MVC 4 Azure web role: Error 500 when adding the “tracing” element to web.config

Question

I'm trying to add diagnostics to an Azure web role by following the example found here: https://www.windowsazure.com/en-us/develop/net/common-tasks/diagnostics/

When I add the tracing element under system.webserver , I see an error when running the website. The error can be seen even before a breakpoint in OnStart is hit.

Any ideas?

Here is my web.config file with the problematic section commented out:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>    
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <system.diagnostics>
    <trace>
      <listeners>
        <add type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=1.8.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="AzureDiagnostics">
        </add>
      </listeners>
    </trace>
  </system.diagnostics>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=aspnet_d368ef657c124d629b2577cb9775791c;Integrated Security=True;MultipleActiveResultSets=True" providerName="System.Data.SqlClient" />
  </connectionStrings>
  <appSettings>
    <add key="webpages:Version" value="2.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="PreserveLoginUrl" value="true" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  </appSettings>
  <system.web>
    <customErrors mode="Off"></customErrors>
    <compilation debug="true" targetFramework="4.0" />
    <authentication mode="Forms">
      <forms loginUrl="~/Account/Login" timeout="2880" />
    </authentication>
    <pages>
      <namespaces>
        <add namespace="System.Web.Helpers" />
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Optimization" />
        <add namespace="System.Web.Routing" />
        <add namespace="System.Web.WebPages" />
      </namespaces>
    </pages>
    <machineKey decryption="AES" decryptionKey="F7FA540B4DFD82E5BB196B95D15FF81F740A8B17F626BAF1D0889905ACBF0B60" validation="SHA1" validationKey="740A8B17F626BAF1D0889905ACBF0B609712CDA49DE62168764FF0DCE537184F0535D5D9AD66DEDC740A8B17F626BAF1D0889905ACBF0B609712CDA497DC1ABF" />
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false" />
    <modules runAllManagedModulesForAllRequests="true" />
    <handlers>
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
    <!--<tracing>
      <traceFailedRequests>
        <add path="*">
          <traceAreas>
            <add provider="ASP" verbosity="Verbose" />
            <add provider="ASPNET" areas="Infrastructure,Module,Page,AppServices" verbosity="Verbose" />
            <add provider="ISAPI Extension" verbosity="Verbose" />
            <add provider="WWW Server"
            areas="Authentication,
                Security,
                Filter,
                StaticFile,
                CGI,
                Compression,
                Cache,
                RequestNotifications,
                Module"
            verbosity="Verbose" />
          </traceAreas>
          <failureDefinitions statusCodes="400-599" />
        </add>
      </traceFailedRequests>
    </tracing>-->
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-4.0.0.0" newVersion="4.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
  </entityFramework>
</configuration>

Answer 1

Here is how I solved the issue:

Suddenly the server started printing verbose info about the 500 error (I don't know why, I don't think I changed anything), and then I discovered that the actual error was:

HTTP Error 500.19:

Cannot add duplicate collection entry of type 'add' with unique key attribute 'path' set to '*'

The solution to this was to add the following line before the add tag:

<remove path="*"/>

So now the tracing tag looks like this:

<tracing>
      <traceFailedRequests>
        <remove path="*"/>
        <add path="*">
          <traceAreas>
            <add provider="ASP" verbosity="Verbose" />
            <add provider="ASPNET" areas="Infrastructure,Module,Page,AppServices" verbosity="Verbose" />
            <add provider="ISAPI Extension" verbosity="Verbose" />
            <add provider="WWW Server"
            areas="Authentication,
                Security,
                Filter,
                StaticFile,
                CGI,
                Compression,
                Cache,
                RequestNotifications,
                Module"
            verbosity="Verbose" />
          </traceAreas>
          <failureDefinitions statusCodes="400-599" />
        </add>
      </traceFailedRequests>
    </tracing>

and this seems to work fine.

Answer 2

I noticed that you're referencing Microsoft.WindowsAzure.Diagnostics Version=1.8.0.0 which comes part of the October Azure SDK to get the Azure listener. Do you have the Storage client library 1.7 included in your project? The Azure diagnostics library 1.8 relies on the older storage client library 1.7 (not 2.0 which was released with the sdk)