode) * w.(http.Hijacker).Hijack() -> [ctx.Hijack()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Hijack) * http.Error() -> [ctx.Error()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Error) * http.FileServer() -> [fasthttp.FSHandler()](https://pkg.go.dev/github.com/valyala/fasthttp#FSHandler), [fasthttp.FS](https://pkg.go.dev/github.com/valyala/fasthttp#FS) * http.ServeFile() -> [fasthttp.ServeFile()](https://pkg.go.dev/github.com/valyala/fasthttp#ServeFile) * http.Redirect() -> [ctx.Redirect()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Redirect) * http.NotFound() -> [ctx.NotFound()](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.NotFound) * http.StripPrefix() -> [fasthttp.PathRewriteFunc](https://pkg.go.dev/github.com/valyala/fasthttp#PathRewriteFunc) * *VERY IMPORTANT!* Fasthttp disallows holding references to [RequestCtx](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx) or to its' members after returning from [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler). Otherwise [data races](http://go.dev/blog/race-detector) are inevitable. Carefully inspect all the net/http request handlers converted to fasthttp whether they retain references to RequestCtx or to its' members after returning. RequestCtx provides the following _band aids_ for this case: * Wrap RequestHandler into [TimeoutHandler](https://pkg.go.dev/github.com/valyala/fasthttp#TimeoutHandler). * Call [TimeoutError](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.TimeoutError) before returning from RequestHandler if there are references to RequestCtx or to its' members. See [the example](https://pkg.go.dev/github.com/valyala/fasthttp#example-RequestCtx-TimeoutError) for more details. Use this brilliant tool - [race detector](http://go.dev/blog/race-detector) - for detecting and eliminating data races in your program. If you detected data race related to fasthttp in your program, then there is high probability you forgot calling [TimeoutError](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.TimeoutError) before returning from [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler). * Blind switching from net/http to fasthttp won't give you performance boost. While fasthttp is optimized for speed, its' performance may be easily saturated by slow [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler). So [profile](http://go.dev/blog/pprof) and optimize your code after switching to fasthttp. For instance, use [quicktemplate](https://github.com/valyala/quicktemplate) instead of [html/template](https://pkg.go.dev/html/template). * See also [fasthttputil](https://pkg.go.dev/github.com/valyala/fasthttp/fasthttputil), [fasthttpadaptor](https://pkg.go.dev/github.com/valyala/fasthttp/fasthttpadaptor) and [expvarhandler](https://pkg.go.dev/github.com/valyala/fasthttp/expvarhandler). ## Performance optimization tips for multi-core systems * Use [reuseport](https://pkg.go.dev/github.com/valyala/fasthttp/reuseport) listener. * Run a separate server instance per CPU core with GOMAXPROCS=1. * Pin each server instance to a separate CPU core using [taskset](http://linux.die.net/man/1/taskset). * Ensure the interrupts of multiqueue network card are evenly distributed between CPU cores. See [this article](https://blog.cloudflare.com/how-to-achieve-low-latency/) for details. * Use the latest version of Go as each version contains performance improvements. ## Fasthttp best practices * Do not allocate objects and `[]byte` buffers - just reuse them as much as possible. Fasthttp API design encourages this. * [sync.Pool](https://pkg.go.dev/sync#Pool) is your best friend. * [Profile your program](http://go.dev/blog/pprof) in production. `go tool pprof --alloc_objects your-program mem.pprof` usually gives better insights for optimization opportunities than `go tool pprof your-program cpu.pprof`. * Write [tests and benchmarks](https://pkg.go.dev/testing) for hot paths. * Avoid conversion between `[]byte` and `string`, since this may result in memory allocation+copy. Fasthttp API provides functions for both `[]byte` and `string` - use these functions instead of converting manually between `[]byte` and `string`. There are some exceptions - see [this wiki page](https://github.com/golang/go/wiki/CompilerOptimizations#string-and-byte) for more details. * Verify your tests and production code under [race detector](https://go.dev/doc/articles/race_detector.html) on a regular basis. * Prefer [quicktemplate](https://github.com/valyala/quicktemplate) instead of [html/template](https://pkg.go.dev/html/template) in your webserver. ## Tricks with `[]byte` buffers The following tricks are used by fasthttp. Use them in your code too. * Standard Go functions accept nil buffers ```go var ( // both buffers are uninitialized dst []byte src []byte ) dst = append(dst, src...) // is legal if dst is nil and/or src is nil copy(dst, src) // is legal if dst is nil and/or src is nil (string(src) == "") // is true if src is nil (len(src) == 0) // is true if src is nil src = src[:0] // works like a charm with nil src // this for loop doesn't panic if src is nil for i, ch := range src { doSomething(i, ch) } ``` So throw away nil checks for `[]byte` buffers from you code. For example, ```go srcLen := 0 if src != nil { srcLen = len(src) } ``` becomes ```go srcLen := len(src) ``` * String may be appended to `[]byte` buffer with `append` ```go dst = append(dst, "foobar"...) ``` * `[]byte` buffer may be extended to its' capacity. ```go buf := make([]byte, 100) a := buf[:10] // len(a) == 10, cap(a) == 100. b := a[:100] // is valid, since cap(a) == 100. ``` * All fasthttp functions accept nil `[]byte` buffer ```go statusCode, body, err := fasthttp.Get(nil, "http://google.com/") uintBuf := fasthttp.AppendUint(nil, 1234) ``` * String and `[]byte` buffers may converted without memory allocations ```go func b2s(b []byte) string { return *(*string)(unsafe.Pointer(&b)) } func s2b(s string) (b []byte) { bh := (*reflect.SliceHeader)(unsafe.Pointer(&b)) sh := (*reflect.StringHeader)(unsafe.Pointer(&s)) bh.Data = sh.Data bh.Cap = sh.Len bh.Len = sh.Len return b } ``` ### Warning: This is an **unsafe** way, the result string and `[]byte` buffer share the same bytes. **Please make sure not to modify the bytes in the `[]byte` buffer if the string still survives!** ## Related projects * [fasthttp](https://github.com/fasthttp) - various useful helpers for projects based on fasthttp. * [fasthttp-routing](https://github.com/qiangxue/fasthttp-routing) - fast and powerful routing package for fasthttp servers. * [http2](https://github.com/dgrr/http2) - HTTP/2 implementation for fasthttp. * [router](https://github.com/fasthttp/router) - a high performance fasthttp request router that scales well. * [fastws](https://github.com/fasthttp/fastws) - Bloatless WebSocket package made for fasthttp to handle Read/Write operations concurrently. * [gramework](https://github.com/gramework/gramework) - a web framework made by one of fasthttp maintainers * [lu](https://github.com/vincentLiuxiang/lu) - a high performance go middleware web framework which is based on fasthttp. * [websocket](https://github.com/fasthttp/websocket) - Gorilla-based websocket implementation for fasthttp. * [websocket](https://github.com/dgrr/websocket) - Event-based high-performance WebSocket library for zero-allocation websocket servers and clients. * [fasthttpsession](https://github.com/phachon/fasthttpsession) - a fast and powerful session package for fasthttp servers. * [atreugo](https://github.com/savsgio/atreugo) - High performance and extensible micro web framework with zero memory allocations in hot paths. * [kratgo](https://github.com/savsgio/kratgo) - Simple, lightweight and ultra-fast HTTP Cache to speed up your websites. * [kit-plugins](https://github.com/wencan/kit-plugins/tree/master/transport/fasthttp) - go-kit transport implementation for fasthttp. * [Fiber](https://github.com/gofiber/fiber) - An Expressjs inspired web framework running on Fasthttp * [Gearbox](https://github.com/gogearbox/gearbox) - :gear: gearbox is a web framework written in Go with a focus on high performance and memory optimization * [http2curl](https://github.com/li-jin-gou/http2curl) - A tool to convert fasthttp requests to curl command line ## FAQ * *Why creating yet another http package instead of optimizing net/http?* Because net/http API limits many optimization opportunities. For example: * net/http Request object lifetime isn't limited by request handler execution time. So the server must create a new request object per each request instead of reusing existing objects like fasthttp does. * net/http headers are stored in a `map[string][]string`. So the server must parse all the headers, convert them from `[]byte` to `string` and put them into the map before calling user-provided request handler. This all requires unnecessary memory allocations avoided by fasthttp. * net/http client API requires creating a new response object per each request. * *Why fasthttp API is incompatible with net/http?* Because net/http API limits many optimization opportunities. See the answer above for more details. Also certain net/http API parts are suboptimal for use: * Compare [net/http connection hijacking](https://pkg.go.dev/net/http#Hijacker) to [fasthttp connection hijacking](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Hijack). * Compare [net/http Request.Body reading](https://pkg.go.dev/net/http#Request) to [fasthttp request body reading](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.PostBody). * *Why fasthttp doesn't support HTTP/2.0 and WebSockets?* [HTTP/2.0 support](https://github.com/fasthttp/http2) is in progress. [WebSockets](https://github.com/fasthttp/websockets) has been done already. Third parties also may use [RequestCtx.Hijack](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.Hijack) for implementing these goodies. * *Are there known net/http advantages comparing to fasthttp?* Yes: * net/http supports [HTTP/2.0 starting from go1.6](https://pkg.go.dev/golang.org/x/net/http2). * net/http API is stable, while fasthttp API constantly evolves. * net/http handles more HTTP corner cases. * net/http can stream both request and response bodies * net/http can handle bigger bodies as it doesn't read the whole body into memory * net/http should contain less bugs, since it is used and tested by much wider audience. * *Why fasthttp API prefers returning `[]byte` instead of `string`?* Because `[]byte` to `string` conversion isn't free - it requires memory allocation and copy. Feel free wrapping returned `[]byte` result into `string()` if you prefer working with strings instead of byte slices. But be aware that this has non-zero overhead. * *Which GO versions are supported by fasthttp?* Go 1.21.x and newer. Older versions might work, but won't officially be supported. * *Please provide real benchmark data and server information* See [this issue](https://github.com/valyala/fasthttp/issues/4). * *Are there plans to add request routing to fasthttp?* There are no plans to add request routing into fasthttp. Use third-party routers and web frameworks with fasthttp support: * [fasthttp-routing](https://github.com/qiangxue/fasthttp-routing) * [router](https://github.com/fasthttp/router) * [gramework](https://github.com/gramework/gramework) * [lu](https://github.com/vincentLiuxiang/lu) * [atreugo](https://github.com/savsgio/atreugo) * [Fiber](https://github.com/gofiber/fiber) * [Gearbox](https://github.com/gogearbox/gearbox) See also [this issue](https://github.com/valyala/fasthttp/issues/9) for more info. * *I detected data race in fasthttp!* Cool! [File a bug](https://github.com/valyala/fasthttp/issues/new). But before doing this check the following in your code: * Make sure there are no references to [RequestCtx](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx) or to its' members after returning from [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler). * Make sure you call [TimeoutError](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx.TimeoutError) before returning from [RequestHandler](https://pkg.go.dev/github.com/valyala/fasthttp#RequestHandler) if there are references to [RequestCtx](https://pkg.go.dev/github.com/valyala/fasthttp#RequestCtx) or to its' members, which may be accessed by other goroutines. * *I didn't find an answer for my question here* Try exploring [these questions](https://github.com/valyala/fasthttp/issues?q=label%3Aquestion).