#!/bin/bash
#
# vcached: VServer cache daemon
#
# Description: A daemon that periodically preallocates vservers and stores
# them in a cache.  Preallocated vservers from the cache may be then used to 
# instantiate real vservers. Requires that /var/run/vcached.pid does not
# exist on startup. Should start/stop/restart from /etc/init.d.
#
# Based on work by:
# 
# Brent Chun - bnc@intel-research.net
# Tristan Koo - tristan.koo@intel-research.net
# William Wung - wungism@uclink.berkeley.edu
#
# Mark Huang <mlhuang@cs.princeton.edu>
# Copyright (c) 2004  The Trustees of Princeton University (Trustees).
#
# $Id: vcached,v 1.1 2004/07/30 16:46:24 mlh-pl_kernel Exp $
#

# number of images to keep cached
slots=32

# fill the cache periodically
period=$((60 * 15))

# nice adjustment
nice=10

# PID file
pidfile=/var/run/vcached.pid

# log file
logfile=/var/log/vcached.log

# run in foreground
foreground=0

# debug
debug=0

# parse options
while getopts 'fd' OPT ; do
    case "$OPT" in
        f) foreground=1 ;;
        d) debug=1 ;;
    esac
done

# check if we are already running
[ -f $pidfile ] && exit 1

# daemonize
if [ $foreground -eq 0 ] ; then
    nohup nice -n $nice -- $0 $* -f >>$logfile 2>&1 &
    exit 0
fi

# record PID
trap "killall -q -w vbuild ; rm -f $pidfile ; exit 255" EXIT
echo $$ > $pidfile

: ${UTIL_VSERVER_VARS:=$(dirname $0)/util-vserver-vars}
test -e "$UTIL_VSERVER_VARS" || {
    echo "Can not find util-vserver installation; aborting..."
    exit 1
}
. "$UTIL_VSERVER_VARS"

# take out the trash
chattr -R -i "$VROOTDIR/.vtmp"
rm -rf "$VROOTDIR/.vtmp"

mkdir -p "$VROOTDIR/.vcache"
mkdir -p "$VROOTDIR/.vtmp"

# loop forever
while : ; do
    [ $debug -ne 0 ] && echo "$(date) Checking the cache"
    for i in $(seq 0 $(($slots - 1))) ; do
	if [ ! -d "$VROOTDIR/.vcache/v$i" ] ; then
	    echo "$(date) Caching v$i"
	    # build image in .vtmp
	    "$PKGLIBDIR/vbuild" "$VROOTDIR/vserver-reference" "$VROOTDIR/.vtmp/v$i"
	    # move it to .vcache when complete
	    mv "$VROOTDIR/.vtmp/v$i" "$VROOTDIR/.vcache/v$i"
	    echo "$(date) v$i ready"
	fi
    done
    [ $debug -ne 0 ] && echo "$(date) Sleeping for $period seconds"
    sleep $period
done