From 40aa4ba7674f43ef4b677104096610dd9bdd9091 Mon Sep 17 00:00:00 2001
From: Robert Coltheart <robert.coltheart@gmail.com>
Date: Thu, 11 Apr 2024 08:07:41 +1000
Subject: [PATCH] fix: prevent hanging if stop called from multiple threads

---
 src/KafkaFlow/KafkaBus.cs | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/KafkaFlow/KafkaBus.cs b/src/KafkaFlow/KafkaBus.cs
index 246fd5f41..205f26386 100644
--- a/src/KafkaFlow/KafkaBus.cs
+++ b/src/KafkaFlow/KafkaBus.cs
@@ -18,6 +18,8 @@ internal class KafkaBus : IKafkaBus
 
     private readonly List<IConsumerManager> _consumerManagers = new();
 
+    private bool _stopped;
+
     public KafkaBus(
         IDependencyResolver dependencyResolver,
         KafkaConfiguration configuration,
@@ -73,12 +75,22 @@ public async Task StartAsync(CancellationToken stopCancellationToken = default)
 
     public Task StopAsync()
     {
-        foreach (var cluster in _configuration.Clusters)
+        lock (_consumerManagers)
         {
-            cluster.OnStoppingHandler(_dependencyResolver);
-        }
+            if (_stopped)
+            {
+                return Task.CompletedTask;
+            }
 
-        return Task.WhenAll(_consumerManagers.Select(x => x.StopAsync()));
+            _stopped = true;
+
+            foreach (var cluster in _configuration.Clusters)
+            {
+                cluster.OnStoppingHandler(_dependencyResolver);
+            }
+
+            return Task.WhenAll(_consumerManagers.Select(x => x.StopAsync()));
+        }
     }
 
     private async Task CreateMissingClusterTopics(ClusterConfiguration cluster)