go使用http.Pusher主动推送资源来优化网站加载速度

需要注意的是,目前只有http 2.0 才支持服务器主动向浏览器推送资源。

Server Push 是什么?

 为了提高网站的打开速度,http2.0提供了很多新的特性,其中一个特性就是服务器推送。简单来讲就是当用户的浏览器和服务器在建立链接后,服务器主动将一些资源推送给浏览器并缓存起来,这样当浏览器接下来请求这些资源时就直接从缓存中读取,不会在从服务器上拉了,提升了速率。举一个例子就是:

  假如一个页面有3个资源文件    index.html,    index.css,    index.js,当浏览器请求index.html的时候,服务器不仅返回index.html的内容,同时将index.css和index.js的内容push给浏览器,当浏览器下次请求这2两个文件时就可以直接从缓存中读取了。  


gonet/http包下定义了Pusher 这个接口类型来实现服务器主动推送,http2responseWriter已经为我们实现了这个协议。

下面通过一个简单示例为演示服务器主动将www.ithome.io.js这个js推送给浏览器。


package main

import (
	"fmt"
	"log"
	"net/http"
)

const itHomeJS = `console.log("欢迎访问 IT驿站");alert("欢迎访问 IT驿站")`

const indexHTML = `<html>
<head>
	<title>Hello</title>
	<script src="/www.ithome.io.js"></script>
</head>
<body>
</body>
</html>
`

func main() {
	http.HandleFunc("/www.ithome.io.js", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, itHomeJS)
	})
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		pusher, ok := w.(http.Pusher)
		// 判断是否支持推送,
		if ok {

			if err := pusher.Push("/www.ithome.io.js", nil); err != nil {
				log.Printf("Failed to push: %v", err)
			}
		}
		fmt.Fprintf(w, indexHTML)
	})

	// 在这里需要使用 generate_cert.go 来生成证书
	// go run generate_cert.go -host localhost
	// 在文章结尾会为generate_cert.go的源代码
	// 或者直接访问 https://golang.org/src/crypto/tls/generate_cert.go
	log.Fatal(http.ListenAndServeTLS(":7072", "cert.pem", "key.pem", nil))
}


然后打开浏览器输入https://localhost:7072,因为这个证书是我们自己生成的,所有浏览器会提示非信任证书,直接忽略即可。

QQ20170725-110624.png


下面生成证书的generate_cert.go源代码,保存在main.go同一个目录下面,然后执行

go run generate_cert.go -host localhost

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build ignore

// Generate a self-signed X.509 certificate for a TLS server. Outputs to
// 'cert.pem' and 'key.pem' and will overwrite existing files.

package main

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"flag"
	"fmt"
	"log"
	"math/big"
	"net"
	"os"
	"strings"
	"time"
)

var (
	host       = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
	validFrom  = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
	validFor   = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
	isCA       = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
	rsaBits    = flag.Int("rsa-bits", 2048, "Size of RSA key to generate. Ignored if --ecdsa-curve is set")
	ecdsaCurve = flag.String("ecdsa-curve", "", "ECDSA curve to use to generate a key. Valid values are P224, P256, P384, P521")
)

func publicKey(priv interface{}) interface{} {
	switch k := priv.(type) {
	case *rsa.PrivateKey:
		return &k.PublicKey
	case *ecdsa.PrivateKey:
		return &k.PublicKey
	default:
		return nil
	}
}

func pemBlockForKey(priv interface{}) *pem.Block {
	switch k := priv.(type) {
	case *rsa.PrivateKey:
		return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)}
	case *ecdsa.PrivateKey:
		b, err := x509.MarshalECPrivateKey(k)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Unable to marshal ECDSA private key: %v", err)
			os.Exit(2)
		}
		return &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
	default:
		return nil
	}
}

func main() {
	flag.Parse()

	if len(*host) == 0 {
		log.Fatalf("Missing required --host parameter")
	}

	var priv interface{}
	var err error
	switch *ecdsaCurve {
	case "":
		priv, err = rsa.GenerateKey(rand.Reader, *rsaBits)
	case "P224":
		priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
	case "P256":
		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	case "P384":
		priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
	case "P521":
		priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
	default:
		fmt.Fprintf(os.Stderr, "Unrecognized elliptic curve: %q", *ecdsaCurve)
		os.Exit(1)
	}
	if err != nil {
		log.Fatalf("failed to generate private key: %s", err)
	}

	var notBefore time.Time
	if len(*validFrom) == 0 {
		notBefore = time.Now()
	} else {
		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
			os.Exit(1)
		}
	}

	notAfter := notBefore.Add(*validFor)

	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		log.Fatalf("failed to generate serial number: %s", err)
	}

	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"Acme Co"},
		},
		NotBefore: notBefore,
		NotAfter:  notAfter,

		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}

	hosts := strings.Split(*host, ",")
	for _, h := range hosts {
		if ip := net.ParseIP(h); ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, h)
		}
	}

	if *isCA {
		template.IsCA = true
		template.KeyUsage |= x509.KeyUsageCertSign
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
	if err != nil {
		log.Fatalf("Failed to create certificate: %s", err)
	}

	certOut, err := os.Create("cert.pem")
	if err != nil {
		log.Fatalf("failed to open cert.pem for writing: %s", err)
	}
	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
	certOut.Close()
	log.Print("written cert.pem\n")

	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		log.Print("failed to open key.pem for writing:", err)
		return
	}
	pem.Encode(keyOut, pemBlockForKey(priv))
	keyOut.Close()
	log.Print("written key.pem\n")
}

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