To run the command with the root permission, we must create this script first, which will collect the data and write the data to /tmp folder.

mkdir /etc/wg

#!/bin/sh

output=/tmp/wg.collect
rm -f $output && touch $output && chmod 666 $output

current=$(date +%s)

conf="cgCozSFbCG6SvENpITD5n6SF9vWyYO0J6jOuziy3tyU= wg0
wFyXEweIGqzB3Keg/bBmxGfBcKpp222/YMyNwvjRgiQ= wg1"

wg show all latest-handshakes | while read line; do
        device=$(echo $line | awk -F ' ' '{print $1}')
        peer=$(echo $line | awk -F ' ' '{print $2}')
        dt=$(echo $line | awk -F ' ' '{print $3}')
        name=$(echo "$conf" | grep "$peer" | awk -F ' ' '{print $2}')

        if [ "$dt" = "0" ] || [ -z "$name" ]; then
                continue
        fi

        diff=$(($current - $dt))

        echo "PUTVAL \"HOSTNAME/exec-wireguard/gauge-last_handshake_$name\" interval=INTERVAL N:$diff" >> $output
done

The script will write the outputs to the /tmp/wg.collect file. You may want to change the conf settings. It will help us filter which peer we want to monitor and the alias for that peer.

The output is defined here "PUTVAL \"HOSTNAME/exec-wireguard/gauge-last_handshake_$name\" interval=INTERVAL N:$diff". The output format is critical.

• First of all, the HOSTNAME and INTERVAL are placeholders. They will be replaced with the correct value later.
• For the exec-wireguard, exec is the plugin name, the wireguard is the plugin instance name.
• For the gauge-last_handshake_$name, gauge is the metric type. It must be inclued in the /usr/share/collectd/types.db file. You also can use one of the existed type from there. last_handshake_$name is the metric name.

Add the script to the system -> Scheduled Tasks. * * * * * /etc/wg/wg.sh.

Check whether the file /tmp/wg.collect has been created and updated after adding it to the crontab.

Create a file /etc/wg/exec-wg.sh

#!/bin/sh

HOSTNAME="${COLLECTD_HOSTNAME:-Tux}"
INTERVAL="${COLLECTD_INTERVAL:-60}"
INTERVAL=$(awk -v i=$INTERVAL 'BEGIN{print int(i)}')

input=/tmp/wg.collect

while sleep "$INTERVAL"; do
        cat $input | sed "s/HOSTNAME/$HOSTNAME/g" | sed "s/INTERVAL/$INTERVAL/g"
done

This script will run and loop forever, read and print the file content. There is nothing special here.

After adding the file to the exec plugin settings UI, run these commands to check if it works.

# ps |grep exec-wg
 4001 nobody    1088 SN   /bin/sh /etc/wg/exec-wg.sh

# ls <path-to-rrd-data-directory>/exec-wireguard/
gauge-last_handshake_wg0.rrd  gauge-last_handshake_wg1.rrd

Create the file /www/luci-static/resources/statistics/rrdtool/definitions/exec.js as bellow.

'use strict';
'require baseclass';
return baseclass.extend({
    title: _('Exec'),
    rrdargs: function(graph, host, plugin, plugin_instance, dtype) {
        // host: Tux
        // plugin: exec
        // plugin_instance: wireguard
        // dtype: null
        var wireguard_last_handshake_time = {
            title: "%H: wireguard last handshake time",
            vlabel: "seconds",
            alt_autoscale_max: true,
            data: {
                types: ["gauge"],
                options: {
                    gauge_last_handshake_wg0: {
                        color: "ff0000",
                        // noavg: true,
                        noarea: true,
                        // overlay: true,
                        // flip: true,
                        title: "wg0"
                    },
                    gauge_last_handshake_wg1: {
                        color: "0000ff",
                        // noavg: true,
                        noarea: true,
                        title: "wg1"
                    }
                }
            }
        };
        return wireguard_last_handshake_time;
    }
});

The important thing in the file

• title: _('Exec'),: define the graph title.
• types: ["gauge"],: define the source data type.
• gauge_last_handshake_wg0 and gauge_last_handshake_wg1: this is optional. I want to rename the metrics name and set the color for the graph. Please notice the _ after the gauge is very important. Don't use - here.