#!/usr/bin/env bash
#  vim:ts=4:sts=4:sw=4:et
#
#  Author: Hari Sekhon
#  Date: 2019-11-27 16:09:34 +0000 (Wed, 27 Nov 2019)
#
#  https://github.com/harisekhon/bash-tools
#
#  License: see accompanying Hari Sekhon LICENSE file
#
#  If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback
#
#  https://www.linkedin.com/in/harisekhon
#

set -euo pipefail
[ -n "${DEBUG:-}" ] && set -x

usage(){
    cat <<EOF
Recurses HDFS path arguments outputting HDFS MD5-of-MD5 checksums for each file in parallel
since dfs command has slow startup

Calls HDFS command which is assumed to be in \$PATH

Capture stdout | sort > file.txt for comparisons

Make sure to kinit before running this if using a production Kerberized cluster

Setting environment variable SKIP_ZERO_BYTE_FILES to any value will skip files with zero bytes to save time since
they always return the same checksum anyway:

MD5-of-0MD5-of-0CRC32   00000000000000000000000070bc8f4b72a86921468bf8e8441dce5

Caveats:

HDFS command startup is slow and is called once per file so I work around this by launching several dfs commands
in parallel. Configure parallelism via environment variable PARALLELISM=N where N must be an integer

See Also:

hadoop_hdfs_files_native_checksums.jy

from the adjacent GitHub repo:

https://github.com/HariSekhon/DevOps-Python-tools

I would have written this version in Python but the Snakebite library doesn't support checksum extraction


usage: ${0##*/} <file_or_directory_paths>


EOF
    exit 3
}

if [[ "${1:-}" =~ ^- ]]; then
    usage
fi

#PARALLELISM="${PARALELLISM:-$(grep -c '^processor[[:space:]]*:' /proc/cpuinfo)}"
# don't use all cores because if running on a datanode it might have dozens of cores and overwhelm namenode
# cap at 10 unless explicitly set
export PARALLELISM="${PARALLELISM:-10}"

if ! [[ "$PARALLELISM" =~ ^[[:digit:]]+$ ]]; then
    echo "PARALLELISM must be set to an integer!"
    exit 4
fi

skip_zero_byte_files(){
    if [ -n "${SKIP_ZERO_BYTE_FILES:-}" ]; then
        awk '{if($5 != 0) print }'
    else
        cat
    fi
}

hdfs dfs -ls -R "$@" |
grep -v '^d' |
skip_zero_byte_files |
awk '{ $1=$2=$3=$4=$5=$6=$7=""; print }' |
#sed 's/^[[:space:]]*//' |
while read -r filepath; do
    echo "hdfs dfs -checksum '$filepath'"
done |
parallel -j "$PARALLELISM"