#!/bin/bash
# Postfix queue depth textfile metric — runs every 5 min via root crontab.

TEXTFILE="/var/lib/node_exporter/textfile/postfix_queue.prom"
HOSTNAME=$(hostname -s)
TMPFILE=$(mktemp /tmp/postfix_queue.XXXXXX.prom)
trap 'rm -f "$TMPFILE"' EXIT

QUEUE_SIZE=0
if command -v mailq >/dev/null 2>&1; then
    # grep -c exits 1 on no match even for count=0; handle separately
    QUEUE_SIZE=$(mailq 2>/dev/null | grep -c '^[0-9A-F]' 2>/dev/null) || QUEUE_SIZE=0
fi

cat > "$TMPFILE" << EOF
# HELP postfix_queue_size Number of messages in postfix mail queue
# TYPE postfix_queue_size gauge
postfix_queue_size{host="${HOSTNAME}"} ${QUEUE_SIZE}
# HELP postfix_queue_check_last_run_seconds Unix timestamp of last queue check
# TYPE postfix_queue_check_last_run_seconds gauge
postfix_queue_check_last_run_seconds $(date +%s)
EOF

mkdir -p "$(dirname "$TEXTFILE")"
mv "$TMPFILE" "$TEXTFILE"
chmod 644 "$TEXTFILE"
trap - EXIT
exit 0