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futurepool.rs
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futurepool.rs
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// Copyright 2018 PingCAP, Inc.
//
// 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 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,
// See the License for the specific language governing permissions and
// limitations under the License.
//! This mod implemented a wrapped future pool that supports `on_tick()` which
//! is invoked no less than the specific interval.
use std::cell::{Cell, RefCell, RefMut};
use std::fmt;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{mpsc, Arc};
use std::thread;
use std::time::Duration;
use futures::Future;
use futures_cpupool::{self as cpupool, CpuFuture, CpuPool};
use prometheus::{IntCounter, IntCounterVec, IntGauge, IntGaugeVec};
use crate::util;
use crate::util::collections::HashMap;
use crate::util::time::Instant;
lazy_static! {
pub static ref FUTUREPOOL_PENDING_TASK_VEC: IntGaugeVec = register_int_gauge_vec!(
"tikv_futurepool_pending_task_total",
"Current future_pool pending + running tasks.",
&["name"]
)
.unwrap();
pub static ref FUTUREPOOL_HANDLED_TASK_VEC: IntCounterVec = register_int_counter_vec!(
"tikv_futurepool_handled_task_total",
"Total number of future_pool handled tasks.",
&["name"]
)
.unwrap();
}
pub trait Context: fmt::Debug + Send {
/// Will be invoked periodically (no less than specified interval).
/// When there is no task, it will NOT be invoked.
fn on_tick(&mut self) {}
}
/// A delegator to wrap `Context` to provide `on_tick` feature.
#[derive(Debug)]
struct ContextDelegator<T: Context> {
tick_interval: Duration,
inner: RefCell<T>,
last_tick: Cell<Option<Instant>>,
}
impl<T: Context> ContextDelegator<T> {
fn new(context: T, tick_interval: Duration) -> ContextDelegator<T> {
ContextDelegator {
tick_interval,
inner: RefCell::new(context),
last_tick: Cell::new(None),
}
}
fn context_mut(&self) -> RefMut<T> {
self.inner.borrow_mut()
}
fn on_task_finish(&self) {
let now = Instant::now_coarse();
let last_tick = self.last_tick.get();
if last_tick.is_none() {
// set last_tick when the first future is resolved
self.last_tick.set(Some(now));
return;
}
if now.duration_since(last_tick.unwrap()) < self.tick_interval {
return;
}
self.last_tick.set(Some(now));
self.context_mut().on_tick();
}
}
#[derive(Debug)]
pub struct ContextDelegators<T: Context> {
delegators: Arc<HashMap<thread::ThreadId, ContextDelegator<T>>>,
}
/// Users can only retrive a Context for the current thread so that `HashMap<..>` is `Sync`.
/// Thus `ContextDelegators` is `Send` & `Sync`.
unsafe impl<T: Context> Send for ContextDelegators<T> {}
unsafe impl<T: Context> Sync for ContextDelegators<T> {}
impl<T: Context> Clone for ContextDelegators<T> {
fn clone(&self) -> Self {
ContextDelegators {
delegators: Arc::clone(&self.delegators),
}
}
}
impl<T: Context> ContextDelegators<T> {
fn new(delegators: HashMap<thread::ThreadId, ContextDelegator<T>>) -> Self {
ContextDelegators {
delegators: Arc::new(delegators),
}
}
/// This function should be called in the future pool thread. Otherwise it will panic.
pub fn current_thread_context_mut(&self) -> RefMut<T> {
let delegator = self.get_current_thread_delegator();
delegator.context_mut()
}
fn get_current_thread_delegator(&self) -> &ContextDelegator<T> {
let thread_id = thread::current().id();
if let Some(delegator) = self.delegators.get(&thread_id) {
delegator
} else {
panic!("Called from threads out of the future thread pool");
}
}
}
/// A future thread pool that supports `on_tick` for each thread.
pub struct FuturePool<T: Context + 'static> {
pool: CpuPool,
context_delegators: ContextDelegators<T>,
running_task_count: Arc<AtomicUsize>,
metrics_pending_task_count: IntGauge,
metrics_handled_task_count: IntCounter,
}
impl<T: Context + 'static> fmt::Debug for FuturePool<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
f.debug_struct("FuturePool")
.field("pool", &self.pool)
.field("context_delegators", &self.context_delegators)
.finish()
}
}
impl<T: Context + 'static> Clone for FuturePool<T> {
fn clone(&self) -> FuturePool<T> {
FuturePool {
pool: self.pool.clone(),
context_delegators: self.context_delegators.clone(),
running_task_count: Arc::clone(&self.running_task_count),
metrics_pending_task_count: self.metrics_pending_task_count.clone(),
metrics_handled_task_count: self.metrics_handled_task_count.clone(),
}
}
}
impl<T: Context + 'static> util::AssertSend for FuturePool<T> {}
impl<T: Context + 'static> util::AssertSync for FuturePool<T> {}
impl<T: Context + 'static> FuturePool<T> {
pub fn new<F>(
pool_size: usize,
stack_size: usize,
name_prefix: &str,
tick_interval: Duration,
context_factory: F,
) -> FuturePool<T>
where
F: Fn() -> T,
{
let (tx, rx) = mpsc::sync_channel(pool_size);
let pool = cpupool::Builder::new()
.pool_size(pool_size)
.stack_size(stack_size)
.name_prefix(name_prefix)
.after_start(move || {
// We only need to know each thread's id and we can build context later
// by invoking `context_factory` in a non-concurrent way.
let thread_id = thread::current().id();
tx.send(thread_id).unwrap();
})
.create();
let contexts = (0..pool_size)
.map(|_| {
let thread_id = rx.recv().unwrap();
let context_delegator = ContextDelegator::new(context_factory(), tick_interval);
(thread_id, context_delegator)
})
.collect();
FuturePool {
pool,
context_delegators: ContextDelegators::new(contexts),
running_task_count: Arc::new(AtomicUsize::new(0)),
metrics_pending_task_count: FUTUREPOOL_PENDING_TASK_VEC
.with_label_values(&[name_prefix]),
metrics_handled_task_count: FUTUREPOOL_HANDLED_TASK_VEC
.with_label_values(&[name_prefix]),
}
}
/// Gets current running task count
#[inline]
pub fn get_running_task_count(&self) -> usize {
self.running_task_count.load(Ordering::Acquire)
}
pub fn spawn<F, R>(&self, future_factory: R) -> CpuFuture<F::Item, F::Error>
where
R: FnOnce(ContextDelegators<T>) -> F + Send + 'static,
F: Future + Send + 'static,
F::Item: Send + 'static,
F::Error: Send + 'static,
{
let running_task_count = Arc::clone(&self.running_task_count);
let metrics_pending_task_count = self.metrics_pending_task_count.clone();
let metrics_handled_task_count = self.metrics_handled_task_count.clone();
let delegators = self.context_delegators.clone();
let func = move || {
future_factory(delegators.clone()).then(move |r| {
let delegator = delegators.get_current_thread_delegator();
delegator.on_task_finish();
running_task_count.fetch_sub(1, Ordering::Release);
metrics_pending_task_count.dec();
metrics_handled_task_count.inc();
r
})
};
self.running_task_count.fetch_add(1, Ordering::Release);
self.metrics_pending_task_count.inc();
self.pool.spawn_fn(func)
}
}
#[cfg(test)]
mod tests {
use futures::future;
use std::sync::mpsc::{channel, Sender};
use std::thread;
use std::time::Duration;
pub use super::*;
fn spawn_long_time_future<T: Context>(
pool: &FuturePool<T>,
future_duration_ms: u64,
) -> CpuFuture<(), ()> {
pool.spawn(move |_| {
thread::sleep(Duration::from_millis(future_duration_ms));
future::ok::<(), ()>(())
})
}
fn spawn_long_time_future_and_wait<T: Context>(pool: &FuturePool<T>, future_duration_ms: u64) {
spawn_long_time_future(pool, future_duration_ms)
.wait()
.unwrap();
}
#[test]
fn test_context() {
#[derive(Debug)]
struct MyContext {
ctx_thread_id: thread::ThreadId,
}
impl Context for MyContext {}
let pool = FuturePool::new(
1,
1024000,
"test-pool",
Duration::from_millis(50),
move || MyContext {
ctx_thread_id: thread::current().id(),
},
);
let main_thread_id = thread::current().id();
pool.spawn(move |ctxd| {
// future_factory is executed in future pool
let current_thread_id = thread::current().id();
assert_ne!(main_thread_id, current_thread_id);
// Context is created in main thread
let ctx = ctxd.current_thread_context_mut();
assert_eq!(ctx.ctx_thread_id, main_thread_id);
future::ok::<(), ()>(())
})
.wait()
.unwrap();
}
#[test]
fn test_tick() {
struct MyContext {
tx: Sender<i32>,
sn: i32,
}
impl fmt::Debug for MyContext {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "MyContext")
}
}
impl Context for MyContext {
fn on_tick(&mut self) {
self.tx.send(self.sn).unwrap();
self.sn += 1;
}
}
let (tx, rx) = channel();
let pool = FuturePool::new(
1,
1024000,
"test-pool",
Duration::from_millis(200),
move || MyContext {
tx: tx.clone(),
sn: 0,
},
);
assert!(rx.try_recv().is_err());
// Tick is not emitted since there is no task
thread::sleep(Duration::from_millis(400));
assert!(rx.try_recv().is_err());
// Tick is not emitted immediately for the first future
spawn_long_time_future_and_wait(&pool, 10);
assert!(rx.try_recv().is_err());
spawn_long_time_future_and_wait(&pool, 1);
spawn_long_time_future_and_wait(&pool, 1);
spawn_long_time_future_and_wait(&pool, 1);
spawn_long_time_future_and_wait(&pool, 1);
assert!(rx.try_recv().is_err());
// Even if there are tasks previously, tick is not emitted until next task arrives
thread::sleep(Duration::from_millis(400));
assert!(rx.try_recv().is_err());
// Next task arrives && long time passed, tick is emitted
spawn_long_time_future_and_wait(&pool, 400);
assert_eq!(rx.try_recv().unwrap(), 0);
assert!(rx.try_recv().is_err());
// Tick is not emitted if there is no task
thread::sleep(Duration::from_millis(400));
assert!(rx.try_recv().is_err());
// Tick is emitted since long enough time has passed
spawn_long_time_future_and_wait(&pool, 1);
assert_eq!(rx.try_recv().unwrap(), 1);
assert!(rx.try_recv().is_err());
}
#[test]
fn test_task_count() {
#[derive(Debug)]
struct MyContext;
impl Context for MyContext {}
let pool = FuturePool::new(
2,
1024000,
"test-pool",
Duration::from_millis(50),
move || MyContext {},
);
assert_eq!(pool.get_running_task_count(), 0);
let f1 = spawn_long_time_future(&pool, 100);
assert_eq!(pool.get_running_task_count(), 1);
let f2 = spawn_long_time_future(&pool, 200);
assert_eq!(pool.get_running_task_count(), 2);
let f3 = spawn_long_time_future(&pool, 300);
assert_eq!(pool.get_running_task_count(), 3);
f1.wait().unwrap();
assert_eq!(pool.get_running_task_count(), 2);
let f4 = spawn_long_time_future(&pool, 300);
let f5 = spawn_long_time_future(&pool, 300);
assert_eq!(pool.get_running_task_count(), 4);
f2.join(f3).wait().unwrap();
assert_eq!(pool.get_running_task_count(), 2);
f4.join(f5).wait().unwrap();
assert_eq!(pool.get_running_task_count(), 0);
}
}