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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
use std::{
panic,
sync::{
atomic::{ AtomicBool, Ordering },
mpsc::{ self, RecvTimeoutError },
Arc,
Mutex,
RwLock,
},
thread,
time::Duration,
};
// JOB/Function that we will run through threads
type Job = Box<dyn FnOnce() + Send + 'static>;
pub struct WorkerPool {
workers: Arc<RwLock<Vec<Worker>>>,
sender: Option<mpsc::Sender<Job>>,
shutdown_master: Arc<AtomicBool>,
}
impl WorkerPool {
/**
* Create workerpool with specific size
*/
pub fn new(size: usize) -> WorkerPool {
// Size must be greater than 0
assert!(size > 0);
// Initialize thread channle
let (sender, receiver) = mpsc::channel();
// Wrap receiver with Atomic refercounter
let receiver = Arc::new(Mutex::new(receiver));
let workers = Arc::new(RwLock::new(Vec::with_capacity(size)));
// Block scope initialize all workers
{
let binding = Arc::clone(&workers);
let mut write_worker = binding.write().unwrap();
for id in 0..size {
write_worker.push(Worker::new(id, Arc::clone(&receiver)));
}
}
// AtomicBool for drop master thread
let shutdown_flag = Arc::new(AtomicBool::new(false));
// Clone for move it into thread
let shutdown_clone = Arc::clone(&shutdown_flag);
let worker_clone = Arc::clone(&workers);
let receiver_clone = Arc::clone(&receiver);
// Run master thread
thread::spawn(move || {
loop {
// Catch if master thread panics
let result = panic::catch_unwind({
let shutdown_flag = Arc::clone(&shutdown_clone);
let worker_clone = Arc::clone(&worker_clone);
let receiver_clone = Arc::clone(&receiver_clone);
move || {
// While workerpool in scope
while !shutdown_flag.load(Ordering::Relaxed) {
// Check dead worker every 4s
thread::sleep(Duration::from_secs(4));
// Find all dead workers
let dead_worker_id: Vec<usize> = {
// Safely gets read lock
let workers = match worker_clone.read() {
Ok(w) => w,
Err(e) => {
eprintln!("Watchdog lock poisoned: {e}");
continue;
}
};
// Filter out all dead workers
workers
.iter()
.filter(|w| {
w.thread
.as_ref()
.map(|t| t.is_finished())
.unwrap_or(true)
})
.map(|w| w.id)
.collect()
};
// Replace with new workers
for id in dead_worker_id {
let new_worker = Worker::new(id, Arc::clone(&receiver_clone));
if let Ok(mut workers) = worker_clone.write() {
if let Some(slot) = workers.iter_mut().find(|w| w.id == id) {
*slot = new_worker;
}
} else {
eprintln!("Can't get worker write lock");
}
}
}
}
});
// Panic master thread restart it
if result.is_err() {
eprintln!("Master thread panicked. Restarting master thread");
thread::sleep(Duration::from_secs(1));
continue;
} else {
// Case workepool drop
break;
}
}
});
WorkerPool {
workers,
sender: Some(sender),
shutdown_master: shutdown_flag,
}
}
// Execute jobs
pub fn execute<F>(&self, f: F) where F: FnOnce() + Send + 'static {
let job = Box::new(f);
if let Some(sender) = &self.sender {
if sender.send(job).is_err() {
eprintln!("Failed to send job: worker pool might be shutting down.");
}
}
}
}
// Implement drop
impl Drop for WorkerPool {
fn drop(&mut self) {
self.shutdown_master.store(true, Ordering::Relaxed);
drop(self.sender.take());
let mut workers = self.workers.write().unwrap();
for worker in workers.iter_mut() {
println!("Shutting down worker {}", worker.id);
if let Some(thread) = worker.thread.take() {
thread.join().unwrap();
}
}
}
}
struct Worker {
id: usize,
thread: Option<thread::JoinHandle<()>>,
}
impl Worker {
// Create new worker
fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
let thread = thread::spawn(move || {
loop {
let message = receiver.lock().unwrap().recv_timeout(Duration::from_secs(1));
match message {
Ok(job) => {
let result = panic::catch_unwind(panic::AssertUnwindSafe(job));
if result.is_err() {
eprintln!("Worker {id} panicked while executing a job.");
}
}
Err(RecvTimeoutError::Timeout) => {
thread::yield_now();
}
Err(_) => {
eprintln!("Worker {id} disconnected; shutting down.");
break;
}
}
}
});
Worker {
id,
thread: Some(thread),
}
}
}