HydraCache 0.51.0

HydraCache 0.51.0

0.51.0 adds configurable per-namespace and per-region persistence. It gives
HydraCache selective, opt-in durability: an on-disk value-store backend,
Hazelcast-style namespace policy, important-region selection, durable write
paths, scheduled snapshots, fail-loud full-cluster restart recovery, and
declarative configuration.

The release keeps RAM-only behavior as the default. Persistence is paid for only
where policy enables it.

Highlights

• Added the DurableValueStore on-disk backend for the value plane with
  checksummed, versioned records behind an opt-in feature.
• Added PersistencePolicy resolution with exact, wildcard, and prefix-style
  namespace matching.
• Added per-region persistence selection so only important regions/namespaces
  survive restart.
• Added sync and bounded-async durable write behavior for persistent namespaces.
• Added scheduled snapshot support for persistent data without changing the
  default in-memory path.
• Added fail-loud, epoch-fenced full-cluster restart recovery for persisted
  values.
• Added declarative persistence config and operator-surface metadata.
• Added deterministic simulator coverage for crash/restart, selective recovery,
  and stale-data fencing.

Verification

Focused gates:

cargo test -p hydracache --features durable-value-store --locked durable_value_store
cargo test -p hydracache --locked persistence_policy
cargo test -p hydracache --locked region_persistence
cargo test -p hydracache --features durable-value-store --locked durability_write_path
cargo test -p hydracache --features durable-value-store --locked persistence_recovery
cargo test -p hydracache --locked persistence_config
cargo test -p hydracache-sim --locked persistence_recovery

Full gate:

cargo xtask verify

Extended crash/restart soak remains a nightly/pre-release tier:

cargo test --workspace --locked -- --ignored

Scope Boundary

This is selective cache durability, not a database. HydraCache does not become a
source of truth, does not persist all namespaces by default, and does not hide
stale or corrupt recovery state. Operators still own snapshot storage, key
management, and persistence policy.

Release Status

Published as 0.51.0 after the persistence and simulator recovery gates.