Struct RemoteIndexCache 

pub struct RemoteIndexCache { /* private fields */ }

A bounded on-disk cache of remote segment index objects.

Implementations

impl RemoteIndexCache

pub fn new(log_dir: &Path, max_bytes: u64) -> Result<Self, RemoteStorageError>

Opens (and empties) <log_dir>/remote-log-index-cache and returns a cache bounded by max_bytes.

Errors

Returns RemoteStorageError::Io when the directory cannot be emptied or created.

pub fn disabled() -> Self

A cache that stores nothing: every lookup runs the fetcher and reports IndexCacheOutcome::Disabled.

pub fn is_enabled(&self) -> bool

Whether this cache stores anything.

pub fn max_bytes(&self) -> u64

The current total-byte budget.

pub fn resize(&self, max_bytes: u64)

Sets the total-byte budget to max_bytes, evicting the least-recently-used entries until the held bytes fit it.

This is Kafka’s RemoteIndexCache.resizeCacheSize, which sets the Caffeine maximum weight and so evicts down to the new size at once. A grow evicts nothing. A disabled cache only records the new budget.

pub fn stats(&self) -> IndexCacheStats

The counters the broker publishes.

pub fn get_or_fetch<F>( &self, segment_id: Uuid, index_type: IndexType, fetch: F, ) -> Result<(Vec<u8>, IndexCacheOutcome), RemoteStorageError>

where F: FnOnce() -> Result<Vec<u8>, RemoteStorageError>,

Returns segment_id’s index_type bytes, running fetch only when the cache does not already hold them.

fetch is called outside the cache lock, so several partitions can miss concurrently. Two concurrent misses on the same key both download and the second write replaces the first with identical bytes; a remote index object is immutable once its segment is finished, so the race costs one extra download and never returns the wrong bytes.

Errors

Returns whatever fetch returns on a miss. A cache-directory failure is not an error: the fetched bytes are returned and the entry is simply not stored.

pub fn remove_segment(&self, segment_id: Uuid)

Drops every cached index of segment_id.

The RemoteLogManager calls this when a segment enters DeleteSegmentStarted, so the deleted segment’s bytes stop counting against the budget.

Trait Implementations

impl Debug for RemoteIndexCache

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

Formats the value using the given formatter.