Fleet Service

Library and command line tool to enable service based zero-downtime deployment strategies for CoreOS fleet.

Design choices

• Only instance based deployments are supported, non-instanced units will be removed
• Only indexed instances are supported, all other instances will be removed
• Expects the unit to do it's own health-checking/only exit with return 0/running when the application is actually running
• Will timeout if a unit doesn't reach it's desired state within the timeout limit. Overriding the default timeout is possible

Limitations

• Only does initial creates and updates using the fs create command, no other commands implemented yet
• Only 1 update strategy supported: stop 1st instance, start 1st instance, stop 2nd instance, start 2nd instance, etc
• Only Python 2.7 is supported because of http://click.pocoo.org/5/python3 and coreos/bugs#112
• Defaults are declared in both fs as well the fleet_helper module because of pallets/click#627
• Tries to adhere to the rule that instances and templates are homogenous, but it's not 100% compliant to it yet

How to use

# Download the binary and run it :)
fs --help

How to develop

# Create a virtualenv with python 2.7
virtualenv -p python2.7 .venv
# Activate the virtualenv
source .venv/bin/activate
# Install the dependencies
pip install -r requirements.txt -r requirements-build.txt
# Install fleet-service so you can work on it
pip install -e .

Building the single binary

# Make sure the frozen dependency versions are installed
pip install -r requirements-frozen.txt
# native build
pyinstaller --onefile fs.spec
# containerized Linux build
docker-compose -f docker-compose.build.yml run --rm builder

The fs binary can be found under the dist directory

References

• https://coreos.com/fleet/docs/latest/api-v1.html
• https://github.com/coreos/fleet/blob/master/Documentation/states.md