App Engine：API调用文件。Create（）花费的时间太长，因此已被取消

Question

When I try to write to blobstore using the same example provided in the docs (below), it works every time on dev server, but fails 100% of the time on appspot with this error: The API call file.Create() took too long to respond and was cancelled. Googling show that this is a rare issue although some have reported it. Any idea what's going on here?

I'm using Python 2.6 on dev server so that maybe why I'm not seeing this during dev.

from __future__ import with_statement
from google.appengine.api import files

# Create the file
file_name = files.blobstore.create(mime_type='application/octet-stream')

# Open the file and write to it
with files.open(file_name, 'a') as f:
  f.write('data')

# Finalize the file. Do this before attempting to read it.
files.finalize(file_name)

# Get the file's blob key
blob_key = files.blobstore.get_blob_key(file_name)

Traceback:

The API call file.Create() took too long to respond and was cancelled.
Traceback (most recent call last):
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1516, in __call__
    rv = self.handle_exception(request, response, e)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1510, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1258, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1082, in __call__
    return handler.dispatch()
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 552, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 550, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/main.py", line 43, in get
    file_name = files.blobstore.create(mime_type='text/html')
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/blobstore.py", line 69, in create
    return files._create(_BLOBSTORE_FILESYSTEM, params=params)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 491, in _create
    _make_call('Create', request, response)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 234, in _make_call
    rpc.check_success()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 558, in check_success
    self.__rpc.CheckSuccess()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_rpc.py", line 133, in CheckSuccess
    raise self.exception
DeadlineExceededError: The API call file.Create() took too long to respond and was cancelled.
Saved; key: __appstats__:082400, part: 41 bytes, full: 5691 bytes, overhead: 0.000 + 0.004; link: http://czongae.appspot.com/_ah/stats/details?time=1328696282404
<class 'google.appengine.runtime.apiproxy_errors.DeadlineExceededError'>: The API call file.Create() took too long to respond and was cancelled.
Traceback (most recent call last):
  File "/base/data/home/apps/s~czongae/1.356669185377832769/main.py", line 72, in <module>
    main()
  File "/base/data/home/apps/s~czongae/1.356669185377832769/main.py", line 69, in main
    app.run()
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1595, in run
    _webapp_util.run_wsgi_app(self)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/util.py", line 98, in run_wsgi_app
    run_bare_wsgi_app(add_wsgi_middleware(application))
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/util.py", line 118, in run_bare_wsgi_app
    for data in result:
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/appstats/recording.py", line 924, in appstats_wsgi_wrapper
    result = app(environ, appstats_start_response)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1524, in __call__
    response = self._internal_error(e)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1516, in __call__
    rv = self.handle_exception(request, response, e)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1510, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1258, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 1082, in __call__
    return handler.dispatch()
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 552, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/webapp2.py", line 550, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/apps/s~czongae/1.356669185377832769/main.py", line 43, in get
    file_name = files.blobstore.create(mime_type='text/html')
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/blobstore.py", line 69, in create
    return files._create(_BLOBSTORE_FILESYSTEM, params=params)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 491, in _create
    _make_call('Create', request, response)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 234, in _make_call
    rpc.check_success()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 558, in check_success
    self.__rpc.CheckSuccess()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_rpc.py", line 133, in CheckSuccess
    raise self.exception

Answer 1

It's not documented to the official manual. but try to add exclusive_lock=True when you open the file. During the migration of my blobstore from M/S to HRD I think I had this problem.

http://code.google.com/p/googleappengine/source/browse/trunk/python/google/appengine/api/files/file.py#402

# Open the file and write to it
with files.open(file_name, 'a', exclusive_lock=True) as f:
  f.write('data')