It's a well known fact that Sitecore uses an old and somewhat customised version of log4net. This can make integrations with other libraries such as Sumo Logic difficult as the log4net APIs have changed.
To work around this issue a new log4net Appender must be created to accept log messages in the old API format and forward them on. The high level solution is as follows:
- Create a new Sitecore Appender responsible for buffering and forwarding on messages to the SumoLogicMessageSender.cs
- Patch in the new Appender to Sitecore
Create a new Sitecore Appender
Create a new log4net Appender that derives from the AppenderSkeleton class in the Sitecore.Logging assembly.