『阿男的代码漫谈时间』＊02＊让我们聊一聊缓存_Ruby_编程开发_程序员俱乐部

class="ruby">
require 'set'

class Generator
    def self.unique_keys(n, max)
        randoms = Set.new
        loop do
            randoms << rand(max)
            return randoms.to_a if randoms.size >= n
        end
    end

    def self.generate_sample_data
        open('data_sample.txt', 'w') { |f|
            unique_keys(100000, 100000).each do |key|
                f.puts "#{key}:#{(0...5).map { ('a'...'z').to_a[rand(26)] }.join}"
            end
        }
    end
end

class Searcher
    def search(target_key)
        File.open('data_sample.txt', 'r') do |f|
            f.each_line do |line|
                entry = line.split(':')
                key = entry[0]
                val = entry[1]
                if key.to_i == target_key
                    puts "#{key}: #{val}"
                    return entry
                end
            end
        end
    end
end

searcher = Searcher.new
(0..500).each do
    searcher.search(rand(10))
end

class Cache
    def initialize
        @repo = Hash.new
        @query_times = 0
        @missed_times = 0
    end

    def read(key)
        @query_times += 1
        if (@repo[key] == nil)
            @missed_times += 1
            return nil
        else
            return @repo[key]
        end
    end

    def write(key, val)
        @repo[key] = val
    end

    def hit_rate
        return (@query_times - @missed_times).to_f / @query_times
    end
end

class CachedSearcher
    def initialize
        @cache = Cache.new
    end

    attr_reader :cache

    def search(target_key)
        if @cache.read(target_key) != nil
            puts "#{target_key}: #{@cache.read(target_key)}"
            return
        else
            File.open('data_sample.txt', 'r') do |f|
                f.each_line do |line|
                    entry = line.split(':')
                    key = entry[0].to_i
                    val = entry[1]
                    if key == target_key
                        @cache.write(key, val)
                        puts "#{key}: #{val}"
                        return entry
                    end
                end
            end
        end
    end
end

# cached_searcher = CachedSearcher.new
# (0..500).each do
#     cached_searcher.search(rand(10))
# end
# puts "cache hit rate: #{cached_searcher.cache.hit_rate}"

• data_sample.txt.zip (673 KB)
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