<repo_name>Vertalo/ec2-scripts<file_sep>/ec2_ephemeralswap
#!/bin/sh

# PROVIDE: ec2_ephemeralswap
# REQUIRE: NETWORKING
# BEFORE: savecore

# Define ec2_ephemeralswap_enable=YES in /etc/rc.conf to enable slicing
# of the ephemeral disks to create swap space when the system next boots.
#
# Define ec2_ephemeralswap_size=N in /etc/rc.conf to use N MB of swap space
# instead of auto-sizing based on the amount of RAM.
#
: ${ec2_ephemeralswap_enable=NO}
: ${ec2_ephemeralswap_size=AUTO}

. /etc/rc.subr

name="ec2_ephemeralswap"
rcvar=ec2_ephemeralswap_enable
start_cmd="ec2_ephemeralswap_run"
stop_cmd=":"

ec2_ephemeralswap_run()
{
	local RAM RAMMB SWAPMB SWZONESTRUCTS SWZONEMAXMB
	local EC2DISKS EC2DISK BLKDEV SWAPDISKS NSWAPDISKS
	local SWAPPERDISK SWAPDISK

	# Compute "ideal" swap size:
	#     2*RAM if RAM <= 4 GB
	#     8 GB  if 4 GB <= RAM <= 8 GB
	#     RAM   if 8 GB <= RAM
	RAM=`sysctl -n hw.physmem`
	RAMMB=`expr $RAM / 1048576`
	if [ $RAMMB -lt 4096 ]; then
		SWAPMB=`expr $RAMMB \* 2`
	elif [ $RAMMB -lt 8192 ]; then
		SWAPMB=8192
	else
		SWAPMB=$RAMMB
	fi

	# If a swap size was specified, use that instead of our "ideal" value.
	case ${ec2_ephemeralswap_size} in
	[Aa][Uu][Tt][Oo])
		;;
	*)
		SWAPMB=${ec2_ephemeralswap_size}
		;;
	esac

	# Reduce this size if the kernel hasn't reserved enough space to
	# keep track of that much swap.
	SWZONESTRUCTS=`vmstat -z | tr -d , | awk '/^SWAPMETA/ { print $3 }'`
	SWZONEMAXMB=`expr $SWZONESTRUCTS / 16`
	if [ $SWZONEMAXMB -lt $SWAPMB ]; then
		echo -n "Reducing ephemeral swap target from $SWAPMB MB to"
		echo -n " $SWZONEMAXMB MB since kernel SWAPMETA zone is"
		echo " too small."
		SWAPMB=$SWZONEMAXMB
	fi

	# Fetch a list of EC2 disks
	EC2DISKS=`fetch -qo - http://169.254.169.254/latest/meta-data/block-device-mapping/ | grep -E '^ephemeral[0-9]+$'`
	debug "EC2 ephemeral disks are $EC2DISKS"

	# Figure out where they're mapped to
	SWAPDISKS=""
	NSWAPDISKS=0
	for EC2DISK in $EC2DISKS; do
		BLKDEV=`fetch -qo - http://169.254.169.254/latest/meta-data/block-device-mapping/$EC2DISK | sed 's|/dev/||'`
		case "$BLKDEV" in
		sd[a-j])
			SWAPDISK="/dev/xbd`echo $BLKDEV | cut -c 3 | tr 'a-j' '0-9'`"
			;;
		xvd[a-z])
			SWAPDISK="/dev/xbd`echo $BLKDEV | cut -c 4 | tr 'a-j' '0-9'`"
			;;
		*)
			echo "Can't translate $EC2DISK to a FreeBSD device name"
			continue
			;;
		esac
		if [ -c $SWAPDISK ]; then
			SWAPDISKS="$SWAPDISKS $SWAPDISK"
			NSWAPDISKS=$(($NSWAPDISKS + 1))
		else
			debug "Ephemeral swap disk $SWAPDISK doesn't exist"
		fi
	done

	# If we have no ephemeral disks, give up.
	if [ $NSWAPDISKS -eq 0 ]; then
		echo -n "No ephemeral disks are available,"
		echo " so no swap space is being created."
		return 0;
	fi

	# How much swap space do we want per disk?
	SWAPPERDISK=`expr $SWAPMB / $NSWAPDISKS`
	if [ $SWAPPERDISK -gt 32768 ]; then
		# FreeBSD swap_pager code can't use more than 32 GB per device
		SWAPPERDISK=32768
	fi

	debug "Want $SWAPPERDISK MB swap on each of $NSWAPDISKS disks: $SWAPDISKS"

	# Slice and partition disks
	for SWAPDISK in $SWAPDISKS; do
		if [ `ls $SWAPDISK[a-z.]* 2>/dev/null | wc -l` -gt 1 ]; then
			debug "Ephemeral swap disk $SWAPDISK already in use"
			continue;
		fi

		# Figure out how large the disk is.  Subtract off 16 MB for
		# losses to "cylinder" alignment etc.
		DISKSZ=`diskinfo $SWAPDISK | awk '{ print $3 }'`
		DISKSZM=`expr $DISKSZ / 1048576 - 16`

		# Use the size we want or the size we've got, whichever is less
		if [ $DISKSZM -lt $SWAPPERDISK ]; then
			SWAPSZ=$DISKSZM;
		else
			SWAPSZ=$SWAPPERDISK;
		fi

		# Try to create a $SWAPSZ MB slice on this disk.
		echo -n "Attempting to create a $SWAPSZ MB swap area on $SWAPDISK..."
		( echo "p 1 0xa5 64 ${SWAPSZ}M"; echo "p 2 0xa5 * *" ) |
		    fdisk -i -f /dev/stdin $SWAPDISK >/dev/null 2>/dev/null

		# Attempt to create a swap partition on the new slice.
		( echo "b: * 0 swap"; echo "c: * 0 unused" ) |
		    bsdlabel -R ${SWAPDISK}s1 /dev/stdin

		# Did we succeed?
		if [ -c ${SWAPDISK}s1b ]; then
			echo " done."
		else
			echo " failed."
		fi
	done

	# Turn on swap
	for SWAPDISK in $SWAPDISKS; do
		# If there isn't an s1b partition, this isn't one of ours.
		if ! [ -c "${SWAPDISK}s1b" ]; then
			continue;
		fi

		# Make sure that s1b is a swap partition.
		if ! bsdlabel ${SWAPDISK}s1 | grep b: | grep -q swap; then
			continue;
		fi

		# Enable swap on this disk
		echo "Enabling swapping to ${SWAPDISK}s1b"
		swapon ${SWAPDISK}s1b
	done

	# Turn on dumping, if ${dumpdev} is AUTO (the dumpon rc.d script runs
	# early in the boot process, but we can't run until the network has
	# been brought up -- so we duplicate here some of the work which that
	# script does.
	case ${dumpdev} in
	[Aa][Uu][Tt][Oo])
		for SWAPDISK in $SWAPDISKS; do
			# Skip if this is not a disk we're swapping to.
			if ! swapinfo | grep -Eq "^${SWAPDISK}s1b"; then
				continue;
			fi

			# If we don't have a dump disk yet, use this one.
			if ! [ -e /dev/dumpdev ]; then
				echo "Enabling crash dumps to ${SWAPDISK}s1b"
				dumpon ${SWAPDISK}s1b
				ln -sf ${SWAPDISK}s1b /dev/dumpdev
			fi
		done
		;;
	esac
}

load_rc_config $name
run_rc_command "$1"
