Struct mz_compute_client::controller::instance::SharedCollectionState

pub(super) struct SharedCollectionState<T> {
    read_capabilities: Arc<Mutex<MutableAntichain<T>>>,
    write_frontier: Arc<Mutex<Antichain<T>>>,
}

Collection state shared with the ComputeController.

Having this allows certain controller APIs, such as ComputeController::collection_frontiers and ComputeController::acquire_read_hold to be non-async. This comes at the cost of complexity (by introducing shared mutable state) and performance (by introducing locking). We should aim to reduce the amount of shared state over time, rather than expand it.

Note that SharedCollectionStates are initialized by the ComputeController prior to the collection’s creation in the Instance. This is to allow compute clients to query frontiers and take new read holds immediately, without having to wait for the Instance to update.

Fields

read_capabilities: Arc<Mutex<MutableAntichain<T>>>

Accumulation of read capabilities for the collection.

This accumulation contains the capabilities held by all ReadHolds given out for the collection, including implied_read_hold and warmup_read_hold.

NOTE: This field may only be modified by Instance::apply_read_hold_changes and ComputeController::acquire_read_hold. Nobody else should modify read capabilities directly. Instead, collection users should manage read holds through ReadHold objects acquired through ComputeController::acquire_read_hold.

TODO(teskje): Restructure the code to enforce the above in the type system.

write_frontier: Arc<Mutex<Antichain<T>>>

The write frontier of this collection.

Implementations

impl<T: Timestamp> SharedCollectionState<T>

pub fn new(as_of: Antichain<T>) -> Self

pub fn lock_read_capabilities<F, R>(&self, f: F) -> R

where F: FnOnce(&mut MutableAntichain<T>) -> R,

pub fn lock_write_frontier<F, R>(&self, f: F) -> R

where F: FnOnce(&mut Antichain<T>) -> R,

Trait Implementations

impl<T: Clone> Clone for SharedCollectionState<T>

fn clone(&self) -> SharedCollectionState<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for SharedCollectionState<T>

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

Formats the value using the given formatter.