zpool_iostat

#!/bin/sh
# -*- sh -*-

set -eu

: <<=cut

=head1 NAME

zpool_iostat - Plugin to monitor transfer statistics of ZFS pools

=head1 APPLICABLE SYSTEMS

All systems with "zpool" installed.

=head1 CONFIGURATION

No configuration is required.

=head1 INTERPRETATION

This plugin shows a graph with read (positive) and write (negative) values
for the IO transfer of each pool.

=head1 MAGIC MARKERS

  #%# family=auto
  #%# capabilities=autoconf

=head1 AUTHOR

tsaavik <github@hellspark.com>
Peter Doherty <peterd@acranox.org>
Lars Kruse <devel@sumpfralle.de>

=head1 LICENSE

GPLv2

=cut


# shellcheck source=/usr/share/munin/plugins/plugin.sh
. "$MUNIN_LIBDIR/plugins/plugin.sh"


ZPOOL_BIN=/sbin/zpool
ACTION="${1:-}"


if [ "$ACTION" = "autoconf" ]; then
	if [ -x "$ZPOOL_BIN" ]; then
		echo yes
	else
		echo "no (missing executable '$ZPOOL_BIN')"
	fi
	exit 0
fi

zlines=$("$ZPOOL_BIN" iostat -v | wc -l | sed 's/ //g')
iostats=$("$ZPOOL_BIN" iostat -v 1 1 | tail "-$zlines")
zlist=$(echo "$iostats" \
	| awk '/alloc/ {next}; /avail/ {next}; /raid/ {next}; /mirror/ {next};
		{ if ( $4 >=0 ) print $1}' \
	| tr ' ' '\n')

# Parse the n'th column of the iostat output for a given pool or disk as a
# number (interpreting K and M suffixes).
get_device_iostat_column() {
	local device_label="$1"
	local stat_column="$2"
	# convert all numeric values into kB
	echo "$iostats" \
		| awk '{ if ($1 == "'"$device_label"'") print $'"$stat_column"'; }' \
		| awk '/M/ {print int($1)*1000};
			/K/ {print int($1)};
			/[0-9]$/ {print int($1)/1000}'
}


get_device_fieldname() {
	local device_id="$1"
	# Backwards compatibility (until 2016): keep the unprefixed pool name
	# for the fieldname, except for pool names starting with digits.
	if echo "$device_id" | grep -q "^[0-9]"; then
		clean_fieldname "_$device_id"
	else
		clean_fieldname "$device_id"
	fi
}


if [ "$ACTION" = "config" ]; then
	echo 'graph_title zpool iostat'
	echo 'graph_args --base 1000 -l 0'
	echo 'graph_vlabel write (-) / read (+) KBytes/s'
	echo 'graph_category disk'
	echo 'graph_scale no'
	echo 'graph_info This graph shows zpool iostat'
	# Assemble the "graph_order" as a sorted list of read/write pairs for
	# each device.
	printf "graph_order"
	echo "$zlist" | while read -r device_id; do
		fieldname="$(get_device_fieldname "$device_id")"
		printf " %s_read %s_write" "$fieldname" "$fieldname"
	done
	# finalize the 'graph_order' with a newline
	echo
	# output all fields: write as negative numbers and read as positive
	echo "$zlist" | while read -r device_id; do
		fieldname="$(get_device_fieldname "$device_id")"
		echo "${fieldname}_read.label $device_id"
		echo "${fieldname}_read.type GAUGE"
		echo "${fieldname}_read.graph no"
		echo "${fieldname}_write.label $device_id"
		echo "${fieldname}_write.type GAUGE"
		echo "${fieldname}_write.negative ${fieldname}_read"
	done
	exit 0
fi


echo "$zlist" | while read -r device_id; do
	fieldname="$(get_device_fieldname "$device_id")"
	echo "${fieldname}_read.value $(get_device_iostat_column "$device_id" 6)"
	echo "${fieldname}_write.value $(get_device_iostat_column "$device_id" 7)"
done