• ​server.properties - Minecraft Wiki
• ​Minecraft Japan Wiki - マルチプレイ

• server.properties
  • デフォルトからの変更点
    • difficulty=2
      • 難易度:ノーマル
    • snooper-enabled=false
      • true:snoop.minecraft.netにsnoopingデータを送信しない
  • spawn-protection

    ... Setting this to 0 will not disable spawn protection. 0 will protect the single block at the spawn point. ... If there are no ops set on the server, the spawn protection will be disabled automatically.

Can't keep up! Did the system time change, or is the server overloaded?

• CPU負荷が高いと起こる模様
  • latest.log

    [08:00:06] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2056ms behind, skipping 41 tick(s)
    [08:00:24] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 4273ms behind, skipping 85 tick(s)
    [08:00:43] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 5118ms behind, skipping 102 tick(s)
    [08:05:30] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2332ms behind, skipping 46 tick(s)
    [08:05:49] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 5608ms behind, skipping 112 tick(s)
    [08:10:30] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2998ms behind, skipping 59 tick(s)
    [08:10:46] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 3696ms behind, skipping 73 tick(s)
    [08:15:32] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2093ms behind, skipping 41 tick(s)
    [08:15:54] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 4513ms behind, skipping 90 tick(s)
    

• 5分ごとに起きているので、muninによる影響が考えられる
• ​トピック - マルチサーバーの使用メモリの増やし方について • Minecraft 非公式日本ユーザーフォーラム
  • diskI/O軽減のため、 /run/shm/ 上にworldデータを移動しても状況は変わらず

convert single player world data to multi server

1. server.properties のlevel-nameに指定されているフォルダ名(デフォルではworld)に、saves以下のワールドデータをコピー
2. /playerdata/<uuid>.dat を、/players/<player>.dat にコピー /players/<player>.datが存在していれば削除
   • これをしないと出現位置やインベントリの中身などが引き継がれない 古い形式である/players/*.dat ファイルが存在しているとそちらが優先して読み込まれるため

• 参考：​Level format - Minecraft Wiki

sessionserver.mojang.com

• クライアントのサーバーへのログイン時に認証される
  

snoop.minecraft.net

• server.propertiesでsnooper-enabled=true(デフォルト)の時900秒おきに情報が送信される
• ​http://wiki.vg/Snoop

• 起動後一回目の送信

  POST /server?version=2 HTTP/1.1
  Content-Type: application/x-www-form-urlencoded
  Content-Language: en-US
  Cache-Control: no-cache
  Pragma: no-cache
  User-Agent: Java/1.8.0_92
  Host: snoop.minecraft.net
  Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
  Connection: keep-alive
  Content-Length: 301
  
  dedicated=true&gui_supported=headless&os_version=4.5.4-1-ARCH&version=1.9.4&singleplayer=false&jvm_arg%5B1%5D=-Xmx2048M&snooper_token=91b338ef-cec9-4dcb-b01e-0034393c449f&jvm_arg%5B0%5D=-Xms1024M&server_brand=vanilla&snooper_count=0&java_version=1.8.0_92&os_name=Linux&os_architecture=amd64&jvm_args=2
  

  HTTP/1.1 200 OK
  Date: Fri, 20 May 2016 10:53:15 GMT
  Content-Length: 0
  Connection: keep-alive
  

• 2回目以降

  POST /server?version=2 HTTP/1.1
  Content-Type: application/x-www-form-urlencoded
  Content-Language: en-US
  Cache-Control: no-cache
  Pragma: no-cache
  User-Agent: Java/1.8.0_92
  Host: snoop.minecraft.net
  Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
  Connection: keep-alive
  Content-Length: 1122
  
  world%5B2%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bchunks_loaded%5D=0&world%5B0%5D%5Bdifficulty%5D=EASY&players_seen=1&world%5B0%5D%5Bgenerator_version%5D=1&world%5B2%5D%5Bdifficulty%5D=EASY&worlds=3&world%5B1%5D%5Bdifficulty%5D=EASY&world%5B0%5D%5Bmode%5D=SURVIVAL&world%5B1%5D%5Bmode%5D=SURVIVAL&gui_state=disabled&world%5B2%5D%5Bhardcore%5D=false&world%5B1%5D%5Bheight%5D=256&world%5B2%5D%5Bheight%5D=256&whitelist_count=0&world%5B1%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bmode%5D=SURVIVAL&snooper_token=91b338ef-cec9-4dcb-b01e-0034393c449f&whitelist_enabled=false&jvm_arg%5B0%5D=-Xms1024M&snooper_count=2&players_max=20&uses_auth=true&world%5B2%5D%5Bdimension%5D=1&world%5B1%5D%5Bdimension%5D=-1&world%5B1%5D%5Bchunks_loaded%5D=0&world%5B0%5D%5Bdimension%5D=0&world%5B0%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bgenerator_version%5D=1&world%5B0%5D%5Bheight%5D=256&run_time=30022000&avg_tick_ms=0&version=1.9.4&world%5B0%5D%5Bhardcore%5D=false&jvm_arg%5B1%5D=-Xmx2048M&world%5B0%5D%5Bchunks_loaded%5D=272&players_current=0&world%5B1%5D%5Bhardcore%5D=false&world%5B1%5D%5Bgenerator_version%5D=1&jvm_args=2
  

  HTTP/1.1 200 OK
  Date: Fri, 20 May 2016 11:23:15 GMT
  Content-Length: 0
  Connection: keep-alive
  

• ユーザーがログイン(1名)

  POST /server?version=2 HTTP/1.1
  Content-Type: application/x-www-form-urlencoded
  Content-Language: en-US
  Cache-Control: no-cache
  Pragma: no-cache
  User-Agent: Java/1.8.0_92
  Host: snoop.minecraft.net
  Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
  Connection: keep-alive
  Content-Length: 1122
  
  world%5B2%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bchunks_loaded%5D=0&world%5B0%5D%5Bdifficulty%5D=EASY&players_seen=1&world%5B0%5D%5Bgenerator_version%5D=1&world%5B2%5D%5Bdifficulty%5D=EASY&worlds=3&world%5B1%5D%5Bdifficulty%5D=EASY&world%5B0%5D%5Bmode%5D=SURVIVAL&world%5B1%5D%5Bmode%5D=SURVIVAL&gui_state=disabled&world%5B2%5D%5Bhardcore%5D=false&world%5B1%5D%5Bheight%5D=256&world%5B2%5D%5Bheight%5D=256&whitelist_count=0&world%5B1%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bmode%5D=SURVIVAL&snooper_token=91b338ef-cec9-4dcb-b01e-0034393c449f&whitelist_enabled=false&jvm_arg%5B0%5D=-Xms1024M&snooper_count=3&players_max=20&uses_auth=true&world%5B2%5D%5Bdimension%5D=1&world%5B1%5D%5Bdimension%5D=-1&world%5B1%5D%5Bchunks_loaded%5D=0&world%5B0%5D%5Bdimension%5D=0&world%5B0%5D%5Bgenerator_name%5D=default&world%5B2%5D%5Bgenerator_version%5D=1&world%5B0%5D%5Bheight%5D=256&run_time=45023000&avg_tick_ms=6&version=1.9.4&world%5B0%5D%5Bhardcore%5D=false&jvm_arg%5B1%5D=-Xmx2048M&world%5B0%5D%5Bchunks_loaded%5D=522&players_current=1&world%5B1%5D%5Bhardcore%5D=false&world%5B1%5D%5Bgenerator_version%5D=1&jvm_args=2
  

  HTTP/1.1 200 OK
  Date: Fri, 20 May 2016 11:38:15 GMT
  Content-Length: 0
  Connection: keep-alive
  

• 変化する(主な)値
  • snooper_token: 起動のたびに再生成、動作中は一定
  • run_time: 参考→ ​github:Bukkit/mc-dev/blob/master/net/minecraft/server/MinecraftServer.java#L857
  • snooper_count: 送信回数
  • players_current: 現在ログインしているユーザー数