Add support for concurrent downloads to client_benchmark example

Signed-off-by: Alessandro Passaro <alexpax@amazon.co.uk>

mountpoint-s3-client/examples/client_benchmark.rs

@@ -1,6 +1,7 @@
 use std::pin::pin;
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
+use std::thread;
 use std::time::Instant;
 
 use clap::{Parser, Subcommand};
@@ -27,29 +28,42 @@ fn init_tracing_subscriber() {
     subscriber.try_init().expect("unable to install global subscriber");
 }
 
-fn run_benchmark(client: impl ObjectClient + Clone, num_iterations: usize, bucket: &str, key: &str) {
+fn run_benchmark(
+    client: impl ObjectClient + Clone + Send,
+    num_iterations: usize,
+    num_downloads: usize,
+    bucket: &str,
+    key: &str,
+) {
     for i in 0..num_iterations {
-        let received_size = Arc::new(AtomicU64::new(0));
-        let client = client.clone();
-        let received_size_clone = Arc::clone(&received_size);
         let start = Instant::now();
-        futures::executor::block_on(async move {
-            let mut request = client
-                .get_object(bucket, key, None, None)
-                .await
-                .expect("couldn't create get request");
-            let mut request = pin!(request);
-            loop {
-                match StreamExt::next(&mut request).await {
-                    Some(Ok((_offset, body))) => {
-                        received_size_clone.fetch_add(body.len() as u64, Ordering::SeqCst);
-                    }
-                    Some(Err(e)) => {
-                        tracing::error!(error = ?e, "request failed");
-                        break;
-                    }
-                    None => break,
-                }
+        let received_size = Arc::new(AtomicU64::new(0));
+
+        thread::scope(|scope| {
+            for _ in 0..num_downloads {
+                let client = client.clone();
+                let received_size_clone = Arc::clone(&received_size);
+                scope.spawn(|| {
+                    futures::executor::block_on(async move {
+                        let mut request = client
+                            .get_object(bucket, key, None, None)
+                            .await
+                            .expect("couldn't create get request");
+                        let mut request = pin!(request);
+                        loop {
+                            match request.next().await {
+                                Some(Ok((_offset, body))) => {
+                                    received_size_clone.fetch_add(body.len() as u64, Ordering::SeqCst);
+                                }
+                                Some(Err(e)) => {
+                                    tracing::error!(error = ?e, "request failed");
+                                    break;
+                                }
+                                None => break,
+                            }
+                        }
+                    })
+                });
             }
         });
 
@@ -93,6 +107,8 @@ struct CliArgs {
     part_size: usize,
     #[arg(long, help = "Number of benchmark iterations", default_value = "1")]
     iterations: usize,
+    #[arg(long, help = "Number of concurrent downloads", default_value = "1")]
+    downloads: usize,
 }
 
 fn main() {
@@ -107,7 +123,7 @@ fn main() {
             config = config.part_size(args.part_size);
             let client = S3CrtClient::new(config).expect("couldn't create client");
 
-            run_benchmark(client, args.iterations, &bucket, &key);
+            run_benchmark(client, args.iterations, args.downloads, &bucket, &key);
         }
         Client::Mock { object_size } => {
             const BUCKET: &str = "bucket";
@@ -124,7 +140,7 @@ fn main() {
 
             client.add_object(KEY, MockObject::ramp(0xaa, object_size as usize, ETag::for_tests()));
 
-            run_benchmark(client, args.iterations, BUCKET, "key");
+            run_benchmark(client, args.iterations, args.downloads, BUCKET, KEY);
         }
     }
 }