float

float is a minimalistic configuration management toolkit to manage container-based services on bare-metal hardware or virtual machines (a.k.a. container orchestration framework). It is implemented as a series of Ansible plugins and roles that you should use from your own Ansible configuration.

Its main purpose is to provide a simple container-oriented environment, with minimal but complete features, to prepare services (and developers) for a full migration to something more sophisticated like Kubernetes.

Features

Some of these, especially when comparing against full-featured solutions like Kubernetes, are non-features:

• static service allocation - the service scheduler does not move containers at runtime in response to host failures, all changes happen at "configuration time" when running Ansible.
• 1:1 instance/host mapping - the scheduler won't run more than one instance of a service on each host.
• manual port assignments - you must manually pick a unique port for your services, there's no automatic allocation.
• service discovery protocol - DNS based.
• PKI management - all service-to-service communication can be encrypted and authenticated using a private PKI.
• builtin services - the toolkit provides a number of built-in services, such as monitoring, alerting, log collection and analysis, thorough audit functionality, private networking. These services are automatically configured and managed (though they can be extended).

Some of these "features" were selected in order to massively simplify the implementation (the scheduler and the service discovery layer are just a few hundred lines of Python all together), while trying to minimize cognitive and operational load. We may have failed on both those accounts.

Target

It should be clear from the list of "features" above, but this system isn't meant to provide high availability without some smartness in the services themselves. Its major limitation is the requirement for manual operator action in face of high-level environmental changes (loss of machines, changes in load/demand), so for instance it won't do much for a singly-homed service on a host that is dead. The system doesn't perform reactive actions at runtime (it is, in fact, implemented on top of a configuration management system).

However, it is possible to build reliable services on this infrastructure with cooperation from the service itself, by making the service use the available infrastructure primitives. Just with service discovery, and a relatively robust traffic routing layer, it's relatively straightforward to build partitioned or replicated services, where one can arbitrarily tune the threshold for manual operator intervention.

Documentation

More detailed documentation is available in the docs/ subdirectory, and in README files for individual Ansible roles:

General Documentation

• Quick start guide
• Reference (PDF)
• Notes on testing

Requirements

On the local machine (the one that will run Ansible), you're going to need Ansible, obviously, and a few small other custom tools used to manage credentials. These tools should be built on the local machine using Go:

sudo apt-get install golang
go install git.autistici.org/ale/x509ca@latest
go install git.autistici.org/ale/ed25519gen@latest
export PATH=$PATH:$HOME/go/bin

Altough not strictly a requirement, you will probably want to use a number of external services that are not provided by float itself:

• git repository hosting
• CI system to build container images
• a Docker registry