caravan 0.2.2

Light python framework for AWS SWF

Light python framework for AWS SWF

About this Project

Caravan is being used at Ludia for projects like marketing campaign system and on-demand distributed processing systems (thanks to hundreds of Lambda functions).

Feedbacks, ideas and contributions are highly welcomed. (Just open a Github issue).

• Code on Github

• PyPi

• Tests

• Doc: TODO

Focus of this project

Similar projects exists (like Simpleflow which seems mature). Here is where Caravan differs from existing projects:

• Support of AWS Lambda tasks

• Boto3

• KISS

• Bring your own workflow framework (standard implementations as contribs)

• No coupling between Decider code and Activity code

• Paster compatible config file

Features

• Decider worker

• Activity task worker TODO

• Commands to start/signal/terminate an arbitrary workflow execution

• Command to list open workflow execution

• Command to register a domain / list domains

Configuration

Caravan uses Boto3 to connect to AWS. See Boto 3 configuration guide for the complete documentation.

Warning

On AWS EC2, the metadata provider only provides the credentials, the must be provided by configuration.

Environment Variables

AWS_ACCESS_KEY_ID

The access key for your AWS account.

AWS_SECRET_ACCESS_KEY

The secret key for your AWS account.

AWS_DEFAULT_REGION

The default region to use, e.g. us-east-1.

AWS_PROFILE

The default credential and configuration profile to use, if any.

Configuration Files

The credentials file is located at ~/.aws/credentials:

[default]
# The access key for your AWS account
aws_access_key_id=<YOUR ACCESS KEY ID>

# The secret key for your AWS account
aws_secret_access_key=<YOUR SECRET KEY>

The settings file is located at ~/.aws/config:

[default]
# The default region when making requests
region=<REGION NAME>

It also supports profiles:

[profile dev-profile]
# The default region when using the dev-profile account
region=<REGION NAME>

Demo

Setup a SWF domain to run this example:

$ caravan-domain-register -n CaravanDemo --retention-days 1

Write a workflow type (see full demo)

from caravan import Workflow


class Demo(Workflow):

    """Noop workflow using the bare caravan API."""

    name = 'Demo'
    version = '0.1'
    default_execution_start_to_close_timeout = '600'
    default_task_start_to_close_timeout = '10'

    def run(self):
        self.task.print_events()
        self.task.add_decision('CompleteWorkflowExecution')

Run the decider with the Demo workflow:

$ caravan-decider -d CaravanDemo -m caravan.examples.demo -t default --verbose

Start an execution of the Demo workflow:

$ caravan-start -d CaravanDemo -n Demo -v 0.1 -i 1

(The Demo workflow will wait for 5 minutes)

List the executions:

$ caravan-list -d CaravanDemo
$ caravan-list -d CaravanDemo --oldest 2015-01-01

Send a signal to an execution:

$ caravan-signal -d CaravanDemo -i 1 -s PRINT --input 'Hello World!'
$ caravan-signal -d CaravanDemo -i 1 -s PRINT --input 'Lorem ipsum'
$ caravan-signal -d CaravanDemo -i 1 -s STOP

Terminate an execution:

$ caravan-terminate -d CaravanDemo -i 1

Similar projects

Python:

• Simpleflow: https://github.com/botify-labs/simpleflow

• Flowy: https://github.com/severb/flowy

• Garcon: https://github.com/xethorn/garcon

Ruby:

• AWS Flow: https://github.com/aws/aws-flow-ruby

References

• AWS Developer Guide for SWF

• AWS API reference for SWF

Development

Possibly use virtualenvwrapper to manage your virtualenvs.

$ mkvirtualenv caravan

or

$ virtualenv caravan

Clone and install development dependencies:

(caravan)$ git clone [e-mail]:pior/caravan.git
(caravan)$ cd caravan
(caravan)$ pip install -e .[dev]

Run tests:

(caravan)$ nosetests

Release

The release process use zest.releaser:

$ fullrelease

License

MIT licensed. See the bundled LICENSE file for more details