修复并发上传时程序崩溃的问题

这个是我复现时用来压力测试的Go代码，如果把zimg log level开到7，应该很容易复现，6的话可能要多试两次。
package main

import (
    "bytes"
    "fmt"
    "net/http"
    "strings"
    "sync"
    "time"
)

var count int = 0
var lock sync.Mutex

func post(index int) {
    image1 := []byte{
        0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49, 0x48, 0x44, 0x52,
        0x00, 0x00, 0x00, 0x24, 0x00, 0x00, 0x00, 0x24, 0x08, 0x06, 0x00, 0x00, 0x00, 0xE1, 0x00, 0x98,
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        0xFA, 0x61, 0x89, 0x44, 0x5A, 0xB5, 0x44, 0x04, 0xEB, 0xEB, 0x43, 0xED, 0x83, 0x60, 0xAB, 0xA2,
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        0x4E, 0x44, 0xAE, 0x42, 0x60, 0x82}
    image2 := []byte{
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        0xD0, 0xD0, 0x90, 0x28, 0x4B, 0x29, 0xB2, 0x18, 0xDD, 0xF2, 0xFC, 0xC2, 0x42, 0x06, 0x61, 0x21,
        0x21, 0x06, 0x2F, 0x4F, 0x4F, 0x82, 0x96, 0x52, 0x6C, 0x31, 0xB2, 0xE5, 0xBF, 0x7E, 0xFD, 0x22,
        0xDA, 0x52, 0xAA, 0x58, 0x0C, 0xB3, 0xFC, 0xD3, 0xC7, 0x8F, 0x44, 0x5B, 0x4A, 0x35, 0x8B, 0xC9,
        0x01, 0x23, 0xCF, 0x62, 0x00, 0x78, 0x04, 0x2C, 0x2E, 0xD8, 0x80, 0x5F, 0xD5, 0x00, 0x00, 0x00,
        0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE, 0x42, 0x60, 0x82}
    var buffer *bytes.Buffer
    var size string
    if (index & 1) > 0 {
        buffer = bytes.NewBuffer(image1)
        size = "1446"
    } else {
        buffer = bytes.NewBuffer(image2)
        size = "409"
    }
    req, err := http.NewRequest("POST", "http://192.168.1.200:4869/upload", buffer)
    if err != nil {
        fmt.Println(err)
        lock.Lock()
        count++
        lock.Unlock()
        return
    }
    req.Header.Add("Content-Type", "png")
    req.Header.Add("Content-Length", size)
    var client http.Client
    resp, err := client.Do(req)
    if err != nil {
        lock.Lock()
        count++
        lock.Unlock()
        return
    }
    defer resp.Body.Close()
    length := int(resp.ContentLength)
    if length > 1024 {
        fmt.Println("Content too long")
        lock.Lock()
        count++
        lock.Unlock()
        return
    }
    data := make([]byte, length)
    offset := 0
    for offset < length {
        read, err := resp.Body.Read(data[offset:])
        if err != nil {
            if !strings.Contains(err.Error(), "EOF") {
                fmt.Println(err)
                lock.Lock()
                count++
                lock.Unlock()
                return
            }
        }
        offset += read
    }
    fmt.Println(fmt.Sprintf("%d: %s", index, string(data)))
    lock.Lock()
    count++
    lock.Unlock()
}

func main() {
    for idx := 0; idx < 100000; idx++ {
        go post(idx)
    }
    last1 := 0
    last2 := 0
    for count < 100000 {
        time.Sleep(time.Second)
        last1 = count
        if last2 != last1 {
            fmt.Println(fmt.Sprintf("%d finished.", count))
            last2 = last1
        }
    }
    fmt.Println("All HTTP POST finished!")
}
buaazp / zimg

修复并发上传时程序崩溃的问题 #170
