feat(udp-kafka-bridge): check backpressure (#20194)

hm-kafka/kafka-client/kafka-rust/udp-kafka-bridge/src/main.rs

@@ -30,7 +30,9 @@ struct ProcessingContext {
 fn create_producer(bootstrap_server: &str) -> FutureProducer {
     ClientConfig::new()
         .set("bootstrap.servers", bootstrap_server)
-        .set("batch.size", "20971520") // 20 MiB
+        .set("batch.size", "1048576") // 1 MiB
+        .set("queue.buffering.max.messages", "100000") // Limit in-flight messages
+        .set("queue.buffering.max.kbytes", "1048576") // 1GB max memory usage
         .set("linger.ms", "2")
         .set("compression.type", "zstd")
         .create()
@@ -43,7 +45,6 @@ async fn process_message(
 ) -> Result<(), Box<dyn Error + Send + Sync>> {
     let mut buf = Vec::new();
     motor.encode(&mut buf)?;
-
     let proto_payload = context
         .encoder
         .encode(
@@ -58,6 +59,7 @@ async fn process_message(
         .id
         .clone()
         .unwrap_or_else(|| "unknown_motor".to_string());
+
     context
         .producer
         .send(
@@ -70,7 +72,7 @@ async fn process_message(
         .map_err(|(err, _)| Box::new(err) as Box<dyn Error + Send + Sync>)?;
 
     let count = context.message_count.fetch_add(1, Ordering::Relaxed) + 1;
-    if count % 100000 == 0 {
+    if count % 100_000 == 0 {
         let duration = context.start_time.elapsed();
         println!(
             "Total messages sent to Kafka: {}, Time elapsed: {:?}, Avg msg/sec: {:.2}",
@@ -87,10 +89,19 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let start_time = Instant::now();
     println!("Starting UDP listener and Kafka producer...");
 
+    const CHANNEL_BUFFER_SIZE: usize = 10_000_000;
+    const LOW_CAPACITY_THRESHOLD: usize = CHANNEL_BUFFER_SIZE / 10; // 10% of buffer size
+
     // Set up UDP socket
     let socket = Socket::new(Domain::IPV4, Type::DGRAM, None)?;
     socket.set_reuse_address(true)?;
-    socket.set_recv_buffer_size(20 * 1024 * 1024)?;
+
+    // Set and get receive buffer size
+    let desired_recv_buf_size = 20 * 1024 * 1024; // 20MB
+    socket.set_recv_buffer_size(desired_recv_buf_size)?;
+    let actual_recv_buf_size = socket.recv_buffer_size()?;
+    println!("UDP receive buffer size: {} bytes", actual_recv_buf_size);
+
     let addr: SocketAddr = "127.0.0.1:50537".parse()?;
     socket.bind(&addr.into())?;
     let socket = UdpSocket::from_std(socket.into())?;
@@ -114,7 +125,11 @@ async fn main() -> Result<(), Box<dyn Error>> {
     });
 
     // Create channel for message processing
-    let (tx, mut rx) = mpsc::channel::<Motor>(1000000); // Buffer size of 1000000 messages
+    let (tx, mut rx) = mpsc::channel::<Motor>(CHANNEL_BUFFER_SIZE);
+    println!(
+        "Channel buffer size: {}, Low capacity threshold: {}",
+        CHANNEL_BUFFER_SIZE, LOW_CAPACITY_THRESHOLD
+    );
 
     // Spawn message processing task
     let processing_context = context.clone();
@@ -136,8 +151,27 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Main UDP receiving loop
     let mut buffer = vec![0u8; 65536];
+    let mut packet_count = 0;
     loop {
         let (amt, _src) = socket.recv_from(&mut buffer).await?;
+
+        // Monitor packet count and channel capacity
+        packet_count += 1;
+        if packet_count % 100_000 == 0 {
+            let current_capacity = tx.capacity();
+            println!(
+                "Processed {} packets, channel capacity: {} ({:.1}%)",
+                packet_count,
+                current_capacity,
+                (current_capacity as f64 / CHANNEL_BUFFER_SIZE as f64) * 100.0
+            );
+
+            // If channel capacity is low, this might indicate backpressure
+            if current_capacity < LOW_CAPACITY_THRESHOLD {
+                println!("Warning: Channel capacity running low - possible backpressure");
+            }
+        }
+
         match Motor::decode(&buffer[..amt]) {
             Ok(motor) => {
                 if let Err(e) = tx.send(motor).await {