device-mapper-cache-info-to-json.sh

#!/bin/sh

if [ "$#" -eq 0 ] ; then
    cat <<EOF
{
    "data":
    [
        {
$(for a in `dmsetup status | grep -E "^.+: [0-9]+ [0-9]+ cache .+$" | cut -d: -f1`; do echo "            \"{#DEVICE_NAME}\": \"$a\"" ; done)
        }
    ]
}
EOF
    exit 0

elif [ "$#" -ne 1 ] ; then
    echo "Usage: $0 <block-device-or-mapper-name> or $0" >&2
    exit 1
fi

case $1 in
    "/dev/"*) DEVICE=$1 ;;
    *) DEVICE="/dev/mapper/$1" ;;
esac


if [ ! -r "$DEVICE" ] ; then
    echo "$DEVICE could not be read" >&2
    exit 1
fi

if [ ! -b "$DEVICE" ] ; then
    echo "$DEVICE is no block device." >&2
    exit 1
fi

RAW=$(dmsetup status "$DEVICE" 2> /dev/null)
if [ "$?" -ne 0 ] ; then
    echo "$DEVICE could not be analyzed. Try running \"dmsetup status $DEVICE\" to see what's happening." >&2
    exit 1
fi

set -- $RAW

if [ "$3" != "cache" ] ; then
    echo "That is no cache device, but a $DEVICE_TYPE device." >&2
    exit 1
fi

METADATA_BLOCK_SIZE=$4
USED_METADATA_BLOCKS=$(echo "$5" | cut -d/ -f 1)
TOTAL_METADATA_BLOCKS=$(echo "$5" | cut -d/ -f 2)
CACHE_BLOCK_SIZE=$6
USED_CACHE_BLOCKS=$(echo "$7" | cut -d/ -f 1)
TOTAL_CACHE_BLOCKS=$(echo "$7" | cut -d/ -f 2)
READ_HITS=$8
READ_MISSES=$9
WRITE_HITS=${10}
WRITE_MISSES=${11}
DEMOTIONS=${12}
PROMOTIONS=${13}
DIRTY=${14}

cat <<EOF
{
    "metadata_block_size": $METADATA_BLOCK_SIZE,
    "used_metadata_blocks": $USED_METADATA_BLOCKS,
    "total_metadata_blocks": $TOTAL_METADATA_BLOCKS,
    "cache_block_size": $CACHE_BLOCK_SIZE,
    "used_cache_blocks": $USED_CACHE_BLOCKS,
    "total_cache_blocks": $TOTAL_CACHE_BLOCKS,
    "read_hits": $READ_HITS,
    "read_misses": $READ_MISSES,
    "write_hits": $WRITE_HITS,
    "write_misses": $WRITE_MISSES,
    "demotions": $DEMOTIONS,
    "promotions": $PROMOTIONS,
    "dirty": $DIRTY,
    "needs_check": "$(eval echo "\${$#}")"
}
EOF