System.NullReferenceException Microsoft.AspNetCore.Routing.Matching.DfaMatcher.<SelectEndpointWithPoliciesAsync> (Intermittent Issue)

[shama-ak]

Describe the bug
There is an intermittent System.NullReferenceException. The exception occurs in the SelectEndpointWithPoliciesAsync method. There are no specific steps to reproduce the issue, but telemetry data has shown the occurrence of this exception.

Expected behavior
The method should execute without throwing a NullReferenceException.

Stack Trace
ODataExceptionHandlerMiddleware: Unexpected error Exception: System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.AspNetCore.Routing.Matching.DfaMatcher.d__13.MoveNext() +0xcc
at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.<g__AwaitMatch|10_1>d.MoveNext() +0x65
at Microsoft.AspNet.OData.Batch.ODataBatchMiddleware.d__2.MoveNext() +0x15f

[habbes]

Given that it's an intermittent error, it could be a race condition in the batch handler or shared state that's getting mutated in different threads. Do you have any information about the kind of requests where you observed this behaviour?

[shama-ak]

Our telemetry shows these 6 requests being processed within same timeframe:

TIMESTAMP	Request	HttpStatus
2024-06-11 15:56:08.1761397	https://foo.com/api/data/v9.0/accounts(GUID_Value)/new_acc_con0611241/$ref	204 No Content
2024-06-11 15:56:08.2972903	https://foo.com/api/data/v9.0/accounts	204 No Content
2024-06-11 15:56:08.3907339	https://foo.com/api/data/v9.0/accounts(GUID_Value)	200 OK
2024-06-11 15:56:08.5140539	https://foo.com/api/data/v9.0/accounts	204 No Content
2024-06-11 15:56:08.5376303	https://foo.com/api/data/v9.0/accounts?$filter=length(name) eq 19	501 Not Implemented
2024-06-11 15:56:08.5643568	https://foo.com/api/data/v9.0/accounts?$filter=trim(name) eq 'firstname lastname'	500 Internal Server Error