HydraCache 0.42.0

HydraCache 0.42.0

0.42.0 hardens the distributed cache grid slice introduced in 0.41.0.
The release adds deterministic production-grid primitives, focused release-gate
tests, compatibility registrations, and operator artifacts. It still does not
add distributed transactions, KMS ownership, TLS/certificate lifecycle
management, or multi-region / zone-aware placement.

Highlights

• Added durable-log raft control-plane support:
  DurableRaftLogDirectory, DurableRaftLogStore,
  DurableControlPlaneCluster, and RAFT_LOG_FORMAT_VERSION.
• Added durable replicated value records:
  ReplicatedValueRecord, ReplicatedValueStore,
  InMemoryReplicatedValueStore, ValueVersion, SealedBytes, and
  REPLICATED_VALUE_RECORD_FORMAT_VERSION.
• Added production replication/failover helpers:
  AdaptiveWindow and PromotionFreezeWindow.
• Added split-brain merge primitives:
  SplitBrainReport, MergePolicy, HigherVersionWins, PutIfAbsent,
  DiscardLoser, merge_split_brain_records, and split_brain_winner.
• Added grid-wide read-your-writes helpers:
  WriteWatermark, ReadConsistency, QuorumPosture,
  quorum_read_your_writes, and ReplicationConfig::is_strong_ryow().
• Added cluster-route auth primitives in hydracache-cluster-transport-axum:
  NodeIdentityProvider, StaticNodeIdentityProvider, Authorizer,
  ClusterRouteAuth, credential rotation support, and explicit insecure
  trust-boundary acknowledgement.
• Added operator surface in hydracache-observability:
  ClusterStatus, MemberStatus, RepairDebtController, and
  RepairDebtMode.
• Shipped dashboards/alerts/runbook artifacts under docs/cluster/.

Verification

Focused gates:

cargo test -p hydracache-cluster-raft --locked durable_control_plane
cargo test -p hydracache-cluster-raft --locked --features durable-log durable_control_plane
cargo test -p hydracache --locked durable_replicated_values
cargo test -p hydracache --locked replication_under_load
cargo test -p hydracache --locked split_brain
cargo test -p hydracache --locked read_your_writes
cargo test -p hydracache-cluster-transport-axum --locked cluster_auth
cargo test -p hydracache-observability --locked operational_surface
cargo test -p hydracache --locked fault_injector_selftest

Full gates:

cargo fmt --all -- --check
cargo check --workspace --all-targets --locked
cargo test --workspace --all-targets --locked
cargo test --workspace --all-targets --locked --features durable-log,durable-values
cargo test --workspace --locked -- --ignored
cargo test --doc --workspace --locked
$env:RUSTDOCFLAGS = "-D warnings"; cargo doc --workspace --no-deps --locked

Scope Boundary

This release strengthens the single-topology grid path. It does not make
HydraCache a distributed transaction coordinator, a KMS, a TLS terminator, or a
multi-region placement system. Those boundaries remain explicit in cluster docs.