From 5eee9e62e5296087e32825b0156fc911ee040c79 Mon Sep 17 00:00:00 2001
From: Jack May <jack@solana.com>
Date: Wed, 1 May 2019 14:29:57 -0700
Subject: [PATCH] Add swapper back-off (#4088)

* Add swapper back-off

* Reset back-off if bench-exchange suspects back-log

* nudge

* nudge
---
 bench-exchange/src/bench.rs | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/bench-exchange/src/bench.rs b/bench-exchange/src/bench.rs
index 332134f4c4..4797b839a1 100644
--- a/bench-exchange/src/bench.rs
+++ b/bench-exchange/src/bench.rs
@@ -181,6 +181,7 @@ where
                     &shared_txs,
                     &swapper_signers,
                     &profit_pubkeys,
+                    transfer_delay,
                     batch_size,
                     chunk_size,
                     account_groups,
@@ -358,6 +359,7 @@ fn swapper<T>(
     shared_txs: &SharedTransactions,
     signers: &[Arc<Keypair>],
     profit_pubkeys: &[Pubkey],
+    transfer_delay: u64,
     batch_size: usize,
     chunk_size: usize,
     account_groups: usize,
@@ -373,6 +375,18 @@ fn swapper<T>(
     let mut now = Instant::now();
     let start_time = now;
     let mut total_elapsed = start_time.elapsed();
+
+    // Chunks may have been dropped and we don't want to wait a long time
+    // for each time, Back-off each time we fail to confirm a chunk
+    const CHECK_TX_TIMEOUT_MAX_MS: u64 = 15000;
+    const CHECK_TX_DELAY_MS: u64 = 100;
+    let mut max_tries = CHECK_TX_TIMEOUT_MAX_MS / CHECK_TX_DELAY_MS;
+
+    // If we dump too many chunks maybe we are just waiting on a back-log
+    // rather than a series of dropped packets, reset to max waits
+    const MAX_DUMPS: u64 = 50;
+    let mut dumps = 0;
+
     'outer: loop {
         if let Ok(trade_infos) = receiver.try_recv() {
             let mut tries = 0;
@@ -383,17 +397,27 @@ fn swapper<T>(
                 == 0
             {
                 tries += 1;
-                if tries > 300 {
+                if tries >= max_tries {
                     if exit_signal.load(Ordering::Relaxed) {
                         break 'outer;
                     }
-                    error!("Give up waiting, dump batch");
+                    error!("Give up and dump batch");
+                    if dumps >= MAX_DUMPS {
+                        error!("Max batches dumped, reset wait back-off");
+                        max_tries = CHECK_TX_TIMEOUT_MAX_MS / CHECK_TX_DELAY_MS;
+                        dumps = 0;
+                    } else {
+                        dumps += 1;
+                        max_tries /= 2;
+                    }
                     continue 'outer;
                 }
                 debug!("{} waiting for trades batch to clear", tries);
-                sleep(Duration::from_millis(100));
+                sleep(Duration::from_millis(CHECK_TX_DELAY_MS));
                 trade_index = thread_rng().gen_range(0, trade_infos.len());
             }
+            max_tries = CHECK_TX_TIMEOUT_MAX_MS / CHECK_TX_DELAY_MS;
+            dumps = 0;
 
             trade_infos.iter().for_each(|info| {
                 order_book
@@ -473,6 +497,8 @@ fn swapper<T>(
                     shared_txs_wl.push_back(chunk.to_vec());
                 }
             }
+            // Throttle the swapper so it doesn't try to catchup unbridled
+            sleep(Duration::from_millis(transfer_delay / 2));
         }
 
         if exit_signal.load(Ordering::Relaxed) {
@@ -986,9 +1012,9 @@ mod tests {
 
         let mut config = Config::default();
         config.identity = Keypair::new();
-        config.threads = 1;
         config.duration = Duration::from_secs(1);
         config.fund_amount = 100_000;
+        config.threads = 1;
         config.transfer_delay = 20; // 15
         config.batch_size = 100; // 1000;
         config.chunk_size = 10; // 200;
@@ -1058,9 +1084,9 @@ mod tests {
 
         let mut config = Config::default();
         config.identity = identity;
-        config.threads = 1;
         config.duration = Duration::from_secs(1);
         config.fund_amount = 100_000;
+        config.threads = 1;
         config.transfer_delay = 20; // 0;
         config.batch_size = 100; // 1500;
         config.chunk_size = 10; // 1500;