I turned logging up to high and got this in the cacti log
Apache log shows thisCACTI2RRD: /usr/bin/rrdtool graph - --imgformat=PNG --start=-300 --end=-5 --title="xyxyxy Router - Traffic ether1 (xyxyxy)"
--rigid --base=1000 --height=120 --width=500 --x-grid SECOND:30:MINUTE:1:SECOND:30:0:%M:%S --alt-autoscale-max
--lower-limit=0 --vertical-label="bits per second" --slope-mode --font TITLE:10: --font AXIS:6: --font LEGEND:8:
--font UNIT:6: DEF:a="/var/www/html/plugins/realtime/cache/realtime_7694_5.rrd":traffic_in:AVERAGE
DEF:b="/var/www/html/plugins/realtime/cache/realtime_7694_5.rrd":traffic_out:AVERAGE CDEF:cdefa=a,8,*
CDEF:cdeff=b,8,* CDEF:cdefba=TIME,1359057395,GT,a,a,UN,0,a,IF,IF,TIME,1359057395,GT,b,b,UN,0,b,IF,IF,+,8,*
AREA:cdefa#00CF00FF:"Inbound" GPRINT:cdefa:LAST:" Current\:%8.2lf %s" GPRINT:cdefa:AVERAGE:"Avg\:%8.2lf %s"
GPRINT:cdefa:MAX:"Max\:%8.2lf %s\n" COMMENT:"Total In\: 0 bytes\n" LINE1:cdeff#002A97FF:"Outbound"
GPRINT:cdeff:LAST:" Current\:%8.2lf %s" GPRINT:cdeff:AVERAGE:"Avg\:%8.2lf %s" GPRINT:cdeff:MAX:"Max\:%8.2lf %s\n"
COMMENT:"Total Out\: 0 bytes\n" LINE1:cdefba#FF0000FF:"Total In+Out" GPRINT:cdefba:LAST:"Current\:%8.2lf %s"
GPRINT:cdefba:AVERAGE:"Avg\:%8.2lf %s" GPRINT:cdefba:MAX:"Max\:%8.2lf %s\n" COMMENT:"Total In+Out\: 0 bytes\n"
CACTI2RRD: /usr/bin/rrdtool fetch /var/www/html/rra/xyxyxy_relayrouter_traffic_in_7694.rrd AVERAGE -s -300 -e -5 -r 5
CACTI2RRD: /usr/bin/rrdtool info /var/www/html/rra/xyxyxy_relayrouter_traffic_in_7694.rrd
So clearly the cache RRD is not getting created. However, the realtime cache directory is owned by apache.apache (as is the whole cacti directory structure). Just as a "let's see" I turned on +w for the realtime cache directory, but got no change.ERROR: opening '/var/www/html/plugins/realtime/cache/realtime_7694_5.rrd': No such file or directory
Is there some other ownership thing that I'm missing?