#!/bin/bash

# Author: Alan J. Pippin
# Description: This script will attempt to scrub a given USB drive
#              This script ensures that only 1 scrub operation is 
#              running at any given time. This serializes the zfs 
#              scrub process for any pool.

maxsleeptime=360
mailto=root

for i in backups
do
  # Check to see if any zfs filesystem has a scrub being performed on it now.
  # If it does, we cannot perform more than one scrub operation at a time.
  while true; do
    /sbin/zpool status | grep scrub: | grep "in progress" > /dev/null 2>&1
    if [ $? == 0 ]; then
        # Another zpool scrub operation is already running
        # Wait until it is done before continuing
        ransleep=$(($RANDOM % $maxsleeptime))
        sleep $ransleep
    else
        # Another zpool scrub operation is not running
        break
    fi
  done

  echo "Scrubing zfs pool $i"
  /usr/local/etc/bin/usb-drive-power on
  /sbin/zpool import $i
  /sbin/zpool scrub $i

  # Wait until the scrub completes, and check for any errors
  while true; do
    /sbin/zpool status $i | grep scrub: | grep "in progress" > /dev/null 2>&1
    if [ $? == 0 ]; then
        # Our zpool scrub operation is still running
        # Wait until it is done before continuing
        ransleep=$(($RANDOM % $maxsleeptime))
        sleep $ransleep
    else
        # Our scrub operation has completed
        break
    fi
  done

  # Check for any scrub errors
  /sbin/zpool status $i | grep scrub: | grep "with 0 errors" > /dev/null 2>&1
  if [ $? != 0 ]; then
    # The scrub found errors
    /sbin/zpool status $i | /usr/bin/mailx -s "zpool scrub $i found errors" $mailto 
  fi 

  # Power off the USB drive
  /sbin/zpool export $i
  /usr/local/etc/bin/usb-drive-power off

done