IPython/kernel/taskclient.py

# encoding: utf-8
# -*- test-case-name: IPython.kernel.tests.test_taskcontrollerxmlrpc -*-

"""
A blocking version of the task client.
"""

__docformat__ = "restructuredtext en"

#-------------------------------------------------------------------------------
#  Copyright (C) 2008  The IPython Development Team
#
#  Distributed under the terms of the BSD License.  The full license is in
#  the file COPYING, distributed as part of this software.
#-------------------------------------------------------------------------------

#-------------------------------------------------------------------------------
# Imports
#-------------------------------------------------------------------------------

from zope.interface import Interface, implements
from twisted.python import components

try:
    from foolscap.api import DeadReferenceError
except ImportError:
    from foolscap import DeadReferenceError

from IPython.kernel.twistedutil import blockingCallFromThread
from IPython.kernel import task, error
from IPython.kernel.mapper import (
    SynchronousTaskMapper,
    ITaskMapperFactory,
    IMapper
)
from IPython.kernel.parallelfunction import (
    ParallelFunction, 
    ITaskParallelDecorator
)

#-------------------------------------------------------------------------------
# The task client
#-------------------------------------------------------------------------------

class IBlockingTaskClient(Interface):
    """
    A vague interface of the blocking task client
    """
    pass

class BlockingTaskClient(object):
    """
    A blocking task client that adapts a non-blocking one.
    """
    
    implements(
        IBlockingTaskClient,
        ITaskMapperFactory,
        IMapper,
        ITaskParallelDecorator
    )
    
    def __init__(self, task_controller):
        self.task_controller = task_controller
        self.block = True

    def _bcft(self, *args, **kwargs):
        try:
            result = blockingCallFromThread(*args, **kwargs)
        except DeadReferenceError:
            raise error.ConnectionError(
                """A connection error has occurred in trying to connect to the
                controller. This is usually caused by the controller dying or 
                being restarted. To resolve this issue try recreating the 
                task client."""
            )
        else:
            return result

    def run(self, task, block=False):
        """Run a task on the `TaskController`.
        
        See the documentation of the `MapTask` and `StringTask` classes for
        details on how to build a task of different types.
        
        :Parameters:
            task : an `ITask` implementer
        
        :Returns: The int taskid of the submitted task.  Pass this to 
            `get_task_result` to get the `TaskResult` object.
        """
        tid = self._bcft(self.task_controller.run, task)
        if block:
            return self.get_task_result(tid, block=True)
        else:
            return tid
    
    def get_task_result(self, taskid, block=False):
        """
        Get a task result by taskid.
        
        :Parameters:
            taskid : int
                The taskid of the task to be retrieved.
            block : boolean
                Should I block until the task is done?
        
        :Returns: A `TaskResult` object that encapsulates the task result.
        """
        return self._bcft(self.task_controller.get_task_result,
            taskid, block)
    
    def abort(self, taskid):
        """
        Abort a task by taskid.
        
        :Parameters:
            taskid : int
                The taskid of the task to be aborted.
        """
        return self._bcft(self.task_controller.abort, taskid)
    
    def barrier(self, taskids):
        """Block until a set of tasks are completed.
        
        :Parameters:
            taskids : list, tuple
                A sequence of taskids to block on.
        """
        return self._bcft(self.task_controller.barrier, taskids)
    
    def spin(self):
        """
        Touch the scheduler, to resume scheduling without submitting a task.
        
        This method only needs to be called in unusual situations where the
        scheduler is idle for some reason. 
        """
        return self._bcft(self.task_controller.spin)
    
    def queue_status(self, verbose=False):
        """
        Get a dictionary with the current state of the task queue.
        
        :Parameters:
            verbose : boolean
                If True, return a list of taskids.  If False, simply give
                the number of tasks with each status.
        
        :Returns:
            A dict with the queue status.
        """
        return self._bcft(self.task_controller.queue_status, verbose)
    
    def clear(self):
        """
        Clear all previously run tasks from the task controller.
        
        This is needed because the task controller keep all task results
        in memory.  This can be a problem is there are many completed
        tasks.  Users should call this periodically to clean out these
        cached task results.
        """
        return self._bcft(self.task_controller.clear)
    
    def map(self, func, *sequences):
        """
        Apply func to *sequences elementwise.  Like Python's builtin map.
        
        This version is load balanced.
        """
        return self.mapper().map(func, *sequences)

    def mapper(self, clear_before=False, clear_after=False, retries=0, 
                recovery_task=None, depend=None, block=True):
        """
        Create an `IMapper` implementer with a given set of arguments.
        
        The `IMapper` created using a task controller is load balanced.
        
        See the documentation for `IPython.kernel.task.BaseTask` for 
        documentation on the arguments to this method.
        """
        return SynchronousTaskMapper(self, clear_before=clear_before, 
            clear_after=clear_after, retries=retries, 
            recovery_task=recovery_task, depend=depend, block=block)
    
    def parallel(self, clear_before=False, clear_after=False, retries=0, 
        recovery_task=None, depend=None, block=True):
        mapper = self.mapper(clear_before, clear_after, retries,
            recovery_task, depend, block)
        pf = ParallelFunction(mapper)
        return pf

components.registerAdapter(BlockingTaskClient,
            task.ITaskController, IBlockingTaskClient)