The is actually a 3.1.x bug.

When the extra data is stored in the hash table for each metric, the extra 
data strings are being overwritten.  The extra data needs to be added to each 
summary metric rather than trying to replace the entire strings field.

Created an attachment (id=131) [details]
Add each extra data individually

This has been fixed in trunk.  The attached patch is against the 3.1 branch is
has been proposed for backport

Created an attachment (id=132) [details]
Add each extra data element individually

this was fixed for 3.1.0 AFAIK

Fixed in Trunk and backported to the 3.1 branch.

seems like an incomplete fix was backported in this bug by :

r1355 | bnicholes | 2008-05-16 12:46:01 -0700 (Fri, 16 May 2008) | 7 lines

Add each extra data element individually to the summary metric node
rather than replacing the entire strings field. This also resolves a
memory leak issue while processing the metric XML data.

Reviewed by: bnicholes, bernardli

it has been reported though later that the same code will segfault while used by
an aggregator as detailed in :

http://www.mail-archive.com/ganglia-developers@lists.sourceforge.net/msg04584.html

This was a problem with process the tag when gmetad is not the authority.  A
fix
has been committed to trunk (#1633) and proposed for backport.

Created an attachment (id=151) [details]
backported fix for ganglia 3.1