Enable Halibut TCP Keepalives by default! Again!! (#717)

This reverts commit b1bf60a, which results in Tcp KeepAlives being enabled by default.

source/Octopus.Tentacle.Tests/Communications/TentacleCommunicationsModuleFixture.cs

@@ -0,0 +1,91 @@
+using System;
+using Autofac;
+using FluentAssertions;
+using Halibut;
+using NUnit.Framework;
+using Octopus.Tentacle.Communications;
+using Octopus.Tentacle.Configuration;
+using Octopus.Tentacle.Tests.Commands;
+using Octopus.Tentacle.Variables;
+
+namespace Octopus.Tentacle.Tests.Communications
+{
+    public class TentacleCommunicationsModuleFixture
+    {
+        [Test]
+        [NonParallelizable]
+        public void HalibutTcpKeepAlivesShouldBeEnabledByDefault()
+        {
+            var container = BuildContainer();
+
+            var halibutRuntime = container.Resolve<HalibutRuntime>();
+
+            halibutRuntime.TimeoutsAndLimits.TcpKeepAliveEnabled.Should().BeTrue();
+        }
+
+        [Test]
+        [NonParallelizable]
+        public void HalibutTcpKeepAlivesCanBeDisabledWithAnEnvironmentVariable()
+        {
+            try
+            {
+                Environment.SetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled, "False");
+
+                var container = BuildContainer();
+
+                var halibutRuntime = container.Resolve<HalibutRuntime>();
+
+                halibutRuntime.TimeoutsAndLimits.TcpKeepAliveEnabled.Should().BeFalse();
+            }
+            finally
+            {
+                Environment.SetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled, "");
+            }
+        } 
+
+        [Test]
+        [NonParallelizable]
+        public void AnEmptyHalibutTcpKeepAlivesEnvironmentVariableIsIgnored()
+        {
+            Environment.SetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled, "");
+
+            var container = BuildContainer();
+
+            var halibutRuntime = container.Resolve<HalibutRuntime>();
+
+            halibutRuntime.TimeoutsAndLimits.TcpKeepAliveEnabled.Should().BeTrue();
+        } 
+
+        [Test]
+        [NonParallelizable]
+        public void AnInvalidHalibutTcpKeepAlivesEnvironmentVariableIsIgnored()
+        {
+            try
+            {
+                Environment.SetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled, "NOTABOOL");
+
+                var container = BuildContainer();
+
+                var halibutRuntime = container.Resolve<HalibutRuntime>();
+
+                halibutRuntime.TimeoutsAndLimits.TcpKeepAliveEnabled.Should().BeTrue();
+            }
+            finally
+            {
+                Environment.SetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled, "");
+            }
+        } 
+
+        static IContainer BuildContainer()
+        {
+            var builder = new ContainerBuilder();
+            var configuration = new StubTentacleConfiguration();
+            configuration.TentacleCertificate = configuration.GenerateNewCertificate();
+            configuration.AddOrUpdateTrustedOctopusServer(new OctopusServerConfiguration("NOPE"));
+            builder.RegisterInstance(configuration).As<ITentacleConfiguration>();
+            builder.RegisterModule<TentacleCommunicationsModule>();
+            var container = builder.Build();
+            return container;
+        }
+    }
+}

source/Octopus.Tentacle/Communications/TentacleCommunicationsModule.cs

@@ -25,7 +25,12 @@ protected override void Load(ContainerBuilder builder)
                 var configuration = c.Resolve<ITentacleConfiguration>();
                 var services = c.Resolve<IServiceFactory>();
 
-                bool.TryParse(Environment.GetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled), out var tcpKeepAliveEnabled);
+                if (!bool.TryParse(Environment.GetEnvironmentVariable(EnvironmentVariables.TentacleTcpKeepAliveEnabled), out var tcpKeepAliveEnabled))
+                {
+                    // Default to enabled if the environment variable is not provided
+                    tcpKeepAliveEnabled = true;
+                }
+
                 bool.TryParse(Environment.GetEnvironmentVariable(EnvironmentVariables.TentacleUseRecommendedTimeoutsAndLimits), out var useRecommendedTimeoutsAndLimits);
 
                 var halibutTimeoutsAndLimits = useRecommendedTimeoutsAndLimits