namespace :cache do
  CLEAR_BATCH_SIZE = 1000 # There seems to be no speedup when pushing beyond 1,000
  REDIS_SCAN_START_STOP = '0' # Magic value, see http://redis.io/commands/scan

  desc "GitLab | Clear redis cache"
  task :clear => :environment do
    Gitlab::Redis.with do |redis|
      cursor = REDIS_SCAN_START_STOP
      loop do
        cursor, keys = redis.scan(
          cursor,
          match: "#{Gitlab::Redis::CACHE_NAMESPACE}*", 
          count: CLEAR_BATCH_SIZE
        )
  
        redis.del(*keys) if keys.any?
  
        break if cursor == REDIS_SCAN_START_STOP
      end
    end
  end
end