Struct mz_persist_client::read::Listen

pub struct Listen<K: Codec, V: Codec, T, D> {
    handle: ReadHandle<K, V, T, D>,
    watch: StateWatch<K, V, T, D>,
    as_of: Antichain<T>,
    since: Antichain<T>,
    frontier: Antichain<T>,
}

An ongoing subscription of updates to a shard.

Fields

handle: ReadHandle<K, V, T, D>

watch: StateWatch<K, V, T, D>

as_of: Antichain<T>

since: Antichain<T>

frontier: Antichain<T>

Implementations

impl<K, V, T, D> Listen<K, V, T, D>

where K: Debug + Codec, V: Debug + Codec, T: Timestamp + Lattice + Codec64 + Sync, D: Semigroup + Codec64 + Send + Sync,

async fn new(handle: ReadHandle<K, V, T, D>, as_of: Antichain<T>) -> Self

pub fn frontier(&self) -> &Antichain<T>

An exclusive upper bound on the progress of this Listen.

pub async fn next( &mut self, retry: Option<RetryParameters>, ) -> (Vec<LeasedBatchPart<T>>, Antichain<T>)

Attempt to pull out the next values of this subscription.

The returned LeasedBatchPart is appropriate to use with crate::fetch::fetch_leased_part.

The returned Antichain represents the subscription progress as it will be after the returned parts are fetched.

impl<K, V, T, D> Listen<K, V, T, D>

where K: Debug + Codec, V: Debug + Codec, T: Timestamp + Lattice + Codec64 + Sync, D: Semigroup + Codec64 + Send + Sync,

pub async fn fetch_next( &mut self, ) -> Vec<ListenEvent<T, ((Result<K, String>, Result<V, String>), T, D)>>

Attempt to pull out the next values of this subscription.

The updates received in ListenEvent::Updates should be assumed to be in arbitrary order and not necessarily consolidated. However, the timestamp of each individual update will be greater than or equal to the last received ListenEvent::Progress frontier (or this Listen’s initial as_of frontier if no progress event has been emitted yet) and less than the next ListenEvent::Progress frontier.

If you have a use for consolidated listen output, given that snapshots can’t be consolidated, come talk to us!

pub fn into_stream( self, ) -> impl Stream<Item = ListenEvent<T, ((Result<K, String>, Result<V, String>), T, D)>>

Convert listener into futures::Stream

impl<K, V, T, D> Listen<K, V, T, D>

where K: Debug + Codec, V: Debug + Codec, T: Timestamp + Lattice + Codec64 + Sync, D: Semigroup + Codec64 + Send + Sync,

async fn fetch_batch_part( &mut self, part: LeasedBatchPart<T>, ) -> FetchedPart<K, V, T, D>

Fetches the contents of part and returns its lease.

This is broken out into its own function to provide a trivial means for Subscribe, which contains a Listen, to fetch batches.

pub async fn expire(self)

Politely expires this listen, releasing its lease.

There is a best-effort impl in Drop for ReadHandle to expire the ReadHandle held by the listen that wasn’t explicitly expired with this method. When possible, explicit expiry is still preferred because the Drop one is best effort and is dependant on a tokio Handle being available in the TLC at the time of drop (which is a bit subtle). Also, explicit expiry allows for control over when it happens.

Trait Implementations

impl<K: Debug + Codec, V: Debug + Codec, T: Debug, D: Debug> Debug for Listen<K, V, T, D>

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

Formats the value using the given formatter.