Kuadrant/policy-machinery

Policy Machinery is a Go library that provides machinery for implementing Gateway API policies and policy controllers.

The tool solves the problem of building custom controllers that need to manage policies attached to Gateway API resources. It works by providing types for modeling topologies of targetable network resources and their attached policies, along with helpers for constructing and testing these topologies. The library offers two reconciliation patterns: state-of-the-world, which coalesces events into a single reconciliation call, and incremental events for more granular per-event reconciliation. It includes support for reconciliation workflows to handle dependencies and concurrent tasks, as well as subscriptions for matching on specific event types. Developers can define custom policy types with their own merge strategies, including examples using JSON patch and Kuadrant Defaults & Overrides patterns.

The tool is suited for teams building custom Kubernetes controllers that work with Gateway API resources and need to attach and manage policies across a topology of gateways, routes, and services. It provides a specialized package for implementing Gateway API-specific controllers that automatically infer links between network objects like GatewayClasses, Gateways, and HTTPRoutes. The library includes topology expansion options to automatically add inner sections of resources as targetables, with links adjusted accordingly. A full example controller is provided that demonstrates watching Gateway API resources alongside four kinds of policies.

The project shows active development with regular commits addressing controller functionality and topology handling. The codebase demonstrates attention to test coverage and documentation through its inclusion of comprehensive examples. Development activity reflects ongoing refinement of the controller abstraction and reconciliation patterns, with updates to how watchers and predicates are implemented.