use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, Instant};
use async_trait::async_trait;
use futures::future::*;
use futures::stream::FuturesUnordered;
use futures::StreamExt;
use serde::{Deserialize, Serialize};
use tokio::select;
use tokio::sync::{mpsc, watch};
use crate::background::WorkerInfo;
use crate::error::Error;
use crate::time::now_msec;
#[derive(PartialEq, Copy, Clone, Serialize, Deserialize, Debug)]
pub enum WorkerState {
Busy,
Throttled(f32),
Idle,
Done,
}
impl std::fmt::Display for WorkerState {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
WorkerState::Busy => write!(f, "Busy"),
WorkerState::Throttled(t) => write!(f, "Thr:{:.3}", t),
WorkerState::Idle => write!(f, "Idle"),
WorkerState::Done => write!(f, "Done"),
}
}
}
#[async_trait]
pub trait Worker: Send {
fn name(&self) -> String;
fn info(&self) -> Option<String> {
None
}
/// Work: do a basic unit of work, if one is available (otherwise, should return
/// WorkerState::Idle immediately). We will do our best to not interrupt this future in the
/// middle of processing, it will only be interrupted at the last minute when Garage is trying
/// to exit and this hasn't returned yet. This function may return an error to indicate that
/// its unit of work could not be processed due to an error: the error will be logged and
/// .work() will be called again after a short delay.
async fn work(&mut self, must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error>;
/// Wait for work: await for some task to become available. This future can be interrupted in
/// the middle for any reason. This future doesn't have to await on must_exit.changed(), we
/// are doing it for you. Therefore it only receives a read refernce to must_exit which allows
/// it to check if we are exiting.
async fn wait_for_work(&mut self, must_exit: &watch::Receiver<bool>) -> WorkerState;
}
pub(crate) struct WorkerProcessor {
stop_signal: watch::Receiver<bool>,
worker_chan: mpsc::UnboundedReceiver<Box<dyn Worker>>,
worker_info: Arc<std::sync::Mutex<HashMap<usize, WorkerInfo>>>,
}
impl WorkerProcessor {
pub(crate) fn new(
worker_chan: mpsc::UnboundedReceiver<Box<dyn Worker>>,
stop_signal: watch::Receiver<bool>,
worker_info: Arc<std::sync::Mutex<HashMap<usize, WorkerInfo>>>,
) -> Self {
Self {
stop_signal,
worker_chan,
worker_info,
}
}
pub(crate) async fn run(&mut self) {
let mut workers = FuturesUnordered::new();
let mut next_task_id = 1;
while !*self.stop_signal.borrow() {
let await_next_worker = async {
if workers.is_empty() {
futures::future::pending().await
} else {
workers.next().await
}
};
select! {
new_worker_opt = self.worker_chan.recv() => {
if let Some(new_worker) = new_worker_opt {
let task_id = next_task_id;
next_task_id += 1;
let stop_signal = self.stop_signal.clone();
let stop_signal_worker = self.stop_signal.clone();
let mut worker = WorkerHandler {
task_id,
stop_signal,
stop_signal_worker,
worker: new_worker,
state: WorkerState::Busy,
errors: 0,
consecutive_errors: 0,
last_error: None,
};
workers.push(async move {
worker.step().await;
worker
}.boxed());
}
}
worker = await_next_worker => {
if let Some(mut worker) = worker {
trace!("{} (TID {}): {:?}", worker.worker.name(), worker.task_id, worker.state);
// Save worker info
let mut wi = self.worker_info.lock().unwrap();
match wi.get_mut(&worker.task_id) {
Some(i) => {
i.state = worker.state;
i.info = worker.worker.info();
i.errors = worker.errors;
i.consecutive_errors = worker.consecutive_errors;
if worker.last_error.is_some() {
i.last_error = worker.last_error.take();
}
}
None => {
wi.insert(worker.task_id, WorkerInfo {
name: worker.worker.name(),
state: worker.state,
info: worker.worker.info(),
errors: worker.errors,
consecutive_errors: worker.consecutive_errors,
last_error: worker.last_error.take(),
});
}
}
if worker.state == WorkerState::Done {
info!("Worker {} (TID {}) exited", worker.worker.name(), worker.task_id);
} else {
workers.push(async move {
worker.step().await;
worker
}.boxed());
}
}
}
_ = self.stop_signal.changed() => (),
}
}
// We are exiting, drain everything
let drain_half_time = Instant::now() + Duration::from_secs(5);
let drain_everything = async move {
while let Some(mut worker) = workers.next().await {
if worker.state == WorkerState::Done {
info!(
"Worker {} (TID {}) exited",
worker.worker.name(),
worker.task_id
);
} else if Instant::now() > drain_half_time {
warn!("Worker {} (TID {}) interrupted between two iterations in state {:?} (this should be fine)", worker.worker.name(), worker.task_id, worker.state);
} else {
workers.push(
async move {
worker.step().await;
worker
}
.boxed(),
);
}
}
};
select! {
_ = drain_everything => {
info!("All workers exited peacefully \\o/");
}
_ = tokio::time::sleep(Duration::from_secs(9)) => {
error!("Some workers could not exit in time, we are cancelling some things in the middle");
}
}
}
}
struct WorkerHandler {
task_id: usize,
stop_signal: watch::Receiver<bool>,
stop_signal_worker: watch::Receiver<bool>,
worker: Box<dyn Worker>,
state: WorkerState,
errors: usize,
consecutive_errors: usize,
last_error: Option<(String, u64)>,
}
impl WorkerHandler {
async fn step(&mut self) {
match self.state {
WorkerState::Busy => match self.worker.work(&mut self.stop_signal).await {
Ok(s) => {
self.state = s;
self.consecutive_errors = 0;
}
Err(e) => {
error!(
"Error in worker {} (TID {}): {}",
self.worker.name(),
self.task_id,
e
);
self.errors += 1;
self.consecutive_errors += 1;
self.last_error = Some((format!("{}", e), now_msec()));
// Sleep a bit so that error won't repeat immediately, exponential backoff
// strategy (min 1sec, max ~60sec)
self.state = WorkerState::Throttled(
(1.5f32).powf(std::cmp::min(10, self.consecutive_errors - 1) as f32),
);
}
},
WorkerState::Throttled(delay) => {
// Sleep for given delay and go back to busy state
if !*self.stop_signal.borrow() {
select! {
_ = tokio::time::sleep(Duration::from_secs_f32(delay)) => (),
_ = self.stop_signal.changed() => (),
}
}
self.state = WorkerState::Busy;
}
WorkerState::Idle => {
if *self.stop_signal.borrow() {
select! {
new_st = self.worker.wait_for_work(&self.stop_signal_worker) => {
self.state = new_st;
}
_ = tokio::time::sleep(Duration::from_secs(1)) => {
// stay in Idle state
}
}
} else {
select! {
new_st = self.worker.wait_for_work(&self.stop_signal_worker) => {
self.state = new_st;
}
_ = self.stop_signal.changed() => {
// stay in Idle state
}
}
}
}
WorkerState::Done => unreachable!(),
}
}
}
