spiff-arena/SpiffWorkflow/specs/Execute.py

# -*- coding: utf-8 -*-

# Copyright (C) 2007 Samuel Abels
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
import subprocess

from ..task import TaskState
from .base import TaskSpec


class Execute(TaskSpec):

    """
    This class executes an external process, goes into WAITING until the
    process is complete, and returns the results of the execution.

    Usage:

    task = Execute(spec, 'Ping', args=["ping", "-t", "1", "127.0.0.1"])
        ... when workflow complete
    print workflow.get_task('Ping').results
    """

    def __init__(self, wf_spec, name, args=None, **kwargs):
        """
        Constructor.

        :type  wf_spec: WorkflowSpec
        :param wf_spec: A reference to the workflow specification.
        :type  name: str
        :param name: The name of the task spec.
        :type  args: list
        :param args: args to pass to process (first arg is the command).
        :type  kwargs: dict
        :param kwargs: kwargs to pass-through to TaskSpec initializer.
        """
        assert wf_spec is not None
        assert name is not None
        TaskSpec.__init__(self, wf_spec, name, **kwargs)
        self.args = args

    def _start(self, my_task, force=False):
        """Returns False when successfully fired, True otherwise"""
        if (not hasattr(my_task, 'subprocess')) or my_task.subprocess is None:
            my_task.subprocess = subprocess.Popen(self.args,
                                                  stderr=subprocess.STDOUT,
                                                  stdout=subprocess.PIPE)

        if my_task.subprocess:
            my_task.subprocess.poll()
            if my_task.subprocess.returncode is None:
                # Still waiting
                return False
            else:
                results = my_task.subprocess.communicate()
                my_task.results = results
                return True
        return False

    def _update_hook(self, my_task):
        if not self._start(my_task):
            my_task._set_state(TaskState.WAITING)
        else:
            return super(Execute, self)._update_hook(my_task)

    def serialize(self, serializer):
        return serializer.serialize_execute(self)

    @classmethod
    def deserialize(self, serializer, wf_spec, s_state):
        spec = serializer.deserialize_execute(wf_spec, s_state)
        return spec