NLog seems to ignore config file location in .NET Core 3.1 Windows Service

Question

Type: Bug

NLog version: 4.7.2

NLog.Web/NLog.Web.AspNetCore version: 4.9.2

NLog.Extensions.Logging version: N/A

Platform: .NET Core 3.1

Current NLog config (xml or C#, if relevant)

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        autoReload="true"
        internalLogLevel="Warn"
        internalLogFile="internal.txt">
  <extensions>
    <!--enable NLog.Web for ASP.NET Core-->
    <add assembly="NLog.Web.AspNetCore"/>
  </extensions>

  <!-- define various log targets -->
  <targets>
    <target xsi:type="File"
            name="allOutput"
            fileName="${startupdir}\logs\SkyJack-Agent-All-${shortdate}.log"
            layout="${longdate} ${logger} ${uppercase:${level}} ${message} ${exception}" />
    <target xsi:type="File"
            name="ourOutput"
            fileName="${startupdir}\logs\SkyJack-Agent-OurOutput-${shortdate}.log"
            layout="${longdate} ${logger} ${uppercase:${level}} ${message} ${exception}" />
    <target xsi:type="File"
            name="errorsOnly"
            fileName="${startupdir}\logs\SkyJack-Agent-ErrorsOnly-${shortdate}.log"
            layout="${longdate} ${logger} ${uppercase:${level}} ${message} ${exception}" />
    <target name="console" xsi:type="ColoredConsole" layout="${longdate} ${pad:padding=5:inner=-${level}-} ${message}"
                useDefaultRowHighlightingRules="false" >
      <highlight-row condition="level==LogLevel.Trace" foregroundColor="Gray" />
      <highlight-row condition="level==LogLevel.Debug" foregroundColor="DarkGray" />
      <highlight-word text="-Info-"  foregroundColor="DarkGreen" />
      <highlight-word text="-Warn-"  foregroundColor="DarkYellow" />
      <highlight-word text="-Error-"  foregroundColor="DarkMagenta" />
      <highlight-word text="-Fatal-"  foregroundColor="DarkRed" backgroundColor="White"/>
    </target>
  </targets>

  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Debug" writeTo="console" />
    <logger name="*" minlevel="Trace" writeTo="allOutput" />
    <logger name="*" minlevel="Error" writeTo="errorsOnly" />    

    <!--Skip Microsoft logs - no writeTo attribute-->
    <logger name="Microsoft.*" minlevel="Trace" final="true" />
    <logger name="*" minlevel="Trace" writeTo="ourOutput" />
  </rules>
</nlog>

I am using NLog in a .NET Core web service published as single file and attempting to install it as a service. NLog works fine when I run it normally, however when running as a service it needs to be told where to find the config file, which I am accomplishing with:

            var pathToExe = Process.GetCurrentProcess().MainModule.FileName;
            var pathToContentRoot = Path.GetDirectoryName(pathToExe);

            NLog.LogManager.Configuration = new NLog.Config.XmlLoggingConfiguration(Path.Combine(pathToContentRoot, "nlog.config"));
            var logger = NLog.Web.NLogBuilder.ConfigureNLog(NLog.LogManager.Configuration).GetCurrentClassLogger();

And the content root with:

                builder.UseWindowsService().UseContentRoot(pathToContentRoot);

This appears to work, at least at first, and generates some log output, enough to see that I am setting the content root successfully:

2020-05-28 15:42:20.5932 SkyJack.Agent.Program INFO ... Initializing SkyJack Agent with content root G:\MSGPS2\SkyJack\SkyJack\src\SkyJack.Agent\bin\Release\netcoreapp3.1\publish... 
2020-05-28 15:42:20.6373 SkyJack.Agent.Program TRACE Entering CreateWebHostBuilder() 
2020-05-28 15:42:20.8023 SkyJack.Agent.Program TRACE Returned from CreateWebHostBuilder() 
2020-05-28 15:42:20.8023 SkyJack.Agent.Program TRACE Entering builder.Build() 
2020-05-28 15:42:20.9446 SkyJack.Agent.Program TRACE Returned from builder.Build()

Eventually, however, it throws an exception:

Log Name:      Application
Source:        ServerManagerAgent
Date:          5/28/2020 3:54:04 PM
Event ID:      6
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      HPZEE.redmond.corp.microsoft.com
Description:
Category: Microsoft.AspNetCore.Hosting.Diagnostics
EventId: 6

Application startup exception

Exception: 
System.IO.FileNotFoundException: Failed to load NLog LoggingConfiguration. Searched the following locations:
- C:\WINDOWS\TEMP\.net\ServerManagerAgent\31dyvwga.rkl\nlog.config

File name: 'nlog.config'
   at NLog.LogFactory.LoadConfiguration(String configFile, Boolean optional)
   at NLog.LogFactory.LoadConfiguration(String configFile)
   at NLog.LogManager.LoadConfiguration(String configFile)
   at NLog.Web.NLogBuilder.ConfigureNLog(String configFileName)
   at WebAppService.Startup.Configure(IApplicationBuilder app)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.<Build>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.Extensions.DependencyInjection.AutoRegisterMiddleware.<>c__DisplayClass4_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter.<>c__DisplayClass0_0.<Configure>g__MiddlewareFilterBuilder|0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)

Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="ServerManagerAgent" />
    <EventID Qualifiers="0">6</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>0</Task>
    <Opcode>0</Opcode>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2020-05-28T22:54:04.0041305Z" />
    <EventRecordID>61154</EventRecordID>
    <Correlation />
    <Execution ProcessID="0" ThreadID="0" />
    <Channel>Application</Channel>
    <Computer>HPZEE.redmond.corp.microsoft.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>Category: Microsoft.AspNetCore.Hosting.Diagnostics
EventId: 6

Application startup exception

Exception: 
System.IO.FileNotFoundException: Failed to load NLog LoggingConfiguration. Searched the following locations:
- C:\WINDOWS\TEMP\.net\ServerManagerAgent\31dyvwga.rkl\nlog.config

File name: 'nlog.config'
   at NLog.LogFactory.LoadConfiguration(String configFile, Boolean optional)
   at NLog.LogFactory.LoadConfiguration(String configFile)
   at NLog.LogManager.LoadConfiguration(String configFile)
   at NLog.Web.NLogBuilder.ConfigureNLog(String configFileName)
   at WebAppService.Startup.Configure(IApplicationBuilder app)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.&lt;&gt;c__DisplayClass4_0.&lt;Build&gt;b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.&lt;&gt;c__DisplayClass13_0.&lt;UseStartup&gt;b__2(IApplicationBuilder app)
   at Microsoft.Extensions.DependencyInjection.AutoRegisterMiddleware.&lt;&gt;c__DisplayClass4_0.&lt;Configure&gt;b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter.&lt;&gt;c__DisplayClass0_0.&lt;Configure&gt;g__MiddlewareFilterBuilder|0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.&lt;&gt;c__DisplayClass0_0.&lt;Configure&gt;b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
</Data>
  </EventData>
</Event>

WebAppService.Startup.Configure() is calling NLog.Web.NLogBuilder.ConfigureNLog() again, presumably with just "nlog.config" instead of the location or LoggerConfiguration object that I passed in to begin with.

Is there any way to get it to use the location or configuration that I've already specified and loaded?

I think this bug report should belong to github.com/NLog/NLog/issues/new?template=bug_report.md — Julian

Todd Heckel-MSFT Todd Heckel-MSFT · Accepted Answer · 2020-05-29T00:17:28

I got it working with:

NLog.LogManager.LogFactory.SetCandidateConfigFilePaths(new List<string> { $"{Path.Combine(pathToContentRoot, "nlog.config")}" });
var logger = NLog.Web.NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();

NLog seems to ignore config file location in .NET Core 3.1 Windows Service

1 Answers