Drain a Vec<_> from within a tokio task - rust

Question

I have a buffer of type Vec<i32> which I want to write to disk and .drain() it after a certain time. The problem I'm facing is that of ownership. How can I write the contents of the buffer to disk and .drain() it without taking ownership or is it not possible in this case because of the tokio tasks?
use tokio::sync::mpsc;
use std::time::Duration;
use std::fs::File;
use std::io::BufWriter;
use serde_json;
#[tokio::main]
async fn main() {
let mut buffer: Vec<i32> = Vec::new();
let mut interval = tokio::time::interval(Duration::from_secs(60));
let (tx, mut rx) = mpsc::unbounded_channel();
let sender_handle = tokio::spawn(async move {
for i in 0..5 {
tx.send(i).unwrap();
}
});
let receiver_handle = tokio::spawn(async move {
while let Some(x) = rx.recv().await {
buffer.push(x);
}
});
let interval_handle = tokio::spawn(async move {
loop {
interval.tick().await;
let file: File::create("buffer.txt");
let mut writer = BufWriter::new(file.unwrap());
serde_json::to_writer(&mut writer, &buffer);
buffer.drain(..);
}
});
let (_, _, _) = tokio::join!(sender_handle, receiver_handle, interval_handle);
}

Answer 1

You need to add some sync mechanism so the access to the vector is controlled. An Arc<Mutex<Vec<_>>> would do:
use futures::lock::Mutex;
use std::sync::Arc;
use tokio::sync::mpsc;
use std::time::Duration;
use std::fs::File;
use std::io::BufWriter;
use serde_json;
#[tokio::main]
async fn main() {
let buffer: Arc<Mutex<Vec<i32>>> = Arc::new(Mutex::new(Vec::new()));
let mut interval = tokio::time::interval(Duration::from_secs(60));
let (tx, mut rx) = mpsc::unbounded_channel();
let sender_handle = tokio::spawn(async move {
for i in 0..5 {
tx.send(i).unwrap();
}
});
let receiver_buff = buffer.clone();
let receiver_handle = tokio::spawn(async move {
while let Some(x) = rx.recv().await {
let mut buff = receiver_buff.lock().await;
buff.push(x);
}
});
let interval_handle = tokio::spawn(async move {
let buffer = buffer.clone();
loop {
interval.tick().await;
let file = File::create("buffer.txt");
let mut writer = BufWriter::new(file.unwrap());
let mut buff = buffer.lock().await;
serde_json::to_writer(&mut writer, &*buff).expect("Serialization to go well");
buff.drain(..);
}
});
let (_, _, _) = tokio::join!(sender_handle, receiver_handle, interval_handle);
}
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