ASP.Net Core logs Kestrel errors without details

Question

I have an ASP.NET Core 3.1 web application with API controllers and SignalR. Logging framework is NLog. I receive some strange errors on production server:

ERROR|Microsoft.AspNetCore.Server.Kestrel|Connection id "...", Request id "...": An unhandled exception was thrown by the application. Object reference not set to an instance of an object.

They do not have any details. My logging params are:

  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "Console": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
  }

My NLog config:

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      autoReload="true"
      internalLogLevel="Warn"
      internalLogFile="...">


  <!-- the targets to write to -->
  <targets>
    <!-- write logs to file  -->
    <target xsi:type="File" name="allfile" fileName="..."
            layout="${longdate}|${event-properties:item=EventId.Id}|${uppercase:${level}}|${logger}|${message} ${exception}" />

    <!-- another file log, only own logs. Uses some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="..."
            layout="${longdate}|${event-properties:item=EventId.Id}|${uppercase:${level}}|${logger}|${message} ${exception}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" />

    <!-- write to the void aka just remove -->
    <target xsi:type="Null" name="blackhole" />
  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Warn" writeTo="allfile" />

    <!--Skip Microsoft logs and so log only own logs-->
    <logger name="Microsoft.*" minlevel="info" writeTo="blackhole" final="true" />
    <logger name="*" minlevel="Warn" writeTo="ownFile-web" />
  </rules>
</nlog>

Is there a way to get more information about these errors? Should I implement some exception filter? Thank you!

Answer 1

I have found the answer to my own question. I need to use "${exception:format=tostring}" format to get exception details in NLog log.