Crate ember_cluster 

ember-cluster: distributed coordination for ember.

This crate provides the building blocks for running ember as a distributed cluster with automatic failover and horizontal scaling.

Architecture

The cluster layer sits between the protocol layer and the storage engine, handling:

• Slot management: 16384 hash slots distributed across nodes
• Topology tracking: Node membership and health monitoring
• Failure detection: SWIM gossip protocol for quick detection
• Consensus: Raft for cluster configuration changes
• Migration: Live slot resharding without downtime

Quick Start

use ember_cluster::{ClusterState, ClusterNode, NodeId, key_slot};

// Create a single-node cluster
let node_id = NodeId::new();
let node = ClusterNode::new_primary(node_id, "127.0.0.1:6379".parse().unwrap());
let cluster = ClusterState::single_node(node);

// Route a key to its slot
let slot = key_slot(b"mykey");
assert!(cluster.owns_slot(slot));

Structs

BasicNode

An implementation of trait Node that contains minimal node information.

ClusterNode

Information about a single node in the cluster.

ClusterSecret

A shared secret used to authenticate cluster transport messages.

ClusterSnapshot

State machine snapshot.

ClusterState

The complete state of the cluster as seen by a node.

ClusterStateData

Internal cluster state managed by the state machine.

Election

State for an in-progress automatic failover election.

GossipConfig

Configuration for the gossip protocol.

GossipEngine

The gossip engine manages cluster membership and failure detection.

MemberInfo

Information about a cluster member.

MemberState

Internal state of a cluster member as tracked by gossip.

Migration

A single slot migration operation.

MigrationBatch

Represents a batch of keys to migrate.

MigrationConfig

Configuration for migration behavior.

MigrationEntry

A single key-value entry being migrated.

MigrationId

Unique identifier for a migration operation.

MigrationManager

Tracks all active migrations for a node.

NodeFlags

Status flags for a node.

NodeId

Unique identifier for a cluster node.

NodeInfo

Information about a cluster node.

RaftNetworkFactory

Factory that creates per-peer RaftNetworkClient instances.

RaftNode

High-level Raft node wrapper.

RaftStorage

Combined log and state machine storage for Raft.

SlotMap

Maps each of the 16384 slots to a node ID.

SlotRange

A contiguous range of slots assigned to a node.

TypeConfig

Type configuration for openraft.

Enums

ClusterCommand

Commands that modify cluster configuration.

ClusterError

Errors that can occur during cluster operations.

ClusterHealth

Overall cluster health status.

ClusterResponse

Response from applying a cluster command.

ConfigParseError

Error returned when parsing a nodes.conf file fails.

GossipEvent

Events emitted by the gossip engine.

GossipMessage

Message types for the SWIM gossip protocol.

MemberStatus

Health status of a member.

MigrationError

Errors that can occur during migration.

MigrationRedirect

Result of checking whether a command should be redirected during migration.

MigrationState

Current state of a slot migration.

NodeRole

The role of a node in the cluster.

NodeUpdate

A state update about a node, piggybacked on protocol messages.

RaftDiskError

RaftProposalError

Error from proposing a command through Raft.

Constants

SLOT_COUNT

Total number of hash slots in the cluster (Redis Cluster standard).

Functions

key_slot

Computes the hash slot for a key.

raft_id_from_node_id

Derives a stable u64 raft ID from a NodeId UUID.