What to do if Elmah can't reach the database to log an exception?

问题

OK, apparently related questions dont seem to address this directly. An exception reaches Elmah, maybe a repository cant reach a database, but then neither can Elmah reach that database. Even if they target different servers, maybe its a network problem.

Is there a way to configure fallback logs for Elmah for cases like this, e.g. a text file, message queue, email, sms, etc? If so, where do I start looking to do this, excpt for now the Elmah source code.

回答1:

I am usually not so concerned about that: If the DB is not running then my application is not running and I have no exceptions to log anyway. But if this is an issue for you then you could consider to use the XmlFileErrorLog.

As far as I can tell you cannot use more then one log destination and there is nothing like a fallback. You could however configure email notifications, but then you would get all exceptions by email as well.

Here is quite a nice article about elmah.

回答2:

I released a composite errorlog which address exactly this issue.
You can install it via Nuget or copy it from sources into your projects.

Basic usage from config file :

<configuration>
  <configSections>
    <sectionGroup name="elmah">
      <section name="security" requirePermission="false" type="Elmah.SecuritySectionHandler, Elmah" />
      <section name="errorLog" requirePermission="false" type="Elmah.FallbackErrorLogSectionHandler, Elmah.FallbackErrorLog" />
      <section name="errorMail" requirePermission="false" type="Elmah.ErrorMailSectionHandler, Elmah" />
      <section name="errorFilter" requirePermission="false" type="Elmah.ErrorFilterSectionHandler, Elmah" />
    </sectionGroup>
  </configSections>
  <elmah>
    <errorLog type="Elmah.FallbackErrorLog, Elmah.FallbackErrorLog" >
        <add type="Elmah.SqlErrorLog, Elmah" connectionStringName="DB_ELMAH"  applicationName="Blog" />
        <add type="Elmah.XmlFileErrorLog, Elmah" logPath="~/App_Data/Logs" />
        <add type="Elmah.MemoryErrorLog, Elmah" size="30" />
    </errorLog>
  </elmah>
</configuration>

来源：https://stackoverflow.com/questions/3391494/what-to-do-if-elmah-cant-reach-the-database-to-log-an-exception