Crate amalgam 

amalgam — a robust, multi-level, fail-safe cache for Rust.

An amalgam is a fusion of metals; this crate is a faithful, idiomatic Rust port of the resiliency model pioneered by .NET’s FusionCache. It fuses an in-memory L1 cache with an optional distributed L2 cache and gives you the features that make a cache robust rather than merely fast:

• Cache-stampede protection — only one factory runs per key (single-flight).
• Fail-safe — serve a stale value when the factory fails, instead of erroring.
• Soft / hard timeouts — a slow factory can return a stale value immediately and finish in the background.
• Eager refresh — refresh proactively before expiration, off the hot path.
• Adaptive caching — the factory can change the entry’s options per call.
• Conditional refresh — HTTP-style NotModified reuse of a stale value.
• Tagging — invalidate many entries at once, lazily, by tag.
• L1 + L2 + backplane — pluggable distributed cache and multi-node sync.

See PORTING.md for the C#→Rust translation methodology and docs/PARITY.md for the feature-by-feature mapping to FusionCache.

Re-exports

pub use backplane::Backplane;

pub use backplane::BackplaneAction;

pub use backplane::BackplaneMessage;

pub use backplane::InProcessBackplane;

pub use cache::Cache;

pub use cache::CacheBuilder;

pub use circuit::CircuitBreaker;

pub use distributed::DistributedCache;

pub use distributed::DistributedEntry;

pub use distributed::DistributedSerializer;

pub use distributed::InMemoryDistributedCache;

pub use distributed::JsonSerializer;

pub use distributed_lock::DistributedLocker;

pub use distributed_lock::InMemoryDistributedLocker;

pub use error::Error;

pub use error::FactoryError;

pub use error::Result;

pub use events::CacheEvent;

pub use events::CircuitComponent;

pub use events::Events;

pub use factory::FactoryContext;

pub use factory::FactoryProduct;

pub use factory::ModifiedBuilder;

pub use maybe::MaybeValue;

pub use options::EagerThreshold;

pub use options::EntryOptions;

pub use options::KeyModifierMode;

pub use options::Priority;

pub use options::RemoveByTagBehavior;

pub use plugins::Plugin;

pub use plugins::PluginHost;

pub use recovery::AutoRecoveryService;

pub use recovery::RecoveryAction;

pub use recovery::RecoveryConfig;

pub use recovery::RecoveryExecutor;

pub use recovery::RecoveryItem;

pub use registry::CacheRegistry;

pub use registry::DefaultEntryOptionsProvider;

pub use tags::Tag;

pub use time::Clock;

pub use time::ManualClock;

pub use time::SystemClock;

pub use time::Timeout;

pub use time::Timestamp;

Modules

backplane

The backplane: multi-node invalidation messaging.

cache

The Cache type — the heart of the library.

circuit

A circuit breaker for L2 / backplane operations.

distributed

L2 distributed cache: the wire envelope, a serializer abstraction, the DistributedCache backend trait, and an in-memory reference backend.

distributed_lock

Cross-node single-flight: the DistributedLocker seam.

entry

The internal cache entry envelope: value plus the metadata that drives freshness, fail-safe and eager-refresh decisions.

error

Error types.

events

The event hub.

factory

The factory execution context and its product.

locking

Single-flight locking for cache-stampede protection.

maybe

The MaybeValue type: “a value, or explicitly no value”.

memory

The L1 (in-memory) store, backed by moka.

observability

Metrics, exposed as a Plugin (feature metrics).

options

Per-entry options (EntryOptions) and their supporting value types.

plugins

The plugin seam.

recovery

Auto-recovery: retry L2 / backplane operations that failed transiently.

registry

Named caches and dynamic default options.

serializers

Additional L2 serializers behind feature flags.

tags

Tagging: Tag values and the lazy TagRegistry that powers Cache::remove_by_tag and Cache::clear.

time

Time abstractions.