Symptoms

On startup, the following appears in the atlassian-confluence.log:

Parent Classloader: org.apache.catalina.loader.StandardClassLoader@df1832].
log4j:ERROR Could not instantiate appender named "confluencelog".
log4j:ERROR A "com.atlassian.confluence.logging.ConfluenceHomeLogAppender" object is not assignable to a "org.apache.log4j.Appender" variable.
log4j:ERROR The class "org.apache.log4j.Appender" was loaded by
log4j:ERROR [com.atlassian.plugin.classloader.PluginClassLoader@6044d5] whereas object of type
log4j:ERROR "com.atlassian.confluence.logging.ConfluenceHomeLogAppender" was loaded by [WebappClassLoader
delegate: false
repositories: /WEB-INF/classes/

The error does not cause any visible effect in Confluence performance or operation.

Cause

The error can be caused by a plugin that tries to assign a com.atlassian.confluence.logging.ConfluenceHomeLogAppender object to the org.apache.log4j.Appender.

Resolution

Ensure that all plugins are up to date:

1. Using the Universal Plugin Manager, identify outdated plugins.

   Prior to the Universal Plugin Manager, it may be necessary to uninstall old plugins one by one to determine which plugin is responsible. You can track old plugins from the database by their last modification date:

   select plugindataid, pluginkey, filename, lastmoddate from plugindata ORDER BY lastmoddate;
   

2. Remove the outdated plugin. This may be done directly from Administration >> Plugins. If that does not work, refer to How to manually remove malfunctioning add-ons.