mz_timely_util/replay.rs
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// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file at the
// root of this repository, or online at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Traits and types for replaying captured timely dataflow streams.
//!
//! This is roughly based on [timely::dataflow::operators::capture::Replay], which
//! provides the protocol and semantics of the [MzReplay] operator.
use std::any::Any;
use std::borrow::Cow;
use std::rc::Rc;
use std::time::{Duration, Instant};
use timely::container::ContainerBuilder;
use timely::dataflow::channels::pushers::buffer::{Buffer as PushBuffer, Session};
use timely::dataflow::channels::pushers::{Counter as PushCounter, Tee};
use timely::dataflow::operators::capture::event::EventIterator;
use timely::dataflow::operators::capture::Event;
use timely::dataflow::operators::generic::builder_raw::OperatorBuilder;
use timely::dataflow::{Scope, StreamCore};
use timely::progress::Timestamp;
use timely::scheduling::ActivateOnDrop;
use timely::Container;
use crate::activator::ActivatorTrait;
/// Replay a capture stream into a scope with the same timestamp.
pub trait MzReplay<T, C, A>: Sized
where
T: Timestamp,
A: ActivatorTrait,
{
/// Replays `self` into the provided scope, as a `StreamCore<S, CB::Container>` and provides
/// a cancellation token. Uses the supplied container builder `CB` to form containers.
///
/// The `period` argument allows the specification of a re-activation period, where the operator
/// will re-activate itself every so often.
///
/// * `scope`: The [Scope] to replay into.
/// * `name`: Human-readable debug name of the Timely operator.
/// * `period`: Reschedule the operator once the period has elapsed.
/// Provide [Duration::MAX] to disable periodic scheduling.
/// * `activator`: An activator to trigger the operator.
fn mz_replay<S: Scope<Timestamp = T>, CB, L>(
self,
scope: &mut S,
name: &str,
period: Duration,
activator: A,
logic: L,
) -> (StreamCore<S, CB::Container>, Rc<dyn Any>)
where
CB: ContainerBuilder,
L: FnMut(Session<T, CB, PushCounter<T, CB::Container, Tee<T, CB::Container>>>, Cow<C>)
+ 'static;
}
impl<T, C, I, A> MzReplay<T, C, A> for I
where
T: Timestamp,
C: Container + Clone,
I: IntoIterator,
I::Item: EventIterator<T, C> + 'static,
A: ActivatorTrait + 'static,
{
fn mz_replay<S: Scope<Timestamp = T>, CB, L>(
self,
scope: &mut S,
name: &str,
period: Duration,
activator: A,
mut logic: L,
) -> (StreamCore<S, CB::Container>, Rc<dyn Any>)
where
for<'a> CB: ContainerBuilder,
L: FnMut(Session<T, CB, PushCounter<T, CB::Container, Tee<T, CB::Container>>>, Cow<C>)
+ 'static,
{
let name = format!("Replay {}", name);
let mut builder = OperatorBuilder::new(name, scope.clone());
let address = builder.operator_info().address;
let periodic_activator = scope.activator_for(Rc::clone(&address));
let (targets, stream) = builder.new_output();
let mut output: PushBuffer<_, CB, _> = PushBuffer::new(PushCounter::new(targets));
let mut event_streams = self.into_iter().collect::<Vec<_>>();
let mut started = false;
let mut last_active = Instant::now();
let mut progress_sofar =
<timely::progress::ChangeBatch<_>>::new_from(S::Timestamp::minimum(), 1);
let token = Rc::new(ActivateOnDrop::new(
(),
Rc::clone(&address),
scope.activations(),
));
let weak_token = Rc::downgrade(&token);
activator.register(scope, address);
builder.build(move |progress| {
activator.ack();
if last_active
.checked_add(period)
.map_or(false, |next_active| next_active <= Instant::now())
|| !started
{
last_active = Instant::now();
if period < Duration::MAX {
periodic_activator.activate_after(period);
}
}
if !started {
// The first thing we do is modify our capabilities to match the number of streams we manage.
// This should be a simple change of `self.event_streams.len() - 1`. We only do this once, as
// our very first action.
let len: i64 = event_streams
.len()
.try_into()
.expect("Implausibly large vector");
progress.internals[0].update(S::Timestamp::minimum(), len - 1);
progress_sofar.update(S::Timestamp::minimum(), len);
started = true;
}
if weak_token.upgrade().is_some() {
for event_stream in event_streams.iter_mut() {
while let Some(event) = event_stream.next() {
use Cow::*;
match event {
Owned(Event::Progress(vec)) => {
progress.internals[0].extend(vec.iter().cloned());
progress_sofar.extend(vec.into_iter());
}
Owned(Event::Messages(time, data)) => {
logic(output.session_with_builder(&time), Owned(data));
}
Borrowed(Event::Progress(vec)) => {
progress.internals[0].extend(vec.iter().cloned());
progress_sofar.extend(vec.iter().cloned());
}
Borrowed(Event::Messages(time, data)) => {
logic(output.session_with_builder(time), Borrowed(data));
}
}
}
}
} else {
// Negate the accumulated progress contents emitted so far.
progress.internals[0]
.extend(progress_sofar.drain().map(|(time, diff)| (time, -diff)));
}
output.cease();
output
.inner()
.produced()
.borrow_mut()
.drain_into(&mut progress.produceds[0]);
false
});
(stream, token)
}
}