Default polling workers to CPU-based connection count (Option B: CPU-scaled)

source/Octopus.Tentacle/Commands/RegisterMachineCommandBase.cs

@@ -177,11 +177,14 @@ async Task RegisterMachine(IOctopusSystemAsyncRepository systemRepository, IOcto
             }
 
             configuration.Value.AddOrUpdateTrustedOctopusServer(server);
+            configuration.Value.SetIsWorker(IsRegisteredAsWorker);
             VoteForRestart();
 
             log.Info("Machine registered successfully");
         }
 
+        protected virtual bool IsRegisteredAsWorker => false;
+
         protected abstract void CheckArgs();
 
         protected abstract void EnhanceOperation(TRegistrationOperationType registerOperation);

source/Octopus.Tentacle/Commands/RegisterWorkerCommandBase.cs

@@ -29,6 +29,8 @@ public RegisterWorkerCommandBase(Lazy<TRegisterWorkerOperation> lazyRegisterMach
             Options.Add("workerpool=", "The worker pool name, slug or Id to add the machine to - e.g., 'Windows Pool'; specify this argument multiple times to add to multiple pools", s => workerpools.Add(s));
         }
 
+        protected override bool IsRegisteredAsWorker => true;
+
         protected override void CheckArgs()
         {
             if (workerpools.Count == 0 || string.IsNullOrWhiteSpace(workerpools.First()))

source/Octopus.Tentacle/Communications/HalibutInitializer.cs

@@ -115,19 +115,21 @@ void AddPollingEndpoints()
             }
         }
 
-        const int MaximumPollingConnectionCount = 8;
-
+        const uint MinimumPollingConnectionCount = 2;
+        const uint MaximumPollingConnectionCount = 8;
+
         uint GetPollingConnectionCount()
         {
-            //Open multiple polling connections if the env var is set to a non-zero/negative number
-            var connectionCount = 1u;
+            // Default to one connection per CPU core (clamped to [min, max]) for workers; deployment targets stay at 1
+            var connectionCount = configuration.IsWorker
+                ? (uint)Math.Clamp(Environment.ProcessorCount, MinimumPollingConnectionCount, MaximumPollingConnectionCount)
+                : 1u;
             if (uint.TryParse(Environment.GetEnvironmentVariable(EnvironmentVariables.TentaclePollingConnectionCount), out var count))
             {
                 log.InfoFormat("Requested polling connection count: {0}", count);
                 connectionCount = count;
             }
 
-            //Coerce the requested value as it might be outside our max & min
             switch (connectionCount)
             {
                 case > MaximumPollingConnectionCount:

source/Octopus.Tentacle/Configuration/ITentacleConfiguration.cs

@@ -75,6 +75,8 @@ public interface ITentacleConfiguration
 
         bool IsRegistered { get; }
 
+        bool IsWorker { get; }
+
         void WriteTo(IWritableKeyValueStore outputStore, IEnumerable<string> excluding);
     }
 
@@ -92,6 +94,8 @@ public interface IWritableTentacleConfiguration : ITentacleConfiguration
 
         bool SetIsRegistered(bool isRegistered = true);
 
+        bool SetIsWorker(bool isWorker = true);
+
         /// <summary>
         /// Sets the IP address to listen on.
         /// </summary>

source/Octopus.Tentacle/Configuration/TentacleConfiguration.cs

@@ -19,6 +19,7 @@ namespace Octopus.Tentacle.Configuration
     internal class TentacleConfiguration : ITentacleConfiguration
     {
         internal const string IsRegisteredSettingName = "Tentacle.Services.IsRegistered";
+        internal const string IsWorkerSettingName = "Tentacle.Services.IsWorker";
         internal const string ServicesPortSettingName = "Tentacle.Services.PortNumber";
         internal const string ServicesListenIPSettingName = "Tentacle.Services.ListenIP";
         internal const string ServicesNoListenSettingName = "Tentacle.Services.NoListen";
@@ -70,6 +71,8 @@ public IEnumerable<string> TrustedOctopusThumbprints
 
         public bool IsRegistered => settings.Get(IsRegisteredSettingName, false);
 
+        public bool IsWorker => settings.Get(IsWorkerSettingName, false);
+
         public void WriteTo(IWritableKeyValueStore outputStore, IEnumerable<string> excluding)
         {
             excluding = new HashSet<string>(excluding);
@@ -191,6 +194,11 @@ public bool SetIsRegistered(bool isRegistered = true)
             return settings.Set(IsRegisteredSettingName, isRegistered);
         }
 
+        public bool SetIsWorker(bool isWorker = true)
+        {
+            return settings.Set(IsWorkerSettingName, isWorker);
+        }
+
         public bool SetListenIpAddress(string? address)
         {
             return settings.Set(ServicesListenIPSettingName, address);