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Rust tokio Semaphore example
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| use std::sync::Arc; | |
| use tokio::sync::{Semaphore, SemaphorePermit}; | |
| use tokio::time::sleep; | |
| use tokio::time::Duration; | |
| async fn person(sem: Arc<Semaphore>, name: String) { | |
| println!("Person {}: waiting for a permit", name); | |
| teller(sem, &name).await; | |
| println!("\tPerson {} finished", name); | |
| } | |
| async fn teller(sem: Arc<Semaphore>, name: &String) { | |
| // simulating time to walk to teller | |
| let time = rand::random::<u8>() % 3 + 1; | |
| sleep(Duration::from_secs(time as u64)).await; | |
| let permit: SemaphorePermit = sem.acquire().await.unwrap(); | |
| println!("Teller: I have a permit! for {}", name); | |
| // simulating time to talk to teller | |
| let time = rand::random::<u8>() % 3 + 2; | |
| println!(" Teller: Talking to {} for {} seconds", name, time); | |
| sleep(Duration::from_secs(time as u64)).await; | |
| drop(permit) | |
| } | |
| #[tokio::main] | |
| async fn main() { | |
| let num_tellers = 4; | |
| let sem = Semaphore::new(num_tellers); | |
| let sem_arc = Arc::new(sem); | |
| let mut handles = Vec::new(); | |
| for i in 0..10 { | |
| let name = format!("Person {}", i); | |
| handles.push(tokio::spawn(person(sem_arc.clone(), name))); | |
| } | |
| for handle in handles { | |
| handle.await.unwrap(); | |
| } | |
| } |
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Output
Person Person 0: waiting for a permit
Person Person 1: waiting for a permit
Person Person 2: waiting for a permit
Person Person 3: waiting for a permit
Person Person 4: waiting for a permit
Person Person 5: waiting for a permit
Person Person 6: waiting for a permit
Person Person 7: waiting for a permit
Person Person 8: waiting for a permit
Person Person 9: waiting for a permit
Teller: I have a permit! for Person 6
Teller: I have a permit! for Person 1
Teller: Talking to Person 1 for 4 seconds
Teller: Talking to Person 6 for 4 seconds
Teller: I have a permit! for Person 9
Teller: Talking to Person 9 for 4 seconds
Teller: I have a permit! for Person 5
Teller: Talking to Person 5 for 2 seconds
Person Person 5 finished
Teller: I have a permit! for Person 8
Teller: Talking to Person 8 for 4 seconds
Person Person 6 finished
Person Person 1 finished
Teller: I have a permit! for Person 7
Teller: Talking to Person 7 for 3 seconds
Teller: I have a permit! for Person 3
Teller: Talking to Person 3 for 3 seconds
Person Person 9 finished
Teller: I have a permit! for Person 4
Teller: Talking to Person 4 for 4 seconds
Person Person 8 finished
Person Person 7 finished
Person Person 3 finished
Teller: I have a permit! for Person 2
Teller: Talking to Person 2 for 3 seconds
Teller: I have a permit! for Person 0
Teller: Talking to Person 0 for 2 seconds
Person Person 4 finished
Person Person 0 finished
Person Person 2 finished