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valyala /fasthttp

Fast HTTP package for Go. Tuned for high performance. Zero memory allocations in hot paths. Up to 10...

12.9K Stars 1.1K Forks Last release: about 1 month ago (v1.14.0) MIT License 1.3K Commits 22 Releases

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fasthttp Build Status GoDoc Go Report Sourcegraph

FastHTTP – Fastest and reliable HTTP implementation in Go

Fast HTTP implementation for Go.

Currently fasthttp is successfully used by VertaMediain a production serving up to 200K rps from more than 1.5M concurrent keep-alive connections per physical server.

TechEmpower Benchmark round 19 results

Server Benchmarks

Client Benchmarks



Examples from docs

Code examples

Awesome fasthttp tools

Switching from net/http to fasthttp

Fasthttp best practices

Tricks with byte buffers

Related projects


HTTP server performance comparison with net/http

In short, fasthttp server is up to 10 times faster than net/http. Below are benchmark results.


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


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.


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


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


go get -u

Switching from net/http to fasthttp

Unfortunately, fasthttp doesn't provide API identical to net/http. See the FAQ for details. There is net/http -> fasthttp handler converter, 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:

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 RequestHandleraccepts only one argument - 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.
// 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) } }
// 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:
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. }

Net/http code with simple ServeMux is trivially converted to fasthttp code:

// net/http code m := &http.ServeMux{} m.HandleFunc("/foo", fooHandlerFunc) m.HandleFunc("/bar", barHandlerFunc) m.Handle("/baz", bazHandler) http.ListenAndServe(":80", m)
// 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)

VERY IMPORTANT! Fasthttp disallows holding references to RequestCtx or to its' members after returning from RequestHandler. Otherwise data races 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.
  • Call TimeoutErrorbefore returning from RequestHandler if there are references to RequestCtx or to its' members. See the examplefor more details.

Use this brilliant tool - 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 TimeoutErrorbefore returning from RequestHandler.

Performance optimization tips for multi-core systems

  • Use reuseport listener.
  • Run a separate server instance per CPU core with GOMAXPROCS=1.
  • Pin each server instance to a separate CPU core using taskset.
  • Ensure the interrupts of multiqueue network card are evenly distributed between CPU cores. See this article for details.
  • Use Go 1.13 as it provides some considerable performance improvements.

Fasthttp best practices

  • Do not allocate objects and
    buffers - just reuse them as much as possible. Fasthttp API design encourages this.
  • sync.Pool is your best friend.
  • Profile your programin 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 for hot paths.
  • Avoid conversion between
    , since this may result in memory allocation+copy. Fasthttp API provides functions for both
    • use these functions instead of converting manually between
      . There are some exceptions - see this wiki pagefor more details.
  • Verify your tests and production code underrace detector on a regular basis.
  • Prefer quicktemplate instead ofhtml/template in your webserver.

Tricks with



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


buffers from you code. For example,

go srcLen := 0 if src != nil { srcLen = len(src) }


srcLen := len(src)
  • String may be appended to


buffer with

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



go statusCode, body, err := fasthttp.Get(nil, "") uintBuf := fasthttp.AppendUint(nil, 1234)

Related projects

  • fasthttp - various useful helpers for projects based on fasthttp.
  • fasthttp-routing - fast and powerful routing package for fasthttp servers.
  • router - a high performance fasthttp request router that scales well.
  • fastws - Bloatless WebSocket package made for fasthttp to handle Read/Write operations concurrently.
  • gramework - a web framework made by one of fasthttp maintainers
  • lu - a high performance go middleware web framework which is based on fasthttp.
  • websocket - Gorilla-based websocket implementation for fasthttp.
  • fasthttpsession - a fast and powerful session package for fasthttp servers.
  • atreugo - High performance and extensible micro web framework with zero memory allocations in hot paths.
  • kratgo - Simple, lightweight and ultra-fast HTTP Cache to speed up your websites.
  • kit-plugins - go-kit transport implementation for fasthttp.
  • Fiber - An Expressjs inspired web framework running on Fasthttp
  • Gearbox - :gear: gearbox is a web framework written in Go with a focus on high performance and memory optimization


  • 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


. So the server must parse all the headers, convert them from




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 to fasthttp connection hijacking. * Compare net/http Request.Body reading to fasthttp request body reading.

  • Why fasthttp doesn't support HTTP/2.0 and WebSockets?

HTTP/2.0 support is in progress. WebSockets has been done already. Third parties also may use 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. * net/http API is stable, while fasthttp API constantly evolves. * net/http handles more HTTP corner cases. * net/http should contain less bugs, since it is used and tested by much wider audience. * net/http works on Go older than 1.5.

  • _Why fasthttp API prefers returning
    instead of





conversion isn't free - it requires memory allocation and copy. Feel free wrapping returned


result into


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?

Go1.5+. Older versions won't be supported, since their standard package miss useful functions.

NOTE: Go 1.9.7 is the oldest tested version. We recommend you to update as soon as you can. As of 1.11.3 we will drop 1.9.x support.

  • Please provide real benchmark data and server information

See this issue.

  • 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]( \* [router]( \* [gramework]( \* [lu]( \* [atreugo]( \* [Fiber]( \* [Gearbox](

See also this issue for more info.

  • I detected data race in fasthttp!

Cool! File a bug. But before doing this check the following in your code:

Make sure you call TimeoutErrorbefore returning from RequestHandlerif there are references to RequestCtxor to its' members, which may be accessed by other goroutines.

  • I didn't find an answer for my question here

Try exploring these questions.

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