From bfb3de7a8a9c612774dd82d27f947f2c2dbdeaab Mon Sep 17 00:00:00 2001
From: Alfredo Garcia <oxarbitrage@gmail.com>
Date: Thu, 4 Feb 2021 23:42:38 -0300
Subject: [PATCH] Use use max_items as bound in tower-batch (#1691)

---
 tower-batch/src/service.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tower-batch/src/service.rs b/tower-batch/src/service.rs
index 7015af3c6..9598bd3c3 100644
--- a/tower-batch/src/service.rs
+++ b/tower-batch/src/service.rs
@@ -57,8 +57,12 @@ where
         T::Error: Send + Sync,
         Request: Send + 'static,
     {
-        // XXX(hdevalence): is this bound good
-        let bound = 1;
+        // The semaphore bound limits the maximum number of concurrent requests
+        // (specifically, requests which got a `Ready` from `poll_ready`, but haven't
+        // used their semaphore reservation in a `call` yet).
+        // We choose a bound that allows callers to check readiness for every item in
+        // a batch, then actually submit those items.
+        let bound = max_items;
         let (tx, rx) = mpsc::unbounded_channel();
         let (handle, worker) = Worker::new(service, rx, max_items, max_latency);
         tokio::spawn(worker.run());