Collectd 'exec' plugin is not generating RRD file

I'm trying to collect Wireless statistics from Access Point (AP) device and view the output using Kafka server. I've added 'exec' plugin in OpenWrt code using 'make menuconfig' (Utilities --> collectd --> collectd-mod-exec). After successful build, I flashed firmware image into AP and now I'm able to see exec plugin. I've given a script file to exec plugin as input.

RRD files are created in '/tmp/rrd'. But, my problem here is, RRD file is not generated constantly. I'm restarting luci and collectd process but still having problem in RRD file creation. Sometime I couldn't see RRD file at all in AP. Please support me to generate RRD files constantly using collectd exec plugin with script. Thanks.

Collectd Config file (/etc/collectd.conf)

BaseDir "/var/run/collectd"
Include "/etc/collectd/conf.d"
PIDFile "/var/run/"
PluginDir "/usr/lib/collectd"
TypesDB "/usr/share/collectd/types.db"
Interval 5
ReadThreads 2

LoadPlugin rrdtool
<Plugin rrdtool>
        DataDir "/tmp/rrd"
        RRARows 100
        RRASingle false
        RRATimespan 3600
        RRATimespan 86400
        RRATimespan 604800
        RRATimespan 2678400
        RRATimespan 31622400

LoadPlugin interface
<Plugin interface>
        IgnoreSelected false
        Interface wifi0
        Interface wifi1

LoadPlugin network
<Plugin network>
        Server "" "25826"
        Forward true

LoadPlugin exec
<Plugin exec>
        Exec "nobody:nogroup" "/tmp/rrd/OpenWrt1/"

Script file (/tmp/rrd/OpenWrt1/



INTERVAL=$(awk -v i=$INTERVAL 'BEGIN{print int(i)}')

while sleep $INTERVAL; do
    val=$(dd if=/dev/urandom bs=1 count=1 2>/dev/null |apstats | awk '/Rx PHY errors/ {print $5}')
    echo "PUTVAL \"$HOST/exec-wlanstats/temperature-rx_phy_errors\" interval=$INTERVAL N:$val"

Debugging method followed:
/etc/init.d/luci_statistics restart
/etc/init.d/collectd/ restart

RRD file generated as below:

Please provide sample dataset from exec-script output...

Nobody else can test if you are using custom binaries...