NullReferenceException at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.FunctionInvocationFilterInvoker.InvokeAsync(Object instance,Object[] arguments)

#### Investigative information

Please provide the following:

- Timestamp: 27-02-2018 7:36 GMT
- Function App version (1.0 or 2.0-beta): 1.0
- Invocation ID: f0639e62-2d56-4546-8969-9f2c12fc899c
- Region: west-europe

#### Related information

We see this exception when sending a lot of messages through the function. In this case the db was pegged at 100% DTU usage so that very likely caused the error. However the stack trace is not useful and doesn't contain any of our code. Which makes this very difficult to diagnose. This isn't a major issue as the function normally executes correctly after a few attempts or if we scale the database but I would like to be able to get better stacktraces

CSharp Function
Using ServiceBus bindings

StackTrace from kudu

```
Exception while executing function: QueueChatPushNotifications
Microsoft.Azure.WebJobs.Host.FunctionInvocationException : Exception while executing function: QueueChatPushNotifications ---> System.NullReferenceException : Object reference not set to an instance of an object.
at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.FunctionInvocationFilterInvoker.InvokeAsync(Object instance,Object[] arguments)
at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.InvokeAsync(IFunctionInvoker invoker,ParameterHelper parameterHelper,CancellationTokenSource timeoutTokenSource,CancellationTokenSource functionCancellationTokenSource,Boolean throwOnTimeout,TimeSpan timerInterval,IFunctionInstance instance)
at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithWatchersAsync(IFunctionInstance instance,ParameterHelper parameterHelper,TraceWriter traceWriter,CancellationTokenSource functionCancellationTokenSource)
at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)
at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)
End of inner exception
```

Stack Trace from App Insights

```
Microsoft.Azure.WebJobs.Host.FunctionInvocationException: Exception while executing function: QueueChatPushNotifications ---> System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.FunctionInvocationFilterInvoker.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__24.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__23.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task) at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__16.MoveNext()
--- End of inner exception stack trace ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__16.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.d__13.MoveNext()
```

Start with the FunctionExecutor.FunctionInvocationFilterInvoker.InvokeAsync entry point named in the Kudu and Application Insights traces, then compare the two stack traces and the reported high-throughput, 100% DTU condition. Done means the resulting failure can be diagnosed from its stack trace, including relevant user-code context, or the limitation is clearly documented.

Written by the indexing model from the issue text.