[Sugar-devel] [PATCH Browse] Cancel a download if space is very tight SL #394

Martin Langhoff martin.langhoff at gmail.com
Tue Sep 11 16:50:22 EDT 2012

On Tue, Sep 11, 2012 at 4:32 PM, Manuel Kaufmann <humitos at gmail.com> wrote:
> I didn't find an exception raised by Sugar when this happens. The
> check is done[1] when a new Model is created[2] or updated[3] inside
> the Journal, and if there are less than 50Mb a ModelAlert is shown but
> no exception is raised. Maybe we can write the portion of code here to
> raise that exception before show the ModelAlert and if it's not
> managed we can call the ModelAlert.
> [1] sugar/src/jarabe/journal/journalactivity.py L336
> [2] sugar/src/jarabe/journal/journalactivity.py L274
> [3] sugar/src/jarabe/journal/journalactivity.py L265

Forget about check_available_space() and pretty messages to the user.
The real problem is hitting out-of-disk space. Can you run a test that
bypasses this code so it really gets to ENOSPC?

How does ENOSPC appear in Python?
Py documentation is pretty incomplete:
This says IOError 28

I guess you'll have to try yourself. Try

mkdir /tmp/foo
sudo mount -t tmpfs -o size=1M none /tmp/foo

Now write there to a file in /tmp/foo to see what happens, exactly.

> The file is downloaded in a temporary directory and then copied to the Journal:
>  temp_path = os.path.join(activity.get_activity_root(), 'instance')
>  fd, self._dest_path = tempfile.mkstemp(dir=temp_path,
>                                     suffix=download.get_suggested_filename(),
>                                     prefix='tmp')

I guess activity.get_activity_root() is in the main FS, not in a tmpfs. Luckily.

> That is something like (I guess):
> ~/.sugar/default/org.laptop.WebActivity/instance

Ah, cool. So it's in the same FS.

> When the download finishes:
> (...)
> self.dl_jobject = datastore.create()
> (...)
> datastore.write(self.dl_jobject,
>                             transfer_ownership=True,
>                             reply_handler=self.__internal_save_cb,
>                             error_handler=self.__internal_error_cb,
>                             timeout=360)
> (...)

Oh, that expects a callback. If there is an exception, maybe we don't
get it on this side? :-(

> def __progress_change_cb(self, download, something):
>         progress = self._download.get_progress()
>         self.dl_jobject.metadata['progress'] = str(int(progress * 100))
>         datastore.write(self.dl_jobject)
> so, we are updating a model inside the datastore... If we had the
> ENOSPC exception we could manage it there. I insist this goes in a
> different ticket and a different patch.

Being  callback, its is probably going over dbus, so, ummm.

 martin.langhoff at gmail.com
 martin at laptop.org -- Software Architect - OLPC
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first
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