如何提供Blobstorage图片的大型zip文件？

Question

I want to serve a dynamic zip file with multiple user uploaded images that are stored in blobstorage

I'm successfuly doing it with the following code, but I encounter a problem where the Appengine instances are being terminated because they consume too much memory.

is it possible to serve such zip files by streaming them directly to the client and not keeping them in the memory? is there another solution?

w.Header().Set("Content-Type", "application/zip")
w.Header().Set("Content-Disposition", "attachment;filename=photos.zip")

writer := zip.NewWriter(w)

defer writer.Close()

for _, key := range l.Files {
    info, err := blobstore.Stat(c, appengine.BlobKey(key))

    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return  
    }

    wr, err := writer.Create(info.Filename)

    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return  
    }

    reader := blobstore.NewReader(c, appengine.BlobKey(key))

    io.Copy(wr, reader)
}   

Answer 1

You should probably create the zip file in the blobstore, then serve it from there:

• Create the zip in the blobstore utilizing blobstore.Writer
• Serve the zip using blobstore.Send

This way you can also speed up subsequent requests for the same zip/bundle as you will have already created/stored it.