`dump` or `restore` Redis keys

redis_keys.rb

#!/usr/bin/env ruby

require "bundler/inline"
require "json"
require "base64"

gemfile do
  source "https://rubygems.org"

  gem "redis", "~> 4.6"
  gem "hiredis", "~> 0.6"
end

class RedisClient
  attr_reader :redis

  def initialize(url)
    @redis = Redis.new(url: url, driver: :hiredis)
  end
end

class KeysDumper < RedisClient
  def dump(path)
    keys = {}

    puts "Dumping Keys"

    redis.scan_each.each_slice(50) do |batch|
      key_futures = {}

      redis.pipelined do |pipeline|
        batch.each do |key|
          key_futures[key] = {
            data: pipeline.dump(key),
            ttl: pipeline.pttl(key)
          }

          print "."
        end
      end

      key_futures.each do |key, futures|
        keys[key] = {
          data_base64: Base64.encode64(futures.fetch(:data).value),
          ttl: parse_ttl(futures.fetch(:ttl).value),
        }
      end
    end

    puts "\nDone!"

    File.open(path, "w") do |file|
      file.write(JSON.pretty_generate(keys))
    end
  end

  private

  def parse_ttl(value)
    case value
    when -2 then raise "Key not found: #{key}"
    when -1 then nil  # No TTL set for key
    else         value
    end
  end
end

class KeysImporter < RedisClient
  def restore(path)
    puts "Restoring Keys"

    JSON.load_file!(path).each_slice(50) do |keys|
      redis.pipelined do |pipeline|
        keys.each do |key, data|
          pipeline.restore(
            key,
            data.fetch("ttl") || 0,
            Base64.decode64(data.fetch("data_base64")),
            replace: true
          )

          print "."
        end
      end
    end

    puts "\nDone!"
  end
end

redis_url       = ENV.fetch("REDIS_URL")
keys_file_path  = ENV.fetch("KEYS_FILE") { "keys.json" }

case (cmd = ARGV[0])
when "dump"    then KeysDumper.new(redis_url).dump(keys_file_path)
when "restore" then KeysImporter.new(redis_url).restore(keys_file_path)
when nil       then raise "Need a command, one of 'dump' or 'restore'."
else                raise "Not a valid command: #{cmd}."
end