Add stress test (#3222)

Created a simple echo TCP server that on two different runtimes that is
called from a GitHub action using Valgrind to ensure that there are
no memory leaks.

Fixes: #3022

stress-test/examples/simple_echo_tcp.rs

@@ -0,0 +1,58 @@
+//! Simple TCP echo server to check memory leaks using Valgrind.
+use std::{thread::sleep, time::Duration};
+
+use tokio::{
+    io::{AsyncReadExt, AsyncWriteExt},
+    net::{TcpListener, TcpSocket},
+    runtime::Builder,
+    sync::oneshot,
+};
+
+const TCP_ENDPOINT: &str = "127.0.0.1:8080";
+const NUM_MSGS: usize = 10_000;
+const MSG_SIZE: usize = 1024;
+
+fn main() {
+    let rt = Builder::new_multi_thread().enable_io().build().unwrap();
+    let rt2 = Builder::new_multi_thread().enable_io().build().unwrap();
+
+    rt.spawn(async {
+        let listener = TcpListener::bind(TCP_ENDPOINT).await.unwrap();
+        let (mut socket, _) = listener.accept().await.unwrap();
+        let (mut rd, mut wr) = socket.split();
+        while tokio::io::copy(&mut rd, &mut wr).await.is_ok() {}
+    });
+
+    // wait a bit so that the listener binds.
+    sleep(Duration::from_millis(100));
+
+    // create a channel to let the main thread know that all the messages were sent and received.
+    let (tx, mut rx) = oneshot::channel();
+
+    rt2.spawn(async {
+        let addr = TCP_ENDPOINT.parse().unwrap();
+        let socket = TcpSocket::new_v4().unwrap();
+        let mut stream = socket.connect(addr).await.unwrap();
+
+        let mut buff = [0; MSG_SIZE];
+        for _ in 0..NUM_MSGS {
+            let one_mega_random_bytes: Vec<u8> =
+                (0..MSG_SIZE).map(|_| rand::random::<u8>()).collect();
+            stream
+                .write_all(one_mega_random_bytes.as_slice())
+                .await
+                .unwrap();
+            stream.read(&mut buff).await.unwrap();
+        }
+        tx.send(()).unwrap();
+    });
+
+    loop {
+        // check that we're done.
+        match rx.try_recv() {
+            Err(oneshot::error::TryRecvError::Empty) => (),
+            Err(oneshot::error::TryRecvError::Closed) => panic!("channel got closed..."),
+            Ok(()) => break,
+        }
+    }
+}