187 lines
6.7 KiB
Python
187 lines
6.7 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import json
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import logging
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import os
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import sys
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import time
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logging.basicConfig(level=logging.ERROR)
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top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
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os.pardir,
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os.pardir))
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sys.path.insert(0, top_dir)
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from oslo_utils import uuidutils
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from taskflow import engines
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from taskflow.listeners import printing
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from taskflow.patterns import graph_flow as gf
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from taskflow.patterns import linear_flow as lf
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from taskflow import task
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from taskflow.utils import misc
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# INTRO: This example walks through a miniature workflow which simulates
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# the reception of an API request, creation of a database entry, driver
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# activation (which invokes a 'fake' webservice) and final completion.
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#
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# This example also shows how a function/object (in this class the url sending)
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# that occurs during driver activation can update the progress of a task
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# without being aware of the internals of how to do this by associating a
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# callback that the url sending can update as the sending progresses from 0.0%
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# complete to 100% complete.
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class DB(object):
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def query(self, sql):
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print("Querying with: %s" % (sql))
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class UrlCaller(object):
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def __init__(self):
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self._send_time = 0.5
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self._chunks = 25
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def send(self, url, data, status_cb=None):
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sleep_time = float(self._send_time) / self._chunks
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for i in range(0, len(data)):
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time.sleep(sleep_time)
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# As we send the data, each chunk we 'fake' send will progress
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# the sending progress that much further to 100%.
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if status_cb:
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status_cb(float(i) / len(data))
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# Since engines save the output of tasks to a optional persistent storage
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# backend resources have to be dealt with in a slightly different manner since
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# resources are transient and can *not* be persisted (or serialized). For tasks
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# that require access to a set of resources it is a common pattern to provide
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# a object (in this case this object) on construction of those tasks via the
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# task constructor.
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class ResourceFetcher(object):
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def __init__(self):
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self._db_handle = None
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self._url_handle = None
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@property
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def db_handle(self):
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if self._db_handle is None:
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self._db_handle = DB()
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return self._db_handle
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@property
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def url_handle(self):
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if self._url_handle is None:
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self._url_handle = UrlCaller()
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return self._url_handle
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class ExtractInputRequest(task.Task):
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def __init__(self, resources):
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super(ExtractInputRequest, self).__init__(provides="parsed_request")
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self._resources = resources
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def execute(self, request):
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return {
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'user': request.user,
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'user_id': misc.as_int(request.id),
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'request_id': uuidutils.generate_uuid(),
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}
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class MakeDBEntry(task.Task):
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def __init__(self, resources):
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super(MakeDBEntry, self).__init__()
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self._resources = resources
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def execute(self, parsed_request):
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db_handle = self._resources.db_handle
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db_handle.query("INSERT %s INTO mydb" % (parsed_request))
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def revert(self, result, parsed_request):
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db_handle = self._resources.db_handle
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db_handle.query("DELETE %s FROM mydb IF EXISTS" % (parsed_request))
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class ActivateDriver(task.Task):
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def __init__(self, resources):
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super(ActivateDriver, self).__init__(provides='sent_to')
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self._resources = resources
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self._url = "http://blahblah.com"
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def execute(self, parsed_request):
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print("Sending billing data to %s" % (self._url))
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url_sender = self._resources.url_handle
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# Note that here we attach our update_progress function (which is a
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# function that the engine also 'binds' to) to the progress function
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# that the url sending helper class uses. This allows the task progress
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# to be tied to the url sending progress, which is very useful for
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# downstream systems to be aware of what a task is doing at any time.
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url_sender.send(self._url, json.dumps(parsed_request),
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status_cb=self.update_progress)
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return self._url
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def update_progress(self, progress, **kwargs):
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# Override the parent method to also print out the status.
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super(ActivateDriver, self).update_progress(progress, **kwargs)
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print("%s is %0.2f%% done" % (self.name, progress * 100))
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class DeclareSuccess(task.Task):
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def execute(self, sent_to):
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print("Done!")
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print("All data processed and sent to %s" % (sent_to))
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class DummyUser(object):
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def __init__(self, user, id_):
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self.user = user
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self.id = id_
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# Resources (db handles and similar) of course can *not* be persisted so we
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# need to make sure that we pass this resource fetcher to the tasks constructor
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# so that the tasks have access to any needed resources (the resources are
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# lazily loaded so that they are only created when they are used).
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resources = ResourceFetcher()
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flow = lf.Flow("initialize-me")
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# 1. First we extract the api request into a usable format.
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# 2. Then we go ahead and make a database entry for our request.
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flow.add(ExtractInputRequest(resources), MakeDBEntry(resources))
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# 3. Then we activate our payment method and finally declare success.
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sub_flow = gf.Flow("after-initialize")
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sub_flow.add(ActivateDriver(resources), DeclareSuccess())
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flow.add(sub_flow)
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# Initially populate the storage with the following request object,
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# prepopulating this allows the tasks that dependent on the 'request' variable
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# to start processing (in this case this is the ExtractInputRequest task).
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store = {
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'request': DummyUser(user="bob", id_="1.35"),
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}
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eng = engines.load(flow, engine='serial', store=store)
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# This context manager automatically adds (and automatically removes) a
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# helpful set of state transition notification printing helper utilities
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# that show you exactly what transitions the engine is going through
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# while running the various billing related tasks.
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with printing.PrintingListener(eng):
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eng.run()
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