47 lines
2 KiB
Markdown
47 lines
2 KiB
Markdown
# An Asynchronous, Distributed Task Engine
|
|
|
|
This document presents a design without reference implementation for a distributed programming system;
|
|
sometimes called a workflow engine.
|
|
It is intended to provide architectural level clarity allowing for the development of alternative designs or implementations as may suit.
|
|
|
|
## Problem Statement
|
|
|
|
In building, operating and maintaining distributed systems (many computers in concert) engineers face a tooling gap.
|
|
|
|
Within the confines of a single computer, we have shells (`bash`, `csh`, `zsh`, `oil` etc.)
|
|
and a suite of small programs which mesh together well enough for the completion of small tasks with ad-hoc automation.
|
|
This is an enormous tooling win, as it allows small tasks to be automated at least for a time with a minimum of effort and with tools close to hand.
|
|
|
|
In interacting with networks, communicating between computers is difficult with traditional tools and communication failure becomes an ever-present concern.
|
|
Traditional automation tools such as shells are inadequate for this environment because achieving network communication is excessively difficult.
|
|
|
|
In a distributed environment it cannot be assumed that a single machine can remain available to execute automation;
|
|
This requires an approach to automation which allows for the incremental execution of single tasks at a time with provisions for relocation and recovery should failure occur.
|
|
|
|
It also cannot be assumed that a single machine is sufficiently available to receive and process incoming events such as callbacks.
|
|
A distributed system is needed to wrangle distributed systems.
|
|
|
|
## Design Considerations
|
|
|
|
- Timeouts are everywhere
|
|
- Sub-Turing/boundable
|
|
-
|
|
|
|
## Architectural Overview
|
|
|
|
### Events
|
|
Things that will happen, or time out.
|
|
|
|
### Actions
|
|
Things the workflow will do, or time out.
|
|
|
|
### Bindings
|
|
Data the workflow either was given or computed.
|
|
|
|
### Conditionals
|
|
Decisions the workflow may make.
|
|
|
|
### Functions
|
|
A convenient way to talk about fragments of control flow graph.
|
|
|
|
### Tracing & Reporting
|