spaceblog

Ok, this might be the last one ;-)

As mentioned previously, I've been writing a script that net-snmp can pass off the UCD-DISKIO-MIB requests to, for those versions that don't have it built in, and to save one from rebuilding net-snmp packages.

This time around, I've added support for 2.4 series kernels, which use /proc/partitions instead of /proc/diskstats to log the disk IO stats.

I've now got this running in production across a handful of machines, and it's pretty neat -- I am able to see the shape of disk traffic during a vacuum on one of our machines, alongside the CPU and memory usage, and load average graphs, for example.

As before, plop it into /usr/local/sbin/snmp-diskio-collector and add this line to your snmpd.conf:

pass .1.3.6.1.4.1.2021.13.15 /usr/local/sbin/snmp-diskio-collector

Here's the script:

#!/bin/sh

# by Jamie Wilkinson <jamie@anchor.net.au>
# this code is in the public domain
# based on passtest from the net-snmp distribution examples
# WARNING there is shitloads of IO required to get this information :)

debug_flag=0

debug () {
    if [ $debug_flag -eq 1 ]; then
        echo $* >> /tmp/snmp-diskio-collector-debug.log
    fi
}

PLACE=".1.3.6.1.4.1.2021.13.15"
REQ="$2"

debug
debug "new run" 
debug "args $*" 
if [ "$1" = "-s" ]; then
  exit 0
fi

# the 'tail' of the oid, everything after $PLACE
oidtail=`echo $REQ | sed "s/^$PLACE//"`
debug "oidtail=$oidtail" 

# number of devices we can export
if [ -f /proc/diskstats ]; then
    devcount=`wc -l /proc/diskstats | sed 's/^ *//' | cut -f1 -d' '`
else
    devcount=`wc -l /proc/partitions | sed 's/^ *//' | cut -f1 -d' '`
    devcount=`expr $devcount - 2`
fi
debug "devcount=$devcount" 

item=`echo $oidtail | cut -f4 -d.`
index=`echo $oidtail | cut -f5 -d.`
debug "oidtail=$oidtail, item=$item, index=$index" 

if [ "$1" = "-n" ]; then
    if [ -z "$item" ]; then
        item=1
        index=1
    elif [ -z "$index" ]; then
        index=1
    else
        index=`expr $index + 1`
        if [ "$index" -gt "$devcount" ]; then
            index=1
            item=`expr $item + 1`
            if [ "$item" -gt 6 ]; then
                # break out of the loop
                exit 0;
            fi
        fi
    fi
    RET=$PLACE.1.1.$item.$index
else
    case "$REQ" in
        $PLACE) exit 0;;
        *) RET=$REQ ;;
    esac
fi

debug "after -n, item=$item, index=$index" 
debug "RET is now $RET" 

echo "$RET"

debug "oidtail=$oidtail, item=$item, index=$index" 

# awk uses this variable in the environment below
export index
# see linux kernel Documentation/iostats.txt for format
if [ -n "$index" ]; then
    case "$item" in
        1)
            # diskIOIndex
            debug "result: diskIOIndex $index" 
            echo "integer"
            echo $index
            exit 0
            ;;
        2)
            # diskIODevice
            debug "result: diskIODevice $index" 
            echo "string"
        if [ -f /proc/diskstats ]; then
        awk 'FNR == ENVIRON["index"] { print $3 }' /proc/diskstats
        else
        awk 'FNR == ENVIRON["index"] + 2 { print $4 }' /proc/partitions
        fi
            exit 0
            ;;
        3)
            # diskIONRead
            debug "result: diskIONRead $index" 
            echo "counter"
        if [ -f /proc/diskstats ]; then
        awk 'FNR == ENVIRON["index"] { print $6 }' /proc/diskstats
        else
        awk 'FNR == ENVIRON["index"] + 2 { print $7 }' /proc/partitions
        fi
            exit 0
            ;;
        4)
            # diskIONWritten
            debug "result: diskIONWritten $index" 
            echo "counter"
        if [ -f /proc/diskstats ]; then
        awk 'FNR == ENVIRON["index"] { print $10 }' /proc/diskstats
        else
        awk 'FNR == ENVIRON["index"] + 2 { print $11 }' /proc/partitions
        fi
            exit 0
            ;;
        5)
            # diskIOReads
            debug "result: diskIOReads $index" 
            echo "counter"
        if [ -f /proc/diskstats ]; then
        awk 'FNR == ENVIRON["index"] { print $4 }' /proc/diskstats
        else
        awk 'FNR == ENVIRON["index"] + 2 { print $5 }' /proc/partitions
        fi
            exit 0
            ;;
        6)
            # diskIOWrites
            debug "result: diskIOWrites $index" 
            echo "counter"
        if [ -f /proc/diskstats ]; then
        awk 'FNR == ENVIRON["index"] { print $8 }' /proc/diskstats
        else
        awk 'FNR == ENVIRON["index"] + 2 { print $9 }' /proc/partitions
        fi
            exit 0
            ;;
        *) exit 0; #echo "string"; echo "debug... $RET $REQ"; exit 0 ;;
    esac
else
    exit 0
fi