1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
use core::future::Future;
use std::pin::Pin;
use std::sync::Arc;
use std::time::Duration;
use futures::future::*;
use futures::select;
use tokio::sync::{mpsc, watch, Mutex};
use crate::error::Error;
type JobOutput = Result<(), Error>;
type Job = Pin<Box<dyn Future<Output = JobOutput> + Send>>;
pub struct BackgroundRunner {
pub stop_signal: watch::Receiver<bool>,
queue_in: mpsc::UnboundedSender<(Job, bool)>,
worker_in: mpsc::UnboundedSender<tokio::task::JoinHandle<()>>,
}
impl BackgroundRunner {
pub fn new(
n_runners: usize,
stop_signal: watch::Receiver<bool>,
) -> (Arc<Self>, tokio::task::JoinHandle<()>) {
let (worker_in, mut worker_out) = mpsc::unbounded_channel();
let stop_signal_2 = stop_signal.clone();
let await_all_done = tokio::spawn(async move {
loop {
let wkr = {
select! {
item = worker_out.recv().fuse() => {
match item {
Some(x) => x,
None => break,
}
}
_ = tokio::time::sleep(Duration::from_secs(10)).fuse() => {
if *stop_signal_2.borrow() {
break;
} else {
continue;
}
}
}
};
if let Err(e) = wkr.await {
error!("Error while awaiting for worker: {}", e);
}
}
});
let (queue_in, queue_out) = mpsc::unbounded_channel();
let queue_out = Arc::new(Mutex::new(queue_out));
for i in 0..n_runners {
let queue_out = queue_out.clone();
let stop_signal = stop_signal.clone();
worker_in
.send(tokio::spawn(async move {
loop {
let (job, cancellable) = {
select! {
item = wait_job(&queue_out).fuse() => match item {
// We received a task, process it
Some(x) => x,
// We received a signal that no more tasks will ever be sent
// because the sending side was dropped. Exit now.
None => break,
},
_ = tokio::time::sleep(Duration::from_secs(10)).fuse() => {
if *stop_signal.borrow() {
// Nothing has been going on for 10 secs, and we are shutting
// down. Exit now.
break;
} else {
// Nothing is going on but we don't want to exit.
continue;
}
}
}
};
if cancellable && *stop_signal.borrow() {
continue;
}
if let Err(e) = job.await {
error!("Job failed: {}", e)
}
}
info!("Background worker {} exiting", i);
}))
.unwrap();
}
let bgrunner = Arc::new(Self {
stop_signal,
queue_in,
worker_in,
});
(bgrunner, await_all_done)
}
// Spawn a task to be run in background
pub fn spawn<T>(&self, job: T)
where
T: Future<Output = JobOutput> + Send + 'static,
{
let boxed: Job = Box::pin(job);
self.queue_in
.send((boxed, false))
.map_err(|_| "could not put job in queue")
.unwrap();
}
pub fn spawn_cancellable<T>(&self, job: T)
where
T: Future<Output = JobOutput> + Send + 'static,
{
let boxed: Job = Box::pin(job);
self.queue_in
.send((boxed, true))
.map_err(|_| "could not put job in queue")
.unwrap();
}
pub fn spawn_worker<F, T>(&self, name: String, worker: F)
where
F: FnOnce(watch::Receiver<bool>) -> T + Send + 'static,
T: Future<Output = ()> + Send + 'static,
{
let stop_signal = self.stop_signal.clone();
let task = tokio::spawn(async move {
info!("Worker started: {}", name);
worker(stop_signal).await;
info!("Worker exited: {}", name);
});
self.worker_in
.send(task)
.map_err(|_| "could not put job in queue")
.unwrap();
}
}
async fn wait_job(q: &Mutex<mpsc::UnboundedReceiver<(Job, bool)>>) -> Option<(Job, bool)> {
q.lock().await.recv().await
}
|
