Similar to #966

Celery 3.2 or 4.0 or whatever it becomes hasn't been released yet, but Ask is planning on dropping Python 2.6

See the note on dropped 2.5 support ​here

This is more of an FYI than an actual bug.

When Celery is starting or after it has run for a few minutes I get many "connection reset" errors in the log.

After this errors Celery does not recover and appears to be running but does not process any tasks.

There are two root causes for this problem:

1) The systemd service file provided as example in the deployment guide does not specify that celery must be started after RabbitMQ. The OS is free to start them in any order and when celery starts before RabbitMQ it will not be able to connect

2) In mediagoblin/init/celery/init.py the BROKER_HEARTBEAT is set to 1 second. In slower machines or under heavy load this setting causes missed hearbeats and a eventual connection reset. I think this code had the intention to cause a more granular task scheduling but from what I understand from celery docs it has nothing to do with task scheduling. The CELERYBEAT_SCHEDULE is just a periodic task and has nothing to do with BROKER_HEARTBEAT.

The docs say that audiolab is for spectrograms. I don't think this should be a critical feature for audio uploading and transcoding to work. It is possible that I'm missing something and audiolab is more important than I thought though. When I upload a flac file without audiolab installed I get the following error:

2013-04-03 22:11:30,136 ERROR   [celery] Task mediagoblin.processing.task.ProcessMedia[c1ac8460-95b5-44bc-bc5d-f02a9204be1b] raised exception: NameError("global name 'audiolab' is not defined",)
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/celery/execute/trace.py", line 181, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/share/mediagoblin/mediagoblin/processing/task.py", line 92, in run
    entry.media_manager['processor'](proc_state)
  File "/usr/share/mediagoblin/mediagoblin/media_types/audio/processing.py", line 122, in process_audio
    fft_size=audio_config['spectrogram_fft_size'])
  File "/usr/share/mediagoblin/mediagoblin/media_types/audio/transcoders.py", line 76, in spectrogram  
    numpy.hanning)
  File "/usr/share/mediagoblin/mediagoblin/media_types/audio/audioprocessing.py", line 109, in __init__
    max_level = get_max_level(input_filename)
  File "/usr/share/mediagoblin/mediagoblin/media_types/audio/audioprocessing.py", line 79, in get_max_level
    audio_file = audiolab.Sndfile(filename, 'r')
NameError: global name 'audiolab' is not defined