Struct mz_persist::indexed::cache::BlobCache

pub struct BlobCache<B> { /* private fields */ }

A disk-backed cache for objects in Blob storage.

The data for the objects in the cache is stored on disk, mmap’d, and a validated handle is stored in-memory to avoid repeatedly decoding it.

TODO: Add a limit to bound how much disk this cache can use. The Arc return type for get_batch seems correct, but means that a bad user could starve the cache by indefinitely holding handles. The Arcs could be made into weak references so the cache could forcefully reclaim the backing data, but this is going to make performance of using the cached batches unpredictable. I think we probably want a soft limit and a hard limit where the soft limit does some alerting and the hard limit starts blocking (or erroring) until disk space frees up.

Implementations

impl<B: Blob + Send + Sync + 'static> BlobCache<B>

pub fn new(
    metrics: Arc<Metrics>,
    blob: B,
    cache_size_limit: Option<usize>
) -> Self

Returns a new, empty cache for the given Blob storage.

pub async fn get_trace_batch_async(
    &self,
    key: &str,
    hint: CacheHint
) -> Result<Arc<BlobTraceBatchPart>, Error>

Asynchronously returns the batch for the given key, fetching in another thread if it’s not already in the cache.

impl<B: Blob + Send + Sync + 'static> BlobCache<B>

pub async fn set_trace_batch(
    &self,
    key: String,
    batch: BlobTraceBatchPart,
    format: ProtoBatchFormat
) -> Result<u64, Error>

Writes a batch to backing Blob storage.

Returns the size of the encoded blob value in bytes.

pub async fn delete_trace_batch(
    &mut self,
    batch: &TraceBatchMeta
) -> Result<(), Error>

Removes a batch from both Blob storage and the local cache.

Trait Implementations

impl<B> Clone for BlobCache<B>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<B: Debug> Debug for BlobCache<B>

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

Formats the value using the given formatter.