Symptoms

When attempting to mention a user, you are not able to click the user name to insert, or the search does not work as expected to find a user. You may also find this behaviour when working with other areas of Confluence that ask you to select a User.

The following appears in the atlassian-confluence.log (You may also see a similar stack trace in the console of your browser):

 -- url: /rest/prototype/1/search.json | userName: userName | referer: http://wiki/some/path/
java.lang.NullPointerException: userkey
    at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:204)
    at com.atlassian.sal.api.user.UserKey.<init>(UserKey.java:27)

Cause

The index is damaged or incomplete; and must be rebuilt.

Resolution

Because you'll need to shut down Confluence in order to re-build the content indices, you may wish to schedule the downtime outside your normal operating hours.

• Follow the instructions to How to Rebuild the Content Indexes From Scratch on Confluence Server
• After Confluence has been restarted, you may need to perform a manual re-index, as described in Content Index Administration

Always ensure you have a full back up of your Home Directory before making changes to it.