Hi,
I used your config for collectd. My collectd sends metrics to graphite. I had this error in logs :
"format_graphite: target buffer too small"
I have done some search and I saw this discussion :
https://www.mail-archive.com/[email protected]/msg02600.html
Florian Forster is the main developper of collectd and he said :

...which seems to have 14 data sources. I'm not sure whether that's
excessive or not and I didn't write the plugin so I'm not entirely
sure what it does. :)

163 of 195 types that collectd defines by default have a single data
source. Of the non-legacy types, only "load" has more than two. I'm currently
thinking about eventually removing the support for multiple data sources from
collectd entirely

My issue is caused by the type.db with return too many metrics. So I splitted the type and it works well :
database_stats numbackends:GAUGE:0:u
database_stats_xact xact_rollback:COUNTER:0:u, xact_commit:COUNTER:0:u
database_stats_blks blks_read:COUNTER:0:u, blks_hit:COUNTER:0:u
database_stats_tup tup_returned:COUNTER:0:u, tup_fetched:COUNTER:0:u, tup_inserted:COUNTER:0:u, tup_updated:COUNTER:0:u, tup_deleted:COUNTER:0:u