Module vnode 

VnodeRegistry — runtime-configurable virtual node topology.

A registry owns:

• the runtime-selected vnode count,
• the node-per-vnode assignment (for distributed modes),
• a monotonically increasing assignment_version used to fence stale assignment publications.

Vnode assignment is derived from the row’s primary key via key_hash (xxh3) and modulo vnode_count. Connectors that need a vnode ID for an event call VnodeRegistry::vnode_for_key.

Structs

ArchivedNodeId

An archived NodeId

InvalidKeyGroupCount

A key-group count outside the supported 1..=65535 range.

KeyGroupCount

Validated number of stable key groups in a pipeline.

Locality

A node’s failure-domain locality: ordered tier values, coarsest first (e.g. ["us-east-1", "us-east-1a", "r17"]). Parsed from the node’s failure_domain gossip string.

NodeId

Unique identifier for a node. Also the owner id for vnodes; cluster membership and vnode ownership identify the same thing.

NodeIdResolver

The resolver for an archived NodeId

VnodeAssignmentReadGuard

Read guard that pins one assignment publication while a source captures a data batch or checkpoint cursor.

VnodeAssignmentSnapshot

One immutable publication of vnode ownership and its assignment version.

VnodeRegistry

Runtime registry of vnode topology and assignment.

Constants

DEFAULT_KEY_GROUP_COUNT

Default stable key-group count for every deployment tier.

LOCAL_NODE_ID

Stable owner identity for embedded and standalone runtimes.

MAX_KEY_GROUP_COUNT

Largest key-group count representable by the persisted checkpoint ABI.

PARTITIONING_ABI_VERSION

Durable encoding and hashing contract used to map keys to key groups.

Functions

key_hash

Hash a key to a 64-bit value. Used to derive vnode IDs and for any other keyed-partitioning decisions.

owned_vnodes

Vnodes currently assigned to owner.

owners_per_domain

Owner counts per failure domain at isolation_tier. The largest value over vnode_count is the blast radius — the share of state affected if that one domain fails at once.

peer_owners

Distinct assigned nodes other than self_id, sorted by id — the peer set a node fans checkpoint barriers and shuffle data out to.

rendezvous_assignment

Build a vnode-to-owner assignment using Rendezvous Hashing (Highest Random Weight).