Redis Migration script

migrate-redis.sh

#!/bin/bash

REDIS_CLI_PREFIX="redis-cli"
DEFAULT_PORT=6379
DEFAULT_DB=0


log () { echo "[$(date +%Y-%m-%dT%H:%M:%S:%:z)] $@" >&2; }

usage () {
    echo -e ">>> RedisMigration:
    Run redis migration from source server to destination.

    Usage: $0 SOURCE           DESTINATION
           $0 host[:port][:db] host[:port][:db]
           $0 0.0.0.0          127.0.0.1
           $0 0.0.0.0:$DEFAULT_PORT     127.0.0.1:$DEFAULT_PORT
           $0 0.0.0.0:$DEFAULT_PORT:$DEFAULT_DB   127.0.0.1:$DEFAULT_PORT:$DEFAULT_DB

    Options:
        -h, --help\tPrint usage

@author Felipe Francisco <[email protected]>
@credits https://elliotchance.medium.com/migrating-data-between-redis-servers-without-downtime-429e4c8048e6
"
    exit 1
}

create_redis_cli () {
    host="$(echo $1 | cut -d: -f1)"
    port="$(echo $1 | cut -d: -f2)"
    db="$(  echo $1 | cut -d: -f3)"

    if [ -z "$port" ] || [ "$port" = "$host" ]; then
        port=$DEFAULT_PORT
    fi

    if [ -z "$db" ] || [ "$db" = "$host" ]; then
        db=$DEFAULT_DB
    fi

    if [ -z "$host" ]; then
        log ERROR "Host cannot be empty"
        exit 2
    fi

    echo "$REDIS_CLI_PREFIX -h $host -p $port -n $db"
}

redis_ping () {
    log INFO "ping redis server: \$($@ ping)"

    $@ ping
    return_exit=$?

    if [ "$return_exit" != 0 ]; then
        log ERROR "\$($@ ping) Exited with $return_exit"
        exit 3
    fi

    log DEBUG "\$($@ ping): connected!"
}


### Main:
# HELP check
if [ -z "$1" ] || [ -z "$2" ] \
    || [ "$1" = "-h" ] || [ "$1" = "--help" ];
then
    usage
fi

OLD_REDIS_CLI="$(create_redis_cli $1)"
NEW_REDIS_CLI="$(create_redis_cli $2)"

redis_ping $OLD_REDIS_CLI
redis_ping $NEW_REDIS_CLI

log "Redis Migration: START..."

DUMP_FILE="/tmp/redis_${1//:/-}.dump"

for KEY in $($OLD_REDIS_CLI --scan); do
    $OLD_REDIS_CLI --raw DUMP "$KEY" | head -c-1 > $DUMP_FILE
    TTL=$($OLD_REDIS_CLI --raw TTL "$KEY")

    case $TTL in
        -2)
            $NEW_REDIS_CLI DEL "$KEY"
            ;;
        -1)
            $NEW_REDIS_CLI DEL "$KEY"
            cat $DUMP_FILE | $NEW_REDIS_CLI -x RESTORE "$KEY" 0
            ;;
        *)
            $NEW_REDIS_CLI DEL "$KEY"
            cat $DUMP_FILE | $NEW_REDIS_CLI -x RESTORE "$KEY" "$TTL"
            ;;
    esac

    log "$KEY (TTL = $TTL)"
done

log "Redis Migration: DONE!"

exit 0

to run over databases at once:

#!/bin/bash

for n in $(seq 0 10); do
    ./migrate-redis.sh $1:$n $2:$n &
done

./script first-redis:6379 second-redis:6379