If you have lots of performance graphs for a node in OpenNMS, sometimes you get a blank page showing them.

Especially when choosing a large time period like Last Month or Last Year.

The reason for a blank page is found in the OpenNMS logfiles.

"413 Requested entity too large"

Just increase the requestHeaderSize in /etc/opennms/opennms.properties until the graphs show up.

# This sets the request header size for jetty.
# The default value is 4000 bytes.
#org.opennms.netmgt.jetty.requestHeaderSize=4000