Hello everyone,
read on for my first draft of a requirements document for a Workflow CouchDB
Tiein.
greetings,
Benjamin
Zeta Components - Workflow CouchDB Tiein Design
~~~
:Author: Benjamin Eberlei
Introduction
Description
---
The WorkflowCouchDBTiein provides functionalities to load and save workflows
into CouchDB
and to start, save and resume executions by persisting the state into CouchDB.
Benefits of a CouchDB backend over the DatabaseTiein is the non-relational
structure of a workflow.
Each node and execution has different variables, state and dependencies.
Additionally a relational
implementation requires to split the workflow in many different tables,
reducing performance during
save and query operations. CouchDB could save workflow and executions in their
own documents
respectively, requiring only between one and three HTTP calls to CouchDB to
fetch and save all the workflow
related data again.
Additionally having the workflows (+history) and executions in single documents
makes the whole
workflow process much more readable and debugable for developers.
Current implementation
--
I have a current implementation to figure out some of the problems that might
come
with using CouchDB for workflow and it helped find some problems in Workflow
Base
component that have to be fixed before. However the code is not tested so I will
probably begin from scratch.
Requirements
The implementation should obviously work exactly like the base or database
workflows,
so that there are no differences using either one.
Design goals
- A thin HTTP Layer is provided with this component to speak to CouchDB
so that no third dependency needs to be introduced.
- Workflows, their Nodes and Executions will be assigned CouchDB UUIDs.
- Workflows and executions are saved into a single document each.
- Time inconsistencies due to changing workflows will be circumvented
by saving all versions of the workflow into a substructure and associating
each active execution with a workflow id and version.
- Document JSON structures are crafted in a way that developers can implement
their own queries on various variables of the execution state are possible
using CouchDB views.
