CODEWITHSUNDEEP
pythonimagegoogle-app-enginegoogle-cloud-storage
Micha El
Micha El

Reputation: 41

TransformationError Reasons get_serving_url / Images API

I'm running into the following error using get_serving_url in order to serve images from my bucket.

Traceback (most recent call last):
 File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
   return method(*args, **kwargs)
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/tasklets.py", line 1087, in synctasklet_wrapper
   return taskletfunc(*args, **kwds).get_result()
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/tasklets.py", line 1057, in tasklet_wrapper
   result = func(*args, **kwds)
 File "/base/data/home/apps/e~tileserve20171207t210519.406056180994857717/blob_upload.py", line 70, in post
   bf.put_async()
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/model.py", line 3473, in _put_async
   self._pre_put_hook()
 File "/base/data/home/apps/e~tileserve/20171207t210519.406056180994857717/blob_files.py", line 124, in _pre_put_hook
   print images.get_serving_url(None, filename='/gs' + '/tileserve.appspot.com/user2test4test4RGB20170927.tif')
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/images/__init__.py", line 1868, in get_serving_url
   return rpc.get_result()
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 613, in get_result
   return self.__get_result_hook(self)
 File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/images/__init__.py", line 1972, in get_serving_url_hook
   raise _ToImagesError(e, readable_blob_key)
 TransformationError

When I upload an image to my bucket then it works but when I create an image through processing which should be exposed through get_serving_url I get TransformationError.

I tried two variants for serving images:

test = blobstore.create_gs_key('/gs' + '/path2object')
images.get_serving_url(test, secure_url=True)

images.get_serving_url(None, filename='/gs' + '/' + <bucket name>+  '/'+ <object name>)

I also set the bucket object ACM permissions and the IAM App Engine app default service account permissions (storage admin). Both variants changed nothing but are important in order to access objects of a bucket.

Did somebody experience this issue ? What could be the error? I do not understand why it works when I upload an image but not for images which are generated through processing.

Upvotes: 2

Views: 711

Answers (2)

Risheak Chauhan
Risheak Chauhan

Reputation: 71

The issue is not with the get_serving_url() method. It is how you are accessing the objects from google cloud storage bucket.

I switched the access control on my bucket from uniform to fine grained which fixed the problem for me.

Upvotes: 1

Dan Cornilescu
Dan Cornilescu

Reputation: 39824

The traceback suggests you may be trying to call images.get_serving_url() while an async operation may still be in progress.

If that op is actually saving the transformed image in GCS then it could explain the failure: get_serving_url() includes a check of the file being a valid image, which would fail with TransformationError if the file is not yet saved.

If so - you can fix the problem by either:

  • switching to the sync version of saving the image
  • waiting until saving the image completes (in case you have some other stuff to do in the meantime) - get the result of the sync call before invoking get_serving_url()
  • repeatedly trying get_serving_url() while catching TransformationError until it no longer fails that way. This is a bit risky as it can end up in an infinite loop if TransformationError is raised for reasons other than simply saving the image being incomplete.

Upvotes: 2

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