Module ctx 

The boundary between the controller and its environment.

ClusterControllerCtx is the single, strategy-agnostic boundary through which the controller pulls the signals a tick examines and applies the catalog mutations it derives. It carries primitive signals in and primitive catalog mutations out; it has no per-strategy state or vocabulary. The controller crate knows nothing about the Coordinator. The Coordinator implements this trait, which is what makes the controller testable against a fake implementation and extractable later without touching controller code.

The interface is pull-based: a tick fetches only the signals it actually examines (no eager all-clusters-all-replicas snapshot is pushed in), and the controller drives what is fetched. Read methods are batched so a separate-task deployment can bound its round-trips to the Coordinator.

Structs

AvailabilityZones

The availability zones a managed cluster’s replicas are provisioned across, in configured provisioning order.

BurstRecord

An active hydration-burst record, mirrored from durable state.

ClusterState

The durable state of a single managed cluster plus its observed replicas, as pulled through the ctx for one reconcile tick.

ExpectedClusterState

Compare-and-append witness over a managed cluster’s durable config: the fields a conditional write is conditioned on. The applier applies the write only if the cluster’s current config still projects to an equal witness.

ObservedReplica

A replica that actually exists on a cluster, as observed through the ctx.

ReconfigurationRecord

An in-flight graceful reconfiguration record, mirrored from durable state.

ReconfigurationTarget

The full config shape a reconfiguration is moving the cluster to. Distinct from a replica shape because it additionally carries replication_factor, a cluster-level rather than replica-level dimension.

ReplicaShape

The config dimensions that distinguish one replica from another. Two replicas with equal shape are interchangeable. An AVAILABILITY ZONES difference is a shape difference, but only as an unordered pool: reordering the same zones does not change a replica’s shape (see ReplicaShape::matches).

StateWrite

A durable state mutation a strategy’s update_state asks for: cut over the realized config to a target and/or write or clear the reconfiguration/burst records. The reconcile kernel pairs it with the ExpectedClusterState it was derived from for the compare-and-append guard.

Enums

ApplyOutcome

The outcome of applying one tick’s batch of Decisions.

Decision

A single command the controller emits for the environment to transact. The apply path interprets these and turns them into catalog operations.

Traits

ClusterControllerCtx

The strategy-agnostic pull/apply interface between the controller and its environment.