From 92b0eaec65459e9306a3e7d15876f79460d2dab6 Mon Sep 17 00:00:00 2001
From: Bryce Anderson <bryce_anderson@apple.com>
Date: Wed, 18 Oct 2023 09:58:19 -0700
Subject: [PATCH] Fix the flaky LingeringRoundRobinLoadBalancerTest

Motivation:

The test `expiringAHostDoesntRaceWithConnectionAdding` is flaky
but only in CI. This is because locally we never hit the `else`
branch where the connection was added first but it does happen
in CI. That branch of the test is flawed: the host is marked
as EXPIRED and thus unhealthy, so we should always expect a
NoActiveHostException instead of a NoAvailableHostException.

Note that this branch can be tested by wating for the future `f`
to complete before sending the service discovery event.

Modifications:

Change the expected exception to NoActiveHostException.

Result:

Test shouldn't be flaky anymore.
---
 .../loadbalancer/LingeringRoundRobinLoadBalancerTest.java   | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/LingeringRoundRobinLoadBalancerTest.java b/servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/LingeringRoundRobinLoadBalancerTest.java
index ce06d7a6ea..a83f809406 100644
--- a/servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/LingeringRoundRobinLoadBalancerTest.java
+++ b/servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/LingeringRoundRobinLoadBalancerTest.java
@@ -135,6 +135,7 @@ void expiringAHostDoesntRaceWithConnectionAdding() throws Exception {
                 return null;
             }).toFuture();
 
+            // Note that this will send a `EXPIRED` event and the host will remain, but be marked unhealthy.
             sendServiceDiscoveryEvents(downEvent("address-1"));
             f.get();
 
@@ -157,7 +158,10 @@ void expiringAHostDoesntRaceWithConnectionAdding() throws Exception {
                 // Confirm host is expired:
                 ExecutionException ex = assertThrows(ExecutionException.class,
                         () -> lb.selectConnection(alwaysNewConnectionFilter(), null).toFuture().get());
-                assertThat(ex.getCause(), instanceOf(NoAvailableHostException.class));
+
+                // We expect a `NoActiveHostException` because the host exists, but was marked
+                // as unhealthy because it is expired.
+                assertThat(ex.getCause(), instanceOf(NoActiveHostException.class));
 
                 lb.closeAsyncGracefully().toFuture().get();
                 verify(connection.get(), times(1)).closeAsyncGracefully();