Error handling for http proxying (#9342)

Author: satvu

release_notes.md

@@ -7,3 +7,4 @@
 - Patch Durable Functions Extension version check (https://github.com/Azure/azure-functions-host/pull/9331)
 - Update Java Worker Version to [2.12.0](https://github.com/Azure/azure-functions-java-worker/releases/tag/2.12.0)
 - Remove feature flag for http proxying (https://github.com/Azure/azure-functions-host/pull/9341)
+- Add error handling for http proxying failure scenarios (https://github.com/Azure/azure-functions-host/pull/9342)

src/WebJobs.Script.Grpc/Channel/GrpcWorkerChannel.cs

@@ -963,24 +963,23 @@ internal async Task InvokeResponse(InvocationResponse invokeResponse)
             {
                 if (invokeResponse.Result.IsInvocationSuccess(context.ResultSource, capabilityEnabled))
                 {
-                    if (IsHttpProxyingWorker)
+                    _metricsLogger.LogEvent(string.Format(MetricEventNames.WorkerInvokeSucceeded, Id));
+
+                    try
                     {
-                        if (context.Properties.TryGetValue(ScriptConstants.HttpProxyTask, out Task<ForwarderError> httpProxyTask))
+                        if (IsHttpProxyingWorker)
                         {
-                            ForwarderError httpProxyTaskResult = await httpProxyTask;
-
-                            if (httpProxyTaskResult is not ForwarderError.None)
+                            if (context.Properties.TryGetValue(ScriptConstants.HttpProxyTask, out Task<ForwarderError> httpProxyTask))
                             {
-                                // TODO: Understand scenarios where function invocation succeeds but there is an error proxying
-                                // need to investigate different ForwarderErrors and consider how they will be relayed through other services and to users
+                                ForwarderError httpProxyTaskResult = await httpProxyTask;
+
+                                if (httpProxyTaskResult is not ForwarderError.None)
+                                {
+                                    throw new InvalidOperationException($"Failed to proxy request with ForwarderError: {httpProxyTaskResult}");
+                                }
                             }
                         }
-                    }
-
-                    _metricsLogger.LogEvent(string.Format(MetricEventNames.WorkerInvokeSucceeded, Id));
 
-                    try
-                    {
                         StringBuilder logBuilder = new StringBuilder();
                         bool usedSharedMemory = false;