1 =================

     2 pyams_zmq package

     3 =================

     4 

     5 PyAMS 'ZMQ' package can be used to build wrapper around ØMQ (or ZeroMQ) library to exchange

     6 messages following all ØMQ possible usages.

     7 

     8 At least two components are required to build a ØMQ based application:

     9 

    10 - a ØMQ server

    11 

    12 - a ØMQ client

    13 

    14 The way client and server communicate depends on used ØMQ protocol.

    15 

    16 We will take example on the medias conversion utility provided by 'pyams_media' package, which allows you

    17 to automatically convert medias files (videos...) asynchronously as soon as they are uploaded. The conversion

    18 process is a background process so doesn't return any result.

    19 

    20 The conversion process is a simple ØMQ process:

    21 

    22     >>> converter_address = '127.0.0.1:5555'

    23 

    24     >>> from pyams_zmq.process import ZMQProcess, process_exit_func

    25     >>>

    26     >>> class MediasConversionProcess(ZMQProcess):

    27     ...     """Medias conversion process"""

    28 

    29     >>> from multiprocessing import Process

    30     >>>

    31     >>> class ConversionProcess(Process):

    32     ...     """Conversion manager process"""

    33     ...

    34     ...     def __init__(self, settings, group=None, target=None, name=None, *args, **kwargs):

    35     ...         Process.__init__(self, group=group, target=target, name=name, args=args, kwargs=kwargs)

    36     ...         self.settings = settings

    37     ...

    38     ...     def run(self):

    39     ...         settings = self.settings

    40     ...         path  = settings['path']

    41     ...         format = settings['format']

    42     ...         # just image you're doing anything you want with these settings!

    43 

    44 To be sure to run asynchronously, this process is managed by a thread:

    45 

    46     >>> import time

    47     >>> from threading import Thread

    48     >>>

    49     >>> class ConversionThread(Thread):

    50     ...     """Conversion thread"""

    51     ...

    52     ...     def __init__(self, process):

    53     ...         Thread.__init__(self)

    54     ...         self.process = process

    55     ...

    56     ...     def run(self):

    57     ...         self.process.start()

    58     ...         self.process.join()

    59 

    60 The conversion handler is the simple class to which conversion is delegated:

    61 

    62     >>> class ConversionHandler(object):

    63     ...     """Conversion handler"""

    64     ...

    65     ...     def convert(self, data):

    66     ...         ConversionThread(ConversionProcess(data)).start()

    67     ...         return [200, 'OK']

    68 

    69 The message handler receives the message and handle it:

    70 

    71     >>> from pyams_zmq.handler import ZMQMessageHandler

    72     >>>

    73     >>> class ConversionMessageHandler(ZMQMessageHandler):

    74     ...

    75     ...     handler = ConversionHandler

    76 

    77 The ØMQ process is generally started on application startup:

    78 

    79     >>> import atexit

    80     >>>

    81     >>> process = MediasConversionProcess(converter_address, ConversionMessageHandler)

    82     >>> process.start()

    83     >>> time.sleep(2)

    84     >>> if process.is_alive():

    85     ...     atexit.register(process_exit_func, process=process)

    86     <function process_exit_func at 0x...>

    87 

    88 Once all these elements are in place, you just have to create a ØMQ client context, open a connection and send a

    89 message:

    90 

    91     >>> import zmq

    92     >>> settings = {'path': '/this/is/my/path',

    93     ...             'format': 'JPEG'}

    94     >>> message = ['convert', settings]

    95     >>> context = zmq.Context()

    96     >>> socket = context.socket(zmq.REQ)

    97     >>> socket.connect('tcp://' + converter_address)

    98     >>> socket.send_json(message)

    99     >>> socket.recv_json()

   100     [200, 'OK']