Struct DefaultShardExtractor 

pub struct DefaultShardExtractor { /* private fields */ }

Hash-based default extractor: FNV-1a 64-bit (entity_id) % num_shards.

Cross-node shard stability contract

The FNV-1a 64-bit hash used here is version-stable forever (public-domain constants). Every Datum node that runs the same num_shards MUST produce identical shard_id values for the same entity_id, regardless of Rust compiler version, target OS/arch, or Datum release. This prevents split-entity faults in mixed-version clusters during rolling upgrades. The golden test golden_shard_map_is_stable pins known entity-id-to-shard mappings; any hash change will fail that test loudly.

A one-time re-mapping of existing entities onto new shards after the switch from std::DefaultHasher (SipHash) to FNV-1a is expected and acceptable pre-1.0.

Implementations

impl DefaultShardExtractor

pub fn new(num_shards: u64) -> Self

Create a default extractor with num_shards.

pub const fn num_shards(&self) -> u64

Configured shard count.

Trait Implementations

impl Clone for DefaultShardExtractor

fn clone(&self) -> DefaultShardExtractor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DefaultShardExtractor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<M> ShardExtractor<M> for DefaultShardExtractor

fn shard_id(&self, entity_id: &str) -> String

Return the shard id for entity_id.

fn entity_id<'a>(&self, envelope: &'a ShardEnvelope<M>) -> &'a str

Return the entity id for envelope.