Struct FileScheduler 

pub struct FileScheduler { /* private fields */ }

A throttled file reader

Implementations

impl FileScheduler

pub fn submit_request( &self, request: Vec<Range<u64>>, priority: u64, ) -> impl Future<Output = Result<Vec<Bytes>>> + Send + use<>

Submit a batch of I/O requests to the reader

The requests will be queued in a FIFO manner and, when all requests have been fulfilled, the returned future will be completed.

Each request has a given priority. If the I/O loop is full then requests will be buffered and requests with the lowest priority will be released from the buffer first.

Each request has a backpressure ID which controls which backpressure throttle is applied to the request. Requests made to the same backpressure throttle will be throttled together.

Ranges must be sorted by their start offset.

pub fn with_priority(&self, priority: u64) -> Self

pub fn with_io_stats(&self, stats: Arc<dyn IoStatsRecorder>) -> Self

Returns a copy of this scheduler that additionally records the I/O it performs into stats, on top of the scheduler’s global statistics.

This is the mechanism for measuring exact per-scope (e.g. per-query) I/O: attach a recorder here (e.g. via IoStats::recorder), perform the reads through the returned handle, then read the totals back with IoStats::snapshot. The returned handle is cheap to create (a few Arc clones) and reuses the same underlying reader, so it does not re-open the file.

pub fn with_bypass_backpressure(&self) -> Self

Returns a copy of this scheduler that bypasses backpressure for all requests.

This should be used for indirect I/O (e.g. fetching items after decoding offsets) where blocking on backpressure could cause a deadlock or excessive latency.

pub fn submit_single( &self, range: Range<u64>, priority: u64, ) -> impl Future<Output = Result<Bytes>> + Send

Submit a single IOP to the reader

If you have multiple IOPS to perform then Self::submit_request is going to be more efficient.

See Self::submit_request for more information on the priority and backpressure.

pub fn reader(&self) -> &Arc<dyn Reader>

Provides access to the underlying reader

Do not use this for reading data as it will bypass any I/O scheduling! This is mainly exposed to allow metadata operations (e.g size, block_size,) which either aren’t IOPS or we don’t throttle

Trait Implementations

impl Clone for FileScheduler

fn clone(&self) -> FileScheduler

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FileScheduler

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

Formats the value using the given formatter.