Symptoms

When Confluence try to load calendars on My Calendar page, Confluence would take a long time to load it and lead to 500 - GC overhead limit exceed on Team Calendars for Confluence 1.8.2 and prior it, while on Team Calendars for Confluence 1.9  Internal Server Error will be thrown on the UI level. Usually this is caused by user incorrectly configured the end date of event(s)

Here are the screenshots and the stack trace thrown in atlassian-confluence.log:

ERROR [http-8357-1] [opensymphony.xwork.util.CompoundRootAccessor] getProperty Caught an Ognl exception while getting property calendarHtml
 -- url: /confluence/calendar/mycalendar.action | userName: admin | referer: http://localhost:8357/confluence/dashboard.action | action: mycalendar
ognl.OgnlException: calendarHtml [java.lang.OutOfMemoryError: GC overhead limit exceeded]

2012-04-02 18:08:24,054 ERROR [http-8414-5] [[Standalone].[localhost].[/confluence].[noop]] log Servlet.service() for servlet noop threw exception
java.lang.OutOfMemoryError: Java heap space

Cause

A very long running event cause such behavior in Confluence

Diagnosis and Resolution

When such symptom occurred run the following diagnostic steps

1. Execute the following SQL query into your Confluence database

   SELECT * FROM bandana WHERE BANDANACONTEXT LIKE '%CALENDAR_%' AND BANDANAVALUE LIKE '<string>BEGIN:%';

   The above query would return all the ICS file of the installed calendar

2. Try to find following DTSTART and DTEND parameter on every event on each ICS

   Example: 

   DTSTART;VALUE=DATE:20120203
   DTEND;VALUE=DATE:20120204


   The above lines means that the event configured to run from 3rd of February, 2012

3. Try to find the long running event that may cause this issue. For example:

   DTSTART;VALUE=DATE:20120202
   DTEND;VALUE=DATE:29990203


   The above parameter stated that the event run from February 2012 to February 2999 

4. Modified the year of the date end correctly in shutdown mode
5. Restart Confluence