more error handling and docs

src/Ocelot/Errors/OcelotErrorCode.cs

@@ -42,5 +42,6 @@
         RequestCanceled = 37,
         ConnectionToDownstreamServiceError = 38,
         CouldNotFindLoadBalancerCreator = 39,
+        ErrorInvokingLoadBalancerCreator = 40,
     }
 }

src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessionsCreator.cs

@@ -4,15 +4,16 @@
     using Ocelot.Configuration;
     using Ocelot.Infrastructure;
     using Ocelot.ServiceDiscovery.Providers;
+    using Ocelot.Responses;
 
     public class CookieStickySessionsCreator : ILoadBalancerCreator
     {
-        public ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
+        public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
         {
             var loadBalancer = new RoundRobin(async () => await serviceProvider.Get());
             var bus = new InMemoryBus<StickySession>();
-            return new CookieStickySessions(loadBalancer, reRoute.LoadBalancerOptions.Key,
-                reRoute.LoadBalancerOptions.ExpiryInMs, bus);
+            return new OkResponse<ILoadBalancer>(new CookieStickySessions(loadBalancer, reRoute.LoadBalancerOptions.Key,
+                reRoute.LoadBalancerOptions.ExpiryInMs, bus));
         }
 
         public string Type => nameof(CookieStickySessions);

src/Ocelot/LoadBalancer/LoadBalancers/DelegateInvokingLoadBalancerCreator.cs

@@ -3,6 +3,7 @@
     using System;
     using Ocelot.Configuration;
     using Ocelot.ServiceDiscovery.Providers;
+    using Ocelot.Responses;
 
     public class DelegateInvokingLoadBalancerCreator<T> : ILoadBalancerCreator
         where T : ILoadBalancer
@@ -15,9 +16,17 @@
             _creatorFunc = creatorFunc;
         }
 
-        public ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
+        public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
         {
-            return _creatorFunc(reRoute, serviceProvider);
+            try
+            {
+                return new OkResponse<ILoadBalancer>(_creatorFunc(reRoute, serviceProvider));
+
+            }
+            catch (Exception e)
+            {
+                return new ErrorResponse<ILoadBalancer>(new ErrorInvokingLoadBalancerCreator(e));
+            }
         }
 
         public string Type => typeof(T).Name;

src/Ocelot/LoadBalancer/LoadBalancers/ErrorInvokingLoadBalancerCreator.cs

@@ -0,0 +1,12 @@
+namespace Ocelot.LoadBalancer.LoadBalancers
+{
+    using System;
+    using Errors;
+
+    public class ErrorInvokingLoadBalancerCreator : Error
+    {
+        public ErrorInvokingLoadBalancerCreator(Exception e) : base($"Error when invoking user provided load balancer creator function, Message: {e.Message}, StackTrace: {e.StackTrace}", OcelotErrorCode.ErrorInvokingLoadBalancerCreator)
+        {
+        }
+    }
+}

src/Ocelot/LoadBalancer/LoadBalancers/ILoadBalancerCreator.cs

@@ -1,11 +1,12 @@
-using Ocelot.Configuration;
-using Ocelot.ServiceDiscovery.Providers;
-
-namespace Ocelot.LoadBalancer.LoadBalancers
+namespace Ocelot.LoadBalancer.LoadBalancers
 {
+    using Ocelot.Responses;
+    using Ocelot.Configuration;
+    using Ocelot.ServiceDiscovery.Providers;
+
     public interface ILoadBalancerCreator
     {
-        ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider);
+        Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider);
         string Type { get; }
     }
 }

src/Ocelot/LoadBalancer/LoadBalancers/LeastConnectionCreator.cs

@@ -2,12 +2,13 @@
 {
     using Ocelot.Configuration;
     using Ocelot.ServiceDiscovery.Providers;
+    using Ocelot.Responses;
 
     public class LeastConnectionCreator : ILoadBalancerCreator
     {
-        public ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
+        public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
         {
-            return new LeastConnection(async () => await serviceProvider.Get(), reRoute.ServiceName);
+            return new OkResponse<ILoadBalancer>(new LeastConnection(async () => await serviceProvider.Get(), reRoute.ServiceName));
         }
 
         public string Type => nameof(LeastConnection);

src/Ocelot/LoadBalancer/LoadBalancers/LoadBalancerFactory.cs

@@ -35,8 +35,14 @@
                 return new ErrorResponse<ILoadBalancer>(new CouldNotFindLoadBalancerCreator($"Could not find load balancer creator for Type: {requestedType}, please check your config specified the correct load balancer and that you have registered a class with the same name."));
             }
 
-            var createdLoadBalancer = applicableCreator.Create(reRoute, serviceProvider);
-            return new OkResponse<ILoadBalancer>(createdLoadBalancer);
+            var createdLoadBalancerResponse = applicableCreator.Create(reRoute, serviceProvider);
+
+            if (createdLoadBalancerResponse.IsError)
+            {
+                return new ErrorResponse<ILoadBalancer>(createdLoadBalancerResponse.Errors);
+            }
+
+            return new OkResponse<ILoadBalancer>(createdLoadBalancerResponse.Data);
         }
     }
 }

src/Ocelot/LoadBalancer/LoadBalancers/NoLoadBalancerCreator.cs

@@ -2,12 +2,13 @@
 { 
     using Ocelot.Configuration;
     using Ocelot.ServiceDiscovery.Providers;
+    using Ocelot.Responses;
 
     public class NoLoadBalancerCreator : ILoadBalancerCreator
     {
-        public ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
+        public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
         {
-            return new NoLoadBalancer(async () => await serviceProvider.Get());
+            return new OkResponse<ILoadBalancer>(new NoLoadBalancer(async () => await serviceProvider.Get()));
         }
 
         public string Type => nameof(NoLoadBalancer);

src/Ocelot/LoadBalancer/LoadBalancers/RoundRobinCreator.cs

@@ -2,12 +2,13 @@
 {
     using Ocelot.Configuration;
     using Ocelot.ServiceDiscovery.Providers;
-    
+    using Ocelot.Responses;
+
     public class RoundRobinCreator : ILoadBalancerCreator
     {
-        public ILoadBalancer Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
+        public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
         {
-            return new RoundRobin(async () => await serviceProvider.Get());
+            return new OkResponse<ILoadBalancer>(new RoundRobin(async () => await serviceProvider.Get()));
         }
 
         public string Type => nameof(RoundRobin);

src/Ocelot/Responder/ErrorsToHttpStatusCodeMapper.cs

@@ -46,7 +46,8 @@ namespace Ocelot.Responder
             }
 
             if (errors.Any(e => e.Code == OcelotErrorCode.UnableToCompleteRequestError
-                || e.Code == OcelotErrorCode.CouldNotFindLoadBalancerCreator))
+                || e.Code == OcelotErrorCode.CouldNotFindLoadBalancerCreator
+                || e.Code == OcelotErrorCode.ErrorInvokingLoadBalancerCreator))
             {
                 return 500;
             }