Too many requests after uploading an image to google cloud storage - google-app-engine

Question

I watch a gcs bucket with watchbucket command. After that i am doing a upload. The watch command sends a notification to my servlet on app engine.
To be sure about that, i have a look at the logs. But it seems so, that some how the servlet keeps on getting request after request. Four times successfully and after that it gets an nullpointer exception. Why are there so many requests?
* EDIT *
On client side i use a meteorJS a Javascript framework. I added the extension slingshot to process the upload.
first i have to provide a the necessary info like acl, bucket, etc. like this:
Slingshot.createDirective('uploadSpotCover', Slingshot.GoogleCloud, {
bucket: 'upload_spot_cover',
GoogleAccessId: 'accessId',
acl: 'project-private',
maxSize: 0,
cacheControl: 'no-cache',
...
}
As you can see in line 153 slingshot uses a XMLHttpRequest to upload to Cloudstorage
https://github.com/CulturalMe/meteor-slingshot/blob/master/lib/upload.js#L144
On serverside my Servlet and it's logic look like this.
public class Upload extends HttpServlet {
private BucketNotification notification;
#Override
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
this.notification = getBucketNotification(req);
UploadObject object = new UploadObject(notification);
CloudStorageHandler gcs = new CloudStorageHandler();
BlobstoreHandler bs = new BlobstoreHandler();
ImageTransformHandler is = new ImageTransformHandler();
/** GET DATA FROM GCS **/
byte[] data = gcs.getFileFromGoogleCloudStorage(object.getGcsBucket(), object.getGcsPath());
//BlobKey bk = bs.createBlobKey(object.getGcsBucket(), object.getGcsPath());
/******************/
/** TRANSFORMATION **/
byte[] newImageData = is.resizePicture(data, 1200, 1200, "JPEG", 65, 0.5, 0.5);
/******************/
/** STORE NEW RESIZED FILE INTO GCS BUCKET **/
UploadObject tmp = new UploadObject(object.getGcsPath(), "JPEG", "beispiel", 1200, 1200);
tmp.setData(newImageData);
gcs.saveFileToGoogleCloudStorage(newImageData, "beispiel", object.getGcsPath(), "JPEG", "public-read");
/******************/
/** CREATE SERVING URL via BLOBKEY **/
BlobKey bk_neu = bs.createBlobKey("beispiel", object.getGcsPath());
String servingUrl = is.createServingUrlWithBlobkey(bk_neu);
/******************/
log("Blobkey: "+ bk_neu.getKeyString());
log("url: "+ servingUrl);
res.setStatus(200);
}
private BucketNotification getBucketNotification(HttpServletRequest req) {
BucketNotification notification = null;
String jsonString ="";
try {
jsonString ="";
BufferedReader in = new BufferedReader(new InputStreamReader(req.getInputStream()));
for (String buffer;(buffer = in.readLine()) != null;jsonString+=buffer + "\n");
in.close();
notification = new Gson().fromJson(jsonString, BucketNotification.class);
} catch (IOException e) {
log("Failed to decode the notification: " + e.getMessage());
return null;
}
return notification;
}
}
I wrapped the specific service methods like save file to cloudstorage in its own handlers.

Answer 1

Because I do not know what you are using to upload, I'm guessing now. Most file uploads upload stuff in bulks, so not the whole file at once, but in smaller chunks until everything is up. This would explain the multiple calls you are getting.
Can you show us the server and the client code? Maybe that way we could see the problem.