f818f1f02c
* This patch adds the base infrastructure for the new concept that we call Action Providers. It will allow to refactor Mistral in a way that all action management will be encapsulated with action providers. For example, Mistral Engine needs to schedule actions while processing a workflow. Now it has to access DB itself to find an action definition (meta info about what this action is, like python class, input params etc.), then prepare input parameters, validate parameters and send a message to an executor to run it. In many other places, Mistral also directly access DB to fetch an action definition. It's not flexible because we assume that definitions of Mistral actions must always be stored in DB. The concept of an Action Provider allows moving away from that limitation. A particular implementation of the ActionProvider interface can store action definitions in any suitable way, even fetching them using various transport protocols like AMQP, HTTP, TCP, or anything else. An action provider may also generate action definitions dynamically, like creating wrappers around a set of operating system commands. But for the rest of the system it won't matter what happens inside action providers. All details will be hidden behind a unified interface. * Added ActionDescriptor interface and its convenience base abstract implementation. ActionDescriptor is an entity representing an action before it's instantiated. It carries the most important meta information about an action like name, description, input parameters etc. It is also responsible for validating action input parameters and instantiating a real action. * Added PythonActionDescriptor which represents a regular action written as a Python class. * Added CompositeActionProvider that delegates calls find() and find_all() to a collection of other action providers. * Minor style changes. Partially implements: bp/mistral-action-providers Change-Id: Ic9108c9293731b3576081c75f2786e1156ba0ccd
82 lines
2.8 KiB
Python
82 lines
2.8 KiB
Python
# Copyright 2013 - Mirantis, Inc.
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# Copyright 2015 - StackStorm, Inc.
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# Copyright 2016 - Brocade Communications Systems, Inc.
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# Copyright 2016 - Red Hat, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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class MistralExceptionBase(Exception):
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"""Base class for Mistral specific errors and exceptions.
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A common parent class to derive MistralError and MistralException
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classes from.
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"""
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message = "An unknown error occurred"
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http_code = 500
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def __init__(self, message=None):
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if message is not None:
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self.message = message
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super(MistralExceptionBase, self).__init__(
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'%d: %s' % (self.http_code, self.message))
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@property
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def code(self):
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"""This is here for webob to read.
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https://github.com/Pylons/webob/blob/master/webob/exc.py
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"""
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return self.http_code
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def __str__(self):
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return self.message
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class MistralError(MistralExceptionBase):
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"""Mistral specific error.
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Reserved for situations that can't be automatically handled. When it occurs
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it signals that there is a major environmental problem like invalid startup
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configuration or implementation problem (e.g. some code doesn't take care
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of certain corner cases). From architectural perspective it's pointless to
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try to handle this type of problems except doing some finalization work
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like transaction rollback, deleting temporary files etc.
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"""
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message = "An unknown error occurred"
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class MistralException(Exception):
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"""Mistral specific exception.
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Reserved for situations that are not critical for program continuation.
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It is possible to recover from this type of problems automatically and
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continue program execution. Such problems may be related with invalid user
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input (such as invalid syntax) or temporary environmental problems.
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In case if an instance of a certain exception type bubbles up to API layer
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then this type of exception it must be associated with an http code so it's
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clear how to represent it for a client.
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To correctly use this class, inherit from it and define a 'message' and
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'http_code' properties.
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"""
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message = "An unknown exception occurred"
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class ActionException(MistralException):
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message = "Failed to process an action"
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