Metadata-Version: 2.1
Name: pymulproc
Version: 0.1.2
Summary: A tiny python library to handle multiprocessing communication
Home-page: https://github.com/d2gex/pymulproc
Author: Dan G
Author-email: daniel.garcia@d2garcia.com
License: UNKNOWN
Description: ==========================================================
        ``pymulproc`` a tiny multiprocessing communication library
        ==========================================================
        
        .. image:: https://travis-ci.com/d2gex/pymulproc.svg?branch=master
            :target: https://travis-ci.com/d2gex/pymulproc
        
        .. image:: https://img.shields.io/badge/pypi_package-0.1.2-brightgreen.svg
            :target: #
        
        .. image:: https://img.shields.io/badge/coverage-98%25-brightgreen.svg
            :target: #
        
        **pymulproc** is a tiny library to handle the communication between multiple processes without external
        dependencies other than Python's standard library. It is based purely in the multiprocessing library and provides a
        common interface for both PIPE and QUEUE communication.
        
        pymulproc Protocol
        ===================
        **pymulproc** uses a simple python list as the basis of the communication with the following fields:
        
        1. ``request``: a **required** string indicating the other peer what the operation is about.
        2. ``sender pid``: a **required** integer indicating the PID of the processing sending the datagram.
        3. ``recipient pid``: an **optional** integer indicating the PID of the process which this message is targeted to.
        4. ``data``: an **optional** python data structure containing the information intended for the other peer.
        
        In turns the requests sent in the data structure could be anything however **pymulproc** uses the following standards:
        
        6. ``REQ_DO``: requests that indicates the other peer to do a task.
        7. ``REQ_FINISHED``: requests that indicates the other peer that the task has been done.
        8. ``REQ_DIE``: requests that indicates the other peer to stop and die as soon as possible. Practically a poison pill.
        
        Example of valid message structures are shown below. **The message must always have a length of 4**:
        
        .. code-block:: python
        
            ['DO', 1234, 12345, {'value': 20}]  # request, sender PID, recipient PID, data
            ['DO', 1234, 12345, None]  # request, sender PID, recipient PID
            ['DIE', 1234, None, None]  # request, sender PID
        
        pymulproc API
        ===================
        **pymulproc** offers a common API interface for the conversation exchange between a parent process and its children
        for both PIPE and QUEUE communication as follows:
        
        9.  ``send``: sends a message down the PIPE for 1:1 conversation or put a message in a JoinedQueue for 1:M, M:1 and M:M
            conversations.
        10. ``receive``: check if there is a message in the PIPE or at the front of the QUEUE for the process making such
            an enquiry. if the message is not intended for the process making the enquiry False is returned. In case the
            communication is done via QUEUEs, the method puts back the message in the queue so that the targeted process can
            later on fetch it.
        
        Queue's communication add two more specific method: ``queue_empty`` to check if the queue is empty of tasks and
        ``queue_join`` to wait there until all the queue is empty.
        
        Among the optional parameters of the  ``send`` method signature shown below, is worthwhile highlighting ``sender_pid``.
        If provided, such integer is added to the message as sender PID. Otherwise the process will add its own
        PID.
        
        ``send`` will try to place the message in the queue, for queue communication only, a few times before raising an
        exception. The amount of tries can be configured when instantiating the connection handler - see ``QueueCommunicationApi``
        class' constructor for further details.
        
        .. code-block:: python
        
            @abc.abstractmethod
                def send(self, request, sender_pid=None, recipient_pid=None, data=None):
        
        ``receive`` is a High Order function and may take a ``func`` keyword argument associated to a function that applies
        an operation to the message at the front of the queue. If the result is True, then the message is for the enquiring
        process. Otherwise it is 'reinserted' at the back of the queue for other processes to check on it.
        
        If not parameters are passed, it is understood that the message at front of the queue is always for enquiring process.
        
        Additionally if ``block=True`` is passed to ``receive``, the process enquiring the queue will block while the queue
        remains empty. It will then "*wake up*" and check the queue again when another process sends information in via
        ``send``.
        
        An example where the criteria to check if the message is for the enquiring process always fails, is shown below:
        
        .. code-block:: python
        
            child.receive(lambda x: False)
        
        
        Installing pymulproc
        ====================
        
        **pymulproc** is available on PyPI_, so you can install it with ``pip``::
        
            $ pip install pymulproc
        
        
        pymulproc PIPE communication example
        ======================================
        Below a simple example of PIPE communication betwen a parent and a single child process is shown:
        
        .. code-block:: python
        
            import multiprocessing
            from pymulproc import factory, mpq_protocol
        
            def test_simple_pipe_communication():
        
                pipe_factory = factory.PipeCommunication()
                parent = pipe_factory.parent()
                child = pipe_factory.child()
        
                def call_child(_child):
                    _child.send(mpq_protocol.REQ_TEST_CHILD)
        
                child_process = multiprocessing.Process(name='child_process_',
                                                        target=call_child,
                                                        args=(child, ))
                child_process.start()
                child_process.join()
                message = parent.receive()
                request_offset = mpq_protocol.S_PID_OFFSET - 1
                assert message[request_offset] == mpq_protocol.REQ_TEST_CHILD
        
        pymulproc simple 1:N QUEUE communication example
        =================================================
        The example below shows how child processes send some data back to the parent. Notice how the parent passes no ``func``
        parameter to ``receive`` as all messages placed in the queue by the child processes are intended for the parent itself:
        
        .. code-block:: python
        
            import multiprocessing
            from pymulproc import factory, mpq_protocol
        
        
            class ChildProcess:
                def __init__(self, identifier, parent_pid, conn):
                    self.id = identifier
                    self.conn = conn
                    self.parent_pid = parent_pid
                    self.pid = multiprocessing.current_process().pid
        
                def is_message_for_me(self, message):
                    '''The message is for me if either the recipient_pid coincides with my pid or is None - None indicates
                    that the message is for everyone
                    '''
                    return message[mpq_protocol.S_PID_OFFSET + 1] == self.pid or not message[mpq_protocol.S_PID_OFFSET + 1]
        
                def run(self, **kwargs):
                    '''Sends the data passed as keyword parameter to the parent process:
                    '''
        
                    data = kwargs.get('data', None)
                    self.conn.send(mpq_protocol.REQ_FINISHED, data=data)
        
        
            def call_child(identifier, parent_pid, q_factory, data):
                child = ChildProcess(identifier, parent_pid, q_factory.child())
                child.run(data=data)
        
        
            def test_children_to_parent_communication():
                '''Simple test where all child processes send a message to the parent process
        
                All children are initiated with a value that is sent to the parent for it to process it.
                '''
        
                queue_factory = factory.QueueCommunication()
                parent = queue_factory.parent()
                parent_pid = multiprocessing.current_process().pid
        
                # Prepare list of processes to start and pass the value = 3 to each child process
                child_processes = []
                val = 3
                for offset in range(5):
                    child_process = multiprocessing.Process(name=f'child_process_{offset}',
                                                            target=call_child,
                                                            args=(offset + 1, parent_pid, queue_factory, val))
                    child_processes.append(child_process)
        
                # Start processes
                for child in child_processes:
                    child.start()
        
                # Wait for the processes to finish
                for child in child_processes:
                    child.join()
        
                # Receive the data from all children
                counter = 0
                data_offset = mpq_protocol.S_PID_OFFSET + 2
                while not parent.queue_empty():
                    message = parent.receive()
                    counter += message[data_offset]
        
                # Ensure the queue is empty - no loose strings
                parent.queue_join()
        
                # Ensure we got the right data from children
                assert counter == val * len(child_processes)
        
        
        More examples
        =============
        
        For a more complex example look at the test test_parent_full_duplex_communication_with_children_stress_test_ where
        a full duplex communication between the parent and child processes occurs. Also a poison pill is sent to all children
        when they are no longer needed.
        
        .. _test_parent_full_duplex_communication_with_children_stress_test: https://github.com/d2gex/pymulproc/blob/master/tests/test_queue_communication.py
        .. _PyPI: http://pypi.python.org/pypi/bleach
        
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Environment :: Console
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Requires-Python: >=3.6
Description-Content-Type: text/x-rst
