exponentail backoff for retransmit

src/streamer.rs

@@ -159,11 +159,23 @@ fn find_next_missing(
 fn repair_window(
     locked_window: &Arc<RwLock<Vec<Option<SharedBlob>>>>,
     crdt: &Arc<RwLock<Crdt>>,
+    last: &mut usize,
+    times: &mut usize,
     consumed: &mut usize,
     received: &mut usize,
 ) -> Result<()> {
     let reqs = find_next_missing(locked_window, crdt, consumed, received)?;
-    info!("repair_window {} {}", *consumed, *received);
+    //exponential backoff
+    if *last != *consumed {
+        *times = 0;
+    }
+    *last = *consumed;
+    *times += 1;
+    //if times flips from all 1s 7 -> 8, 15 -> 16, we retry otherwise return Ok
+    if *times & (*times - 1) != 0 {
+        return Ok(());
+    }
+    info!("repair_window request {} {}", *consumed, *received);
     let sock = UdpSocket::bind("0.0.0.0:0")?;
     for (to, req) in reqs {
         //todo cache socket
@@ -307,6 +319,8 @@ pub fn window(
     spawn(move || {
         let mut consumed = 0;
         let mut received = 0;
+        let mut last = 0;
+        let mut times = 0;
         loop {
             if exit.load(Ordering::Relaxed) {
                 break;
@@ -321,7 +335,14 @@ pub fn window(
                 &s,
                 &retransmit,
             );
-            let _ = repair_window(&window, &crdt, &mut consumed, &mut received);
+            let _ = repair_window(
+                &window,
+                &crdt,
+                &mut last,
+                &mut times,
+                &mut consumed,
+                &mut received,
+            );
         }
     })
 }