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# Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import contextlib
import logging
import os
import sys
logging.basicConfig(level=logging.ERROR)
self_dir = os.path.abspath(os.path.dirname(__file__))
top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
os.pardir,
os.pardir))
sys.path.insert(0, top_dir)
sys.path.insert(0, self_dir)
from oslo_utils import uuidutils
import taskflow.engines
from taskflow.patterns import linear_flow as lf
from taskflow.persistence import models
from taskflow import task
import example_utils as eu # noqa
# INTRO: In this example linear_flow is used to group three tasks, one which
# will suspend the future work the engine may do. This suspend engine is then
# discarded and the workflow is reloaded from the persisted data and then the
# workflow is resumed from where it was suspended. This allows you to see how
# to start an engine, have a task stop the engine from doing future work (if
# a multi-threaded engine is being used, then the currently active work is not
# preempted) and then resume the work later.
#
# Usage:
#
# With a filesystem directory as backend
#
# python taskflow/examples/resume_from_backend.py
#
# With ZooKeeper as backend
#
# python taskflow/examples/resume_from_backend.py \
# zookeeper://127.0.0.1:2181/taskflow/resume_from_backend/
# UTILITY FUNCTIONS #########################################
def print_task_states(flowdetail, msg):
eu.print_wrapped(msg)
print("Flow '{}' state: {}".format(flowdetail.name, flowdetail.state))
# Sort by these so that our test validation doesn't get confused by the
# order in which the items in the flow detail can be in.
items = sorted((td.name, td.version, td.state, td.results)
for td in flowdetail)
for item in items:
print(" %s==%s: %s, result=%s" % item)
def find_flow_detail(backend, lb_id, fd_id):
conn = backend.get_connection()
lb = conn.get_logbook(lb_id)
return lb.find(fd_id)
# CREATE FLOW ###############################################
class InterruptTask(task.Task):
def execute(self):
# DO NOT TRY THIS AT HOME
engine.suspend()
class TestTask(task.Task):
def execute(self):
print('executing %s' % self)
return 'ok'
def flow_factory():
return lf.Flow('resume from backend example').add(
TestTask(name='first'),
InterruptTask(name='boom'),
TestTask(name='second'))
# INITIALIZE PERSISTENCE ####################################
with eu.get_backend() as backend:
# Create a place where the persistence information will be stored.
book = models.LogBook("example")
flow_detail = models.FlowDetail("resume from backend example",
uuid=uuidutils.generate_uuid())
book.add(flow_detail)
with contextlib.closing(backend.get_connection()) as conn:
conn.save_logbook(book)
# CREATE AND RUN THE FLOW: FIRST ATTEMPT ####################
flow = flow_factory()
engine = taskflow.engines.load(flow, flow_detail=flow_detail,
book=book, backend=backend)
print_task_states(flow_detail, "At the beginning, there is no state")
eu.print_wrapped("Running")
engine.run()
print_task_states(flow_detail, "After running")
# RE-CREATE, RESUME, RUN ####################################
eu.print_wrapped("Resuming and running again")
# NOTE(harlowja): reload the flow detail from backend, this will allow us
# to resume the flow from its suspended state, but first we need to search
# for the right flow details in the correct logbook where things are
# stored.
#
# We could avoid re-loading the engine and just do engine.run() again, but
# this example shows how another process may unsuspend a given flow and
# start it again for situations where this is useful to-do (say the process
# running the above flow crashes).
flow2 = flow_factory()
flow_detail_2 = find_flow_detail(backend, book.uuid, flow_detail.uuid)
engine2 = taskflow.engines.load(flow2,
flow_detail=flow_detail_2,
backend=backend, book=book)
engine2.run()
print_task_states(flow_detail_2, "At the end")
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