From a4a412ef5da72e943a04322e05de484ebb7f035a Mon Sep 17 00:00:00 2001
From: Spencer Ferris <3319370+spencewenski@users.noreply.github.com>
Date: Wed, 24 Apr 2024 22:16:08 -0700
Subject: [PATCH] Add a yield to prevent `Processor` from hogging redis
 connections

Problem
-------
When there are no sidekiq jobs available in redis, there are no `await`s
between when `brpop`returns and when the next connection is acquired
from the pool. This means tokio's task scheduler doesn't have a chance
to switch to another task that's waiting for a connection.

Solution
--------
Add a `tokio::task::yield_now().await` in the case where there is no
actual job to handle. This allows tokio's task scheduler to wake up a
different task that's waiting for a connection.

https://github.com/film42/sidekiq-rs/issues/43
---
 src/processor.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/processor.rs b/src/processor.rs
index 2d183d5..0d5f450 100644
--- a/src/processor.rs
+++ b/src/processor.rs
@@ -122,6 +122,11 @@ impl Processor {
         let work = self.fetch().await?;
 
         if work.is_none() {
+            // If there is no job to handle, we need to add a `yield_now` in order to allow tokio's
+            // scheduler to wake up another task that may be waiting to acquire a connection from
+            // the Redis connection pool. See the following issue for more details:
+            // https://github.com/film42/sidekiq-rs/issues/43
+            tokio::task::yield_now().await;
             return Ok(WorkFetcher::NoWorkFound);
         }
         let mut work = work.expect("polled and found some work");