#!/bin/bash

file="/var/spool/icinga2/iostat_data.txt"
lockfile="/tmp/iostat_check.lock"
partition="$1"
warning="$2"
critical="$3"
MAX_WAIT=60

start_iostat_collection() {
    touch "$lockfile"
    setsid bash -c "
        stdbuf -oL iostat -d 1 50 -k \
        | awk -v part='^$partition' '\$0 ~ part { if (++count > 1) print }' \
        >> '$file'
        rm -f '$lockfile'
    " >/dev/null 2>&1 &
}

# Validate inputs
if [[ -z "$partition" || -z "$warning" || -z "$critical" ]]; then
	echo "UNKNOWN - Missing arguments. Usage: $0 <partition> <warning_kB/s> <critical_kB/s>"
	exit 3
fi

# Acquire fcntl-style lock using flock
exec 200>"$lockfile"
flock -w $MAX_WAIT 200
if [ $? -ne 0 ]; then
	echo "UNKNOWN - Could not acquire lock on $lockfile after $MAX_WAIT seconds."
	exit 3
fi

# If the data file doesn't exist, this is the first run (e.g. after reboot)
if [ ! -f "$file" ] || { [ ! -s "$file" ] && ! pgrep -f "/usr/bin/iostat" > /dev/null; }; then
	touch "$file"
	start_iostat_collection
	echo "UNKNOWN - Initial iostat data collection in progress. Please wait for the next check."
	exit 3
fi

# If the file is still empty, wait until we have usable data
if [ ! -s "$file" ]; then
	echo "UNKNOWN - No iostat data available yet. Waiting for data to populate."
	exit 3
fi

# Compute averages using awk
read avg_tps avg_read avg_written <<< $(awk '
{
	tps += $2;
	read += $3;
	wrtn += $4;
	count++;
}
END {
	if (count > 0)
		printf "%.2f %.2f %.2f", tps / count, read / count, wrtn / count;
	else
		print "0 0 0"
}' "$file")

PerfData="tps=${avg_tps};;;; KB_read/s=${avg_read};;;; KB_written/s=${avg_written};;;;"

status=0
ret_type="OK"

# Determine status based on thresholds
if (( $(echo "$avg_read >= $critical" | bc -l) )); then
	ret_type="CRITICAL"
	status=2
elif (( $(echo "$avg_read >= $warning" | bc -l) )); then
	ret_type="WARNING"
	status=1
fi

echo "$ret_type - Average I/O: tps=${avg_tps}, read=${avg_read}kB/s, written=${avg_written}kB/s | $PerfData"

# Reset data for next run
cat /dev/null > "$file"
start_iostat_collection

exit $status