#!/bin/sh


# Little custom script to :
# - check if the system has a heavy swap activity
# - record swapin activity as perfdata
#
# For pnp4nagios' sake, create a file usually named 'check_nrpe_swaping.cfg'
# (depends on your configuration) with the following content :
#  DATATYPE = COUNTER,COUNTER


# Default values
THRESHOLD_WARNING="50"
THRESHOLD_CRITICAL="200"
VMSTAT_PREVIOUS_DATA_FILE="/tmp/.monitoring_vmstat.txt"


# Output
OUTPUT_EXIT_STATUS=0
OUTPUT_DETAIL_WARNING=""
OUTPUT_DETAIL_CRITICAL=""
OUTPUT_PERFDATA=""

PROGPATH=$( echo $0 | sed -e 's,[\\/][^\\/][^\\/]*$,,' )
REVISION="0.1"

# Stop at the first non-catched error
set -e

# Include check_range()
. $PROGPATH/utils.sh
# If you don't have the previous file, just comment the line and uncomment the following
# (it's only possible because we don't use the range checking function in this script)
#STATE_OK=0
#STATE_WARNING=1
#STATE_CRITICAL=2
#STATE_UNKNOWN=3
#STATE_DEPENDENT=4


#
# Help function
#
usage() {
	cat <<EOF
Usage :
  $0 [-w warning_threshold] [-c critical_threshold] [-f vmstat_previous_data_file ]

Note 1 : the script will measure the number of seconds passed since its last call and will
         divide the measures accordingly, so write the thresholds using pages/s in mind.
         The script will measure against pswpin and pswpout added together.

Note 2 : the thresholds use the kernel page size as unit. Use 'getconf PAGESIZE' to get it if needed.

Default values:
  warning_threshold         : $THRESHOLD_WARNING
  critical_threshold        : $THRESHOLD_CRITICAL
  vmstat_previous_data_file : $VMSTAT_PREVIOUS_DATA_FILE
EOF
}

#
# Copy fresh vmstat data into the file passed as an argument
#
update_vmstat_previous_data_file() {
	# Harden default files permissions to avoid some data leaks
	umask "0077" || true

	echo "# This file was written by $0 for monitoring swap activity." >"$1"
	echo "# It can be deleted if the need arise, it will be easily recreated without too much lost." >>"$1"
	echo "" >>"$1"

	cat /proc/vmstat >> "$1"
}

#
# Check if arg is an integer
# (copied from jilles @ http://stackoverflow.com/questions/806906/how-do-i-test-if-a-variable-is-a-number-in-bash )
#
is_int() {
	case "$1" in
		''|*[!0-9]*) return 1;;
		*) return 0;;
	esac
}


#
# Parameters management
#
while getopts hw:c:f: f; do
	case "$f" in
		'h')
			usage
			exit
			;;

		'w')
			THRESHOLD_WARNING="$OPTARG"
			;;

		'c')
			THRESHOLD_CRITICAL="$OPTARG"
			;;

		'f')
			VMSTAT_PREVIOUS_DATA_FILE="$OPTARG"
			;;

		\?)
			usage
			exit 1
			;;
	esac
done
shift $( expr $OPTIND - 1 )

# Little checks
if ! is_int "$THRESHOLD_WARNING" || ! is_int "$THRESHOLD_CRITICAL"; then
	echo "UNKNOWN invalid parameter : one of the threshold is not an integer."
	exit $STATE_UNKNOWN
fi

# Check if the previous data file exists
if [ ! -w "$VMSTAT_PREVIOUS_DATA_FILE" ]; then
	update_vmstat_previous_data_file "$VMSTAT_PREVIOUS_DATA_FILE"

	# We wait a little bit to gather some data even on the first run
	# (or we could return an UNKNOWN ?)
	sleep 2
fi

# Read previous data
PREVIOUS_PSWPIN="$( grep '^pswpin' "$VMSTAT_PREVIOUS_DATA_FILE" | cut -d " " -f 2 )"
PREVIOUS_PSWPOUT="$( grep '^pswpout' "$VMSTAT_PREVIOUS_DATA_FILE" | cut -d " " -f 2 )"
PREVIOUS_PSWPTOTAL=$(( $PREVIOUS_PSWPIN + $PREVIOUS_PSWPOUT ))

# Get time elapsed since last call
PREVIOUS_DATA_AGE=$(( $( date +%s ) - $( stat --printf="%Y" "$VMSTAT_PREVIOUS_DATA_FILE" ) ))
if [ "$PREVIOUS_DATA_AGE" -le "0" ]; then
	echo "UNKNOWN: $PREVIOUS_DATA_AGE second(s) elapsed since last call."
	exit $STATE_UNKNOWN
fi

# Update and read current data
update_vmstat_previous_data_file "$VMSTAT_PREVIOUS_DATA_FILE"
CURRENT_PSWPIN="$( grep '^pswpin' "$VMSTAT_PREVIOUS_DATA_FILE" | cut -d " " -f 2 )"
CURRENT_PSWPOUT="$( grep '^pswpout' "$VMSTAT_PREVIOUS_DATA_FILE" | cut -d " " -f 2 )"
CURRENT_PSWPTOTAL=$(( $CURRENT_PSWPIN + $CURRENT_PSWPOUT ))

# Calculate the swaping rate
PSWP_RATE=$(( ( $CURRENT_PSWPTOTAL - $PREVIOUS_PSWPTOTAL ) / $PREVIOUS_DATA_AGE ))

# Generate perfdata
OUTPUT_PERFDATA="$( printf " pswpin=%d pswpout=%d" "$CURRENT_PSWPIN" "$CURRENT_PSWPOUT" )"

# Comparison
# note: remember that numbers can be reseted to zero from time to time (64bits counter ?)
if [ $PSWP_RATE -gt $THRESHOLD_CRITICAL ]; then
	echo "CRITICAL swaping rate at $PSWP_RATE (limit at $THRESHOLD_CRITICAL) |$OUTPUT_PERFDATA"
	exit $STATE_CRITICAL
elif [ $PSWP_RATE -gt $THRESHOLD_WARNING ]; then
	echo "WARNING swaping rate at $PSWP_RATE (limit at $THRESHOLD_WARNING) |$OUTPUT_PERFDATA"
	exit $STATE_WARNING
fi

echo "OK swaping rate at $PSWP_RATE |$OUTPUT_PERFDATA"
exit $STATE_OK