#!/usr/bin/env bash
# KNELPerf iotop snapshot — periodic batch samples of active per-process I/O.
# Complements sar (system-wide device stats) with the WHO behind the I/O.
# Env (or /etc/knelperf/perfsnap.conf):
#   KNELPERF_IOTOP_LOGDIR   default /var/log/knelperf-iotop
# Output: daily file iotop-YYYYMMDD.log; per tick one header line then
#   3 batch iterations x 2s of processes with outstanding I/O (-botqq -k).
# Docs: https://community.turnsys.com/t/328
set -u
CONF=/etc/knelperf/perfsnap.conf
[ -r "$CONF" ] && . "$CONF"
LOGDIR=${KNELPERF_IOTOP_LOGDIR:-/var/log/knelperf-iotop}
mkdir -p "$LOGDIR"
F="$LOGDIR/iotop-$(date +%Y%m%d).log"
{
  echo "### $(date -Iseconds)"
  iotop -botqq -k -n 3 -d 2 2>/dev/null
} >> "$F"
# retention: 14 days; rotate the live file at 25MB
find "$LOGDIR" -name 'iotop-*.log*' -mtime +14 -delete 2>/dev/null
[ "$(wc -c <"$F" 2>/dev/null || echo 0)" -gt 26214400 ] && mv "$F" "$F.1"
exit 0