workflow-engine 0.1.0

a engine to process workflows and tasks

Workflow Engine

introduction

This module is used to implement workflows. Every workflow executes a list of tasks.

Installation

python -m pip install workflow_engine

Implementation

Processor

A Workflow processor is the main instance which will handle a list of entities and passes them to the assigned tasks. The handled entities should inherit from the workflow model type.

Since the workflow processor is an abstract class, the following methods have to be implemented in the inherited class:

• get_default_entries returns a list of unparsed entries
• get_entry parses the raw entries retrieved by the previous method to an object which inherits from the WorkflowModel
• filter define some preconditions
• get_tasks returns a list of instances which inherit from the workflow task
• write_entry handle a processed (successfully or unsuccessfully) entry. Write it to the cache or to the disk
• close handle the finale state of the workflow

Model

Basic implementation of an entity. Delivers field and methods to check, wether the task has already been executed, if there is a related error or if the entry should be executed again.

Task

Basic implementation of a task which should be executed for a workflow

Status

The following use cases can be handled:

flow type	Exception	StatusException	OnSuccess
skip	-	-	x
interrupt	x	x	-
repeat	(-)	x	x

• Exception in case of an Exception which is not an instance of
  StatusException the workflow will be interrupted. An operator has the possibility to set the repeat property
• StatusException will interrupt the workflow and set the Status object which can contain any repeat property
• OnSuccess can return a Status can contain any repeat property. To skip the task it is not necessary to implement a dedicated status. Just return a Status to exit the task

Exception Handling

In case of unexpected Exceptions the workflow for the handled entry will be cancelled. The stacktrace will be logged. An unique id is assigned to each
exception. The error id will be persisted into your status file and into the logs.