Do not treat 'did not find initialized language workers' as a user exception (#5803)

* do not treat 'did not find initialized language workers' as a user code exception

* update comment

* typo

* remove full try catch

Author: mhoeger

src/WebJobs.Script/Workers/Rpc/FunctionRegistration/RpcFunctionInvocationDispatcher.cs

@@ -234,23 +234,17 @@ public async Task ShutdownAsync()
 
         public async Task InvokeAsync(ScriptInvocationContext invocationContext)
         {
-            try
+            // This could throw if no initialized workers are found. Shut down instance and retry.
+            IEnumerable<IRpcWorkerChannel> workerChannels = await GetInitializedWorkerChannelsAsync();
+            var rpcWorkerChannel = _functionDispatcherLoadBalancer.GetLanguageWorkerChannel(workerChannels, _maxProcessCount);
+            if (rpcWorkerChannel.FunctionInputBuffers.TryGetValue(invocationContext.FunctionMetadata.FunctionId, out BufferBlock<ScriptInvocationContext> bufferBlock))
             {
-                IEnumerable<IRpcWorkerChannel> workerChannels = await GetInitializedWorkerChannelsAsync();
-                var rpcWorkerChannel = _functionDispatcherLoadBalancer.GetLanguageWorkerChannel(workerChannels, _maxProcessCount);
-                if (rpcWorkerChannel.FunctionInputBuffers.TryGetValue(invocationContext.FunctionMetadata.FunctionId, out BufferBlock<ScriptInvocationContext> bufferBlock))
-                {
-                    _logger.LogDebug("Posting invocation id:{InvocationId} on workerId:{workerChannelId}", invocationContext.ExecutionContext.InvocationId, rpcWorkerChannel.Id);
-                    rpcWorkerChannel.FunctionInputBuffers[invocationContext.FunctionMetadata.FunctionId].Post(invocationContext);
-                }
-                else
-                {
-                    throw new InvalidOperationException($"Function:{invocationContext.FunctionMetadata.Name} is not loaded by the language worker: {rpcWorkerChannel.Id}");
-                }
+                _logger.LogDebug("Posting invocation id:{InvocationId} on workerId:{workerChannelId}", invocationContext.ExecutionContext.InvocationId, rpcWorkerChannel.Id);
+                rpcWorkerChannel.FunctionInputBuffers[invocationContext.FunctionMetadata.FunctionId].Post(invocationContext);
             }
-            catch (Exception invokeEx)
+            else
             {
-                invocationContext.ResultSource.TrySetException(invokeEx);
+                throw new InvalidOperationException($"Function:{invocationContext.FunctionMetadata.Name} is not loaded by the language worker: {rpcWorkerChannel.Id}");
             }
         }