go - 为什么 io.Copy 会引发 NetworkIdleTimeout 错误?
问题描述
请考虑下面的可运行示例。
package main
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/tls"
"crypto/x509"
"encoding/pem"
"io"
"log"
"math/big"
"time"
quic "github.com/lucas-clemente/quic-go"
)
// var qc = &quic.Config{Versions: []quic.VersionNumber{101}}
var qc *quic.Config
// GenerateTLSConfig creates bare-bones TLS config for the server
func GenerateTLSConfig() *tls.Config {
key, err := rsa.GenerateKey(rand.Reader, 1024)
if err != nil {
panic(err)
}
// generate a random serial number (a real cert authority would have some logic behind this)
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
panic("failed to generate serial number: " + err.Error())
}
template := x509.Certificate{
SerialNumber: serialNumber,
// DNSNames: []string{"localhost"}, // keep mint happy
NotBefore: time.Now(),
NotAfter: time.Now().Add(time.Hour * 87600), // in 10 years
BasicConstraintsValid: true,
}
certDER, err := x509.CreateCertificate(rand.Reader, &template, &template, &key.PublicKey, key)
if err != nil {
panic(err)
}
keyPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)})
certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER})
tlsCert, err := tls.X509KeyPair(certPEM, keyPEM)
if err != nil {
panic(err)
}
return &tls.Config{
Certificates: []tls.Certificate{tlsCert},
InsecureSkipVerify: true,
}
}
func server() (quic.Listener, error) {
return quic.ListenAddr("localhost:9001", GenerateTLSConfig(), qc)
}
func accept(l quic.Listener) (quic.Session, error) {
return l.Accept()
}
func acceptStream(sess quic.Session) (quic.Stream, error) {
return sess.AcceptStream()
}
func client() (quic.Session, error) {
return quic.DialAddr("localhost:9001", GenerateTLSConfig(), qc)
}
func openStream(sess quic.Session) (quic.Stream, error) {
return sess.OpenStreamSync()
}
func main() {
ch := make(chan struct{})
go func() {
l, err := server()
if err != nil {
log.Fatal("failed to listen:", err)
}
sess, err := accept(l)
if err != nil {
log.Fatal("failed to accept session:", err)
}
s, err := acceptStream(sess)
if err != nil {
log.Fatal("failed to accept stream:", err)
}
log.Println("stream accepted")
// b := make([]byte, len("hello, world"))
// if _, err = s.Read(b); err != nil {
// log.Fatal("failed to read from stream:", err)
// }
// log.Println(string(b))
buf := bytes.NewBuffer(make([]byte, len("hello, world")))
if _, err = io.Copy(buf, s); err != nil {
log.Fatal("failed to read from stream:", err)
}
log.Println(buf.String())
close(ch)
}()
sess, err := client()
if err != nil {
log.Fatal("failed to dial:", err)
}
s, err := openStream(sess)
if err != nil {
log.Fatal("failed to open stream:", err)
}
log.Print("writing")
if _, err = io.Copy(s, bytes.NewBuffer([]byte("hello, world"))); err != nil {
log.Fatal("failed to write:", err)
}
log.Print("wrote")
<-ch
}
运行此示例将产生以下输出:
$ go run cmd/scratch/main.go (656ms)
2018/05/19 13:09:17 writing
2018/05/19 13:09:17 wrote
2018/05/19 13:09:17 stream accepted
2018/05/19 13:09:47 failed to read from stream:NetworkIdleTimeout: No recent network activity.
exit status 1
改变
buf := bytes.NewBuffer(make([]byte, len("hello, world")))
if _, err = io.Copy(buf, s); err != nil {
log.Fatal("failed to read from stream:", err)
}
log.Println(buf.String())
至
b := make([]byte, len("hello, world"))
if _, err = s.Read(b); err != nil {
log.Fatal("failed to read from stream:", err)
}
log.Println(string(b))
似乎解决了这个问题。
问题:
在这种情况下,为什么不io.Copy
与bytes.Buffer
作品一起使用?
解决方案
这与您使用bytes.Buffer
. 相反,io.Copy
等待EOF。Read
只是读取当前的内容。如果您的流从未关闭,io.Copy
则永远不会结束。
这意味着,在其他条件相同的情况下,无论您使用io.Copy
还是-- 您Read
可能不会在使用 时注意到它Read
,因为Read
立即返回,并且超时仅在 30 秒后发生。
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