go lang http 处理程序中的内存泄漏

Question

我有以下 http 处理程序代码，根据后续请求，它根据 Amazon S3 下载原始图像并将其转换为所需的纵横比并将其保存回 s3。此代码泄漏内存，一段时间后崩溃。我已经从我这边处理了所有事情，并对代码进行了分析。但是，仍然无法弄清楚问题所在。如果有人能在这里弄清楚，将不胜感激。仅供参考，我使用的是go version go1.5.3 linux/amd64版本.

分析输出：

3259.27kB of 3302.42kB total (98.69%)
Dropped 258 nodes (cum <= 16.51kB)
Showing top 30 nodes out of 91 (cum >= 27.76kB)
      flat  flat%   sum%        cum   cum%
 1552.59kB 47.01% 47.01%  1552.59kB 47.01%  bytes.makeSlice
     584kB 17.68% 64.70%      584kB 17.68%  imagick._Cfunc_GoBytes
  257.38kB  7.79% 72.49%   257.38kB  7.79%  encoding/pem.Decode
  168.11kB  5.09% 77.58%   168.11kB  5.09%  crypto/tls.(*block).reserve
  165.09kB  5.00% 82.58%   389.49kB 11.79%  crypto/x509.parseCertificate
  105.32kB  3.19% 85.77%   105.32kB  3.19%  reflect.unsafe_NewArray
   83.64kB  2.53% 88.30%    83.64kB  2.53%  math/big.nat.make
   75.55kB  2.29% 90.59%    75.55kB  2.29%  net/http.(*Transport).dialConn
   64.02kB  1.94% 92.53%    64.02kB  1.94%  regexp.(*bitState).reset
   43.77kB  1.33% 93.85%    43.77kB  1.33%  crypto/x509.(*CertPool).AddCert
   40.44kB  1.22% 95.08%    40.44kB  1.22%  crypto/x509/pkix.(*Name).FillFromRDNSequence
   40.16kB  1.22% 96.29%    40.16kB  1.22%  encoding/asn1.parsePrintableString
   24.07kB  0.73% 97.02%    24.07kB  0.73%  net/http.newBufioWriterSize
   18.98kB  0.57% 97.60%    18.98kB  0.57%  net/http.newBufioReader
   16.14kB  0.49% 98.09%    64.77kB  1.96%  crypto/tls.(*Conn).readHandshake
   12.01kB  0.36% 98.45%   237.09kB  7.18%  encoding/asn1.parseField
    8.01kB  0.24% 98.69%    91.65kB  2.78%  crypto/x509.parsePublicKey
         0     0% 98.69%   112.33kB  3.40%  bufio.(*Reader).Read
         0     0% 98.69%    80.32kB  2.43%  bufio.(*Reader).fill
         0     0% 98.69%    27.76kB  0.84%  bufio.(*Writer).ReadFrom
         0     0% 98.69%    27.76kB  0.84%  bufio.(*Writer).flush
         0     0% 98.69%  1648.33kB 49.91%  bytes.(*Buffer).ReadFrom
         0     0% 98.69%    16.59kB   0.5%  bytes.(*Buffer).Write
         0     0% 98.69%    16.59kB   0.5%  bytes.(*Buffer).grow
         0     0% 98.69%   843.06kB 25.53%  crypto/tls.(*Conn).Handshake
         0     0% 98.69%   112.33kB  3.40%  crypto/tls.(*Conn).Read
         0     0% 98.69%    27.76kB  0.84%  crypto/tls.(*Conn).Write
         0     0% 98.69%   843.06kB 25.53%  crypto/tls.(*Conn).clientHandshake
         0     0% 98.69%   160.96kB  4.87%  crypto/tls.(*Conn).readRecord
         0     0% 98.69%    27.76kB  0.84%  crypto/tls.(*Conn).writeRecord

法典：

func main() {       
    imagick.Initialize() 
    defer imagick.Terminate()   
        myMux := http.NewServeMux()
        myMux.HandleFunc("/", serveHTTP)       
      if err := http.ListenAndServe(":8082", myMux); err != nil {
        logFatal("Error when starting or running http server: %v", err)
    }      
}
func serveHTTP(w http.ResponseWriter, r *http.Request) {
        var isMaster bool = true        
    var desiredAspectRatio float64 = 1.77   
    if r.RequestURI == "/favicon.ico" {
        w.WriteHeader(http.StatusNotFound)
        return
    }
    if len(strings.TrimSpace(r.URL.Query().Get("ar"))) != 0 {
        desiredAspectRatio, _ = strconv.ParseFloat(r.URL.Query().Get("ar"), 64)
    }
    if len(strings.TrimSpace(r.URL.Query().Get("ism"))) != 0 {      
        isMaster, _ = strconv.ParseBool(r.URL.Query().Get("ism"))
    }   
    imageUrl := strings.ToLower(r.URL.Path[1:])     
    isProcessed := CreateMaster(imageUrl, desiredAspectRatio, isMaster)     
    if isProcessed == false {
        w.WriteHeader(http.StatusNotFound) 
        return
    }
    if !sendResponse(w, r, imageUrl) {
        // w.WriteHeader() is skipped intentionally here, since the response may be already partially created.
        return
    }

    logRequestMessage(r, "SUCCESS")     
}

func sendResponse(w http.ResponseWriter, r *http.Request, imageUrl string) bool {
    w.Header().Set("Content-Type", "text/plain")        
    if _, err := w.Write([]byte("master created")); err != nil {
        logRequestError(r, "Cannot send image from imageUrl=%v to client: %v", imageUrl, err)
        return false
    }
    return true
}

func CreateMaster(keyName string, desiredAspectRatio float64, isMaster bool) bool {             
    s3Client := s3.New(session.New(), &aws.Config{Region: aws.String(region)})
        params := &s3.GetObjectInput{
        Bucket: aws.String(bucketName),
        Key: aws.String(keyName),
        }
    fmt.Println(" Master creation request for key : " + keyName)
    out, err := s3Client.GetObject(params)
    if err != nil { 
        return false                                       
    }
    defer out.Body.Close()  
    img, err := ioutil.ReadAll(out.Body)
    if err != nil { 
            return false      
    }                   
    mw := imagick.NewMagickWand()
    defer mw.Destroy()
    err = mw.ReadImageBlob(img)
    if err != nil {  
        return false                   
    }

    if isMaster == false {
        paramsPut := &s3.PutObjectInput{
                    Bucket:         aws.String(masterBucketName),
                    Key:            aws.String(keyName),
                    Body:         bytes.NewReader(mw.GetImageBlob()),
            }
        _, err = s3Client.PutObject(paramsPut)
        if err != nil {
            log.Printf("Couldn't put the image on s3 : " + keyName + "%sn", err)       
        }
        return true
    }

        originalWidth := float64(mw.GetImageWidth())
        originalHeight := float64(mw.GetImageHeight())
    imageAspectRatio  := originalWidth / originalHeight
        masterWidth := cwMasterWidth
        masterHeight := cwMasterHeight
        masterAspectRatio := math.Trunc((cwMasterWidth / cwMasterHeight) * 100)/100
    if masterAspectRatio != desiredAspectRatio {           
                    masterAspectRatio = desiredAspectRatio
                }

    pwm := imagick.NewPixelWand()
    defer pwm.Destroy()
    tx := imagick.NewMagickWand()
    defer tx.Destroy()  
    if isMaster == true {               
            var w, h uint = 0, 0
            size := fmt.Sprintf("%dx%d^+0+0", w, h) 
                    if imageAspectRatio <= masterAspectRatio {                
                        // trim the height
            w = uint(originalWidth)
            h = (uint(originalWidth / masterAspectRatio))
               size = fmt.Sprintf("%dx%d^+0+0", w, h)
                     } else { 
                        // trim the width
            w = uint(originalHeight * masterAspectRatio)
            h = uint(originalHeight)
            size = fmt.Sprintf("%dx%d^+0+0", w, h)
                     }
            tx = mw.TransformImage("", size)        
            tx.SetImageGravity(imagick.GRAVITY_CENTER)
            offsetX := -(int(w) - int(tx.GetImageWidth())) / 2
            offsetY := -(int(h) - int(tx.GetImageHeight())) / 2
            err := tx.ExtentImage(w, h, offsetX, offsetY)
                    if float64(tx.GetImageWidth()) > masterWidth && float64(tx.GetImageHeight()) > masterHeight  {                                        
                        err = tx.ResizeImage(uint(masterWidth), uint(masterHeight), imagick.FILTER_BOX, 1)
            if err != nil {
                log.Printf("Inside CreateMaster function Couldn't resize the image : " + keyName + "%sn", err) 
                return false                 
            }                                                           
                    }                                       
                }       
     paramsPut := &s3.PutObjectInput{
                    Bucket:         aws.String(masterBucketName),
                    Key:            aws.String(keyName),
                    Body:         bytes.NewReader(tx.GetImageBlob()),
            }
    _, err = s3Client.PutObject(paramsPut)
    if err != nil {
        log.Printf("Inside CreateMaster function Couldn't put the image on s3 : " + keyName + "%sn", err)  
        return false        
    }
    return true
}

Answer 1

你在漏一根魔杖。

在这里，您分配一根新魔杖并推迟它进行销毁：

tx := imagick.NewMagickWand()
defer tx.Destroy()  

但再往下，在"if"块中，你用调用TransformImage()返回的魔杖替换它：

        tx = mw.TransformImage("", size)        
        tx.SetImageGravity(imagick.GRAVITY_CENTER)

如果您完全摆脱了新魔杖的第一个分配，并且只需确保Destroy()从TransformImage()返回的新魔杖，泄漏就会消失。

有关详细信息，请参阅问题跟踪器#72