kvs_client.rb

require 'socket'
100.times.map do |t|
  Thread.new do
    socket = TCPSocket.new 'localhost', 9876
    100.times do
      key = rand 100
      cmd = ["get #{key}", "set #{key} #{t}_#{rand}", "delete #{key}"].sample
      socket.puts cmd
      p [t, cmd, socket.gets]
    end
    socket.close
  end
end.map(&:join)
p TCPSocket.new('localhost', 9876).then{|socket|100.times.map{|i|socket.puts("get #{i}");socket.gets.strip}.tap{socket.close}}

kvs_server.rb

require "socket"
class KVSServer
  def initialize(port)
    @server = TCPServer.new port
    @kvs_ractors = 16.times.map { run_kvs_ractor }
    run_accept_loop
  end

  def run_kvs_ractor
    Ractor.new do
      hash = {}
      loop do
        data = Ractor.recv
        pipe, (cmd, key, value) = data
        case cmd
        when 'get'
          pipe.send hash[key]
        when 'set'
          prev = hash[key]
          hash[key] = value
          pipe.send prev
        when 'delete'
          hash.delete key
          pipe.send :ok
        end
      end
    end
  end

  def run_accept_loop
    loop do
      socket = @server.accept
      serve socket
    end
  end

  def serve(_socket)
    Ractor.new(*@kvs_ractors) do |*kvs|
      socket = Ractor.recv
      ractor_for = -> key { kvs[key.hash % kvs.size] }
      pipe = Ractor.new do
        loop { Ractor.yield Ractor.recv }
      end
      while (line = socket.gets) do
        cmds = line.split(' ')
        case cmds
        in ['get' | 'delete', key]
          ractor_for[key].send [pipe, cmds], move: true
        in ['set', key, String]
          ractor_for[key].send [pipe, cmds], move: true
        else
          socket.puts "valid commands are `get [key]` `set [key] [value]` and `delete [key]`"
          next
        end
        socket.puts pipe.take
      end
    ensure
      socket.close
    end.send _socket, move: true
  end
end

KVSServer.new 9876

kvs_telnet.txt

% telnet localhost 9876
Trying ::1...
Connected to localhost.
Escape character is '^]'.
aaaaaaa
valid commands are `get [key]` `set [key] [value]` and `delete [key]`
get foo

set foo 123

set foo 456
123
get foo
456
delete foo
ok
get foo