Struct ElasticShardSet 

pub struct ElasticShardSet<K, V> { /* private fields */ }

A set of shards that can grow and shrink at runtime.

Each shard is a FabricHashMap backed by its own grafos_std::mem::MemLease. Keys are routed to shards via hash(key) % shard_count.

Example

use grafos_cache::elastic::ElasticShardSet;

let mut shards: ElasticShardSet<u32, u32> =
    ElasticShardSet::new(2, 64, 8, 8)?;

shards.put(&1, &100)?;
shards.put(&2, &200)?;
assert_eq!(shards.get(&1)?, Some(100));
assert_eq!(shards.shard_count(), 2);

// Grow by one shard and redistribute
shards.add_shard()?;
shards.rehash()?;
assert_eq!(shards.shard_count(), 3);
assert_eq!(shards.get(&1)?, Some(100));

Implementations

impl<K, V> ElasticShardSet<K, V>

where K: Serialize + DeserializeOwned + PartialEq + Clone, V: Serialize + DeserializeOwned + Clone,

pub fn new( initial_shards: usize, buckets_per_shard: usize, key_stride: usize, val_stride: usize, ) -> Result<Self>

Create a new shard set with initial_shards shards.

Each shard is a FabricHashMap allocated via grafos_std::mem::MemBuilder with buckets_per_shard buckets. key_stride and val_stride control the maximum serialized size of keys and values respectively.

Errors

Returns FabricError::CapacityExceeded if the host cannot provide enough memory for the requested shards.

pub fn get(&self, key: &K) -> Result<Option<V>>

Look up a value by key.

Hashes the key to select the correct shard, then performs a lookup within that shard.

pub fn put(&mut self, key: &K, value: &V) -> Result<()>

Insert or update a key-value pair.

Hashes the key to select the correct shard, then inserts into that shard.

pub fn remove(&mut self, key: &K) -> Result<bool>

Remove a key-value pair. Returns true if the key existed.

pub fn add_shard(&mut self) -> Result<()>

Add one shard to the set.

The new shard is empty. Call rehash afterwards to redistribute existing entries across all shards.

pub fn remove_shard(&mut self) -> Result<()>

Remove the last shard from the set.

All entries across every shard are drained and redistributed among the remaining shards (since hash % shard_count changes for all keys when the shard count changes). The removed shard’s lease is released on drop.

Errors

Returns FabricError::CapacityExceeded if the set has only one shard (cannot shrink below 1).

pub fn rehash(&mut self) -> Result<()>

Redistribute all entries across the current shard set.

Drains every shard, then re-inserts all entries using the current shard count. This is useful after add_shard to balance load.

pub fn shard_count(&self) -> usize

Number of shards in the set.

pub fn len(&self) -> Result<usize>

Total number of entries across all shards.

pub fn is_empty(&self) -> Result<bool>

Returns true if no entries exist across all shards.