node-workflow

Task orchestration API and runners

npm install node-workflow
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Tasks Workflows Orchestration API and Runners.

Overview

Either if you are building a completely new system composed of many discreet API applications, each of them with a clearly defined area of responsibility, or in the case you are trying to assemble a collaboration channel between an heterogeneous set of totally unrelated API applications, you need a way to orchestrate interactions between these applications.

So a workflow is effectively an orchestration.

You want a workflow, because it gives you a way to decompose a complex series of operations down to a sequence of discreet tasks with a state machine.

The sequence of tasks is more complex than just a series. The tasks of course can fail, and so you need to deal with timeouts, retries, "stuck" flows, etc.

You can define a workflow and its tasks using an arbitrarily complex language. Or you can keep it simple by taking some assumptions:

  • Code is the definition language.
  • Tasks are independent. Can be used into different workflows.
  • The only way of communication between tasks is the workflow. Tasks can add, remove or modify properties of the workflow.
  • If a task requires a specific property of the workflow to be present, the task can fail, or re-schedule itself within the workflow, or ...

node-workflow

This package provides a way to define re-usable workflows using JSON and run concrete jobs with specific targets and parameters based on such workflows.

Workflow Runners

In order to execute the jobs, at least one WorkflowRunner must be up and ready to take jobs. An arbitrary number of runners can be used on any set of hosts; configuration must match.

An example WorkflowRunner is provided with the package and can be started with:

./bin/workflow-runner path/to/config.json

(The examples directory contains the file config.json.sample which can be used as reference).

You can create workflows and jobs either by using the provided REST API(s), or by embedding this module's API into your own system(s). The former will be easier to get up and running, but you should use the latter when:

  • You want to use the Worflow API in a (node.js) application that is not the bundled REST API.
  • You want to use a different backend storage system, or otherwise change the assumptions of the bundled REST API

The package also provides a binary file to run the WorkflowAPI using the same configuration file we pass to our WorkflowRunner:

./bin/workflow-api path/to/config.json

See demo section below for more details about both approaches.

Development

Pre-requirements:

  • Working Redis Server. (Version 2.4.+).

Clone the repo and build the deps:

git clone git://github.com/kusor/node-workflow.git
cd node-workflow
make all

Note make all will setup all the required dependencies, node modules and run make check and make test. In order to just setup node modules, make setup is enough.

To run the Workflow API server:

./bin/workflow-api path/to/config.json

To run a Job Runner:

./bin/workflow-runner path/to/config.json

Note that it's perfectly fine to run more than one Runner, either on the same or different machines, as far as they have access to Redis Server.

Testing

make test

Pre-commit git hook

In order to run make prepush before every commit, add the following to a file called .git/hooks/pre-commit and chmod +x it:

#!/bin/sh
# Run make prepush before allow commit

set -e

make prepush

exit 0

Obviously, if you've made a change not affecting source code files but, for example only docs, you can skip this hook by passing the option --no-verify to the git commit command.

Demo

The workflow-example repository contains everything needed to illustrate:

  • An example config file - config.json.sample which should be renamed to config.json and modified to properly match your local environment.

Remember that, in order to process any job the workflow-runner needs to be initialized pointing to the aforementioned configuration file:

./node_modules/.bin/workflow-runner config.json

Also, in order to be able to run the API based example mentioned below, the workflow-api HTTP server needs to be up and running too:

./node_modules/.bin/workflow-api config.json

Contents for the other files within the workflow-examples repository are:

  • An example of how to use node-workflow as a node module in order to create workflows, queue jobs and wait for the results. See module.js.
  • Also, an example of how to achieve same goal using Workflow API instead of the node module. See api.js.
  • Both examples share the same workflow definition, contained at the file shared-workflow.js. The beginning of the aforementioned files can be useful to understand the differences when trying to create a workflow using these different approaches.
  • Finally, this directory also contains a file node.js which does exactly the same thing than the workflow/job does - create and star a gist using your github's username and password - but straight from NodeJS. This file is useful in order to understand the differences between writing code to be executed by NodeJS directly, and using it to create workflows and the associated tasks. Remember code withing tasks runs sandboxed using Node's VM API and that tasks are totally independent, and run each one on its own child process.

Also, see example.js for more options when defining workflows and the different possibilities for tasks fallbacks, retries, timeouts ...

Repository

deps/           Git submodules and/or commited 3rd-party deps.
                See "node_modules/" for node.js deps.
docs/           Project docs (restdown)
lib/            Source files.
node_modules/   Node.js deps, either populated at build time or commited.
pkg/            Package lifecycle scripts
test/           Test suite (using node-tap)
tools/          Miscellaneous dev/upgrade/deployment tools and data.
Makefile
package.json    npm module info
README.md

TODO

See https://github.com/kusor/node-workflow/issues.

LICENSE

The MIT License (MIT) Copyright (c) 2012 Pedro Palazón Candel

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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