Struct InMemoryStorage 

pub struct InMemoryStorage { /* private fields */ }

Bounded in-memory cache storage.

Suitable for production reverse-proxy and client-side caching: byte-aware size cap, scan-resistant admission, and concurrent reads and writes on distinct keys without contention.

Defaults to a 256 MiB byte cap; override with with_max_capacity_bytes, unbounded, with_time_to_idle, and with_time_to_live. Each setter discards any previously inserted entries; configure at construction, before the storage is populated or shared.

Clone is cheap — clones share the same backing storage.

Granularity

Eviction is coarse: the unit is one CacheKey (method + URL), and all Vary variants stored under that key live and die together during eviction. In typical traffic patterns variants of the same URL are hot or cold together (a single Accept-Encoding is usually dominant, etc.), so the cost is bounded — at worst we keep a few cold variants resident alongside one hot variant. This is correct per RFC 9111; the only consequence is slightly less efficient use of memory than per-variant eviction would give.

Sizing

The byte cap is enforced over stored body bytes only (the dominant cost); headers and other metadata are not counted. The per-response cap on Cache::with_max_cacheable_size interacts independently — that one bounds how large any single response may be; the storage cap bounds total resident size across the cache.

Implementations

impl InMemoryStorage

pub fn new() -> Self

Construct an in-memory storage with default settings: a 256 MiB byte cap, no idle eviction, no TTL.

pub fn with_max_capacity_bytes(self, bytes: u64) -> Self

Set the maximum total stored body size, in bytes. Entries are evicted when inserts would exceed this cap. Defaults to 256 MiB.

pub fn unbounded(self) -> Self

Remove the size cap. The cache grows without bound. Useful in tests and short-lived processes; production deployments should prefer the default capped configuration.

pub fn with_time_to_idle(self, duration: Duration) -> Self

Evict entries that have not been read in this duration. Off by default.

pub fn with_time_to_live(self, duration: Duration) -> Self

Evict entries this duration after their last insert, regardless of access. Off by default.

Note: this is independent of RFC 9111 freshness — a stored entry may be evicted by TTL while still within its max-age/s-maxage window, or remain past it (the CachePolicy handles freshness on read).

pub fn entry_count(&self) -> u64

Approximate count of stored CacheKeys. Each key may hold multiple Vary variants. Eventually consistent — call run_pending_tasks first for a settled value (useful in tests).

pub fn weighted_size(&self) -> u64

Approximate total weighted size (sum of stored body bytes across all entries). Eventually consistent — call run_pending_tasks first for a settled value.

pub async fn run_pending_tasks(&self)

Flush pending eviction/insertion bookkeeping. Call before reading entry_count or weighted_size when an exact value matters.

Trait Implementations

impl CacheStorage for InMemoryStorage

type PutHandle = InMemoryPutHandle

Streaming writer returned by put.

type StoredEntry = InMemoryEntry

Concrete entry type returned by get.

async fn get(&self, key: &CacheKey) -> Vec<Self::StoredEntry>

Fetch all entries stored under key. Returns an empty vec when the key has no entries.

async fn put( &self, key: CacheKey, policy: CachePolicy, ) -> Result<Self::PutHandle>

Open a streaming insert for key with the supplied policy. Returns a PutHandle that the caller writes body bytes into, then closes with PutHandle::finalize. If an existing entry has the same Vary signature, finalize replaces it; otherwise the new entry is appended.

async fn invalidate(&self, key: &CacheKey)

Remove all entries stored under key.

impl Clone for InMemoryStorage

fn clone(&self) -> InMemoryStorage

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for InMemoryStorage

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

Formats the value using the given formatter.

impl Default for InMemoryStorage

fn default() -> Self

Returns the “default value” for a type.