MySQL INSERT on SELECT Deadlock 多人游戏答案

【问题标题】：MySQL INSERT on SELECT Deadlock multiplayer gameMySQL INSERT on SELECT Deadlock 多人游戏
【发布时间】：2017-12-10 18:19:27
【问题描述】：

MySQL 版本：5.7
存储引擎：InnoDB
为了让您了解这是一个纸牌游戏（在 nodejs 中）。在这种情况下，一个 9 人桌面游戏。每个玩家可以同时玩 4 个桌面游戏。

最近我面临着反复出现的死锁，例如 1K 并发用户每分钟 1 到 5 次。下面的查询被称为平均每分钟和每个用户 2 次。

用户想玩。
服务器总是在第一个可用的桌面游戏中找到第一个空位（座位）。

我不知道如何解决这个问题，因为此查询旨在处理 2 个以上不同玩家（或同一玩家 2 次以上）执行插入查询时可能出现的竞争条件。

当然，我可以通过唯一键处理竞争条件，但在 100 多个用户搜索空闲位置的高峰时，我无法管理。可证明它会通过重复键导致 91+ 拒绝。

LATEST DETECTED DEADLOCK
------------------------

*** (1) TRANSACTION:
TRANSACTION 100539324, ACTIVE 0 sec inserting
mysql tables in use 5, locked 5
LOCK WAIT 23 lock struct(s), heap size 3520, 111 row lock(s), undo log entries 1
MySQL thread id 6782, OS thread handle 2460, query id 138188765 localhost 127.0.0.1 root Creating sort index
INSERT INTO app_tables_players (user_id, game_id, seat_number, username, state, folded) SELECT 597, a.id, b.id AS seat_number, 'some_username', 'temp', false FROM (SELECT id FROM app_tables_games WHERE table_id = 6 AND seats_total > seats_taken AND id NOT IN (SELECT game_id FROM app_users_state WHERE user_id = 597)) AS a, `app_temp_players_9` AS b WHERE b.id NOT IN (SELECT seat_number FROM app_tables_players WHERE game_id = a.id) ORDER BY a.id ASC LIMIT 1

*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 75 page no 51 n bits 1120 index seat_number_game_id of table `nodejs`.`app_tables_players` trx id 100539324 lock_mode X locks gap before rec insert intention waiting
Record lock, heap no 964 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d8f6; asc     ;;
 2: len 4; hex 006b437b; asc  kC{;;

*** (2) TRANSACTION:
TRANSACTION 100539325, ACTIVE 0 sec setting auto-inc lock, thread declared inside InnoDB 4743
mysql tables in use 5, locked 5
22 lock struct(s), heap size 3520, 151 row lock(s)
MySQL thread id 6702, OS thread handle 11428, query id 138188764 localhost 127.0.0.1 root Creating sort index
INSERT INTO app_tables_players (user_id, game_id, seat_number, username, state, folded) SELECT 613, a.id, b.id AS seat_number, 'some_username2', 'tmp', false FROM (SELECT id FROM app_tables_games WHERE table_id = 14 AND seats_total > seats_taken AND id NOT IN (SELECT game_id FROM app_users_state WHERE user_id = 613)) AS a, `app_temp_players_9` AS b WHERE b.id NOT IN (SELECT seat_number FROM app_tables_players WHERE game_id = a.id) ORDER BY a.id ASC LIMIT 1

*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 75 page no 51 n bits 1120 index seat_number_game_id of table `nodejs`.`app_tables_players` trx id 100539325 lock mode S locks gap before rec
Record lock, heap no 18 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 06; asc  ;;
 1: len 4; hex 0008d6e4; asc     ;;
 2: len 4; hex 006b5a47; asc  kZG;;

Record lock, heap no 97 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d97e; asc    ~;;
 2: len 4; hex 006b5d1e; asc  k] ;;

Record lock, heap no 160 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 05; asc  ;;
 1: len 4; hex 0008d93e; asc    >;;
 2: len 4; hex 006b4cb3; asc  kL ;;

Record lock, heap no 181 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d92f; asc    /;;
 2: len 4; hex 006b5c0b; asc  k\ ;;

Record lock, heap no 267 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d9b2; asc     ;;
 2: len 4; hex 006b5b9a; asc  k[ ;;

Record lock, heap no 272 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 05; asc  ;;
 1: len 4; hex 0008d999; asc     ;;
 2: len 4; hex 006b5d43; asc  k]C;;

Record lock, heap no 307 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008da33; asc    3;;
 2: len 4; hex 006b6182; asc  ka ;;

Record lock, heap no 346 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008da38; asc    8;;
 2: len 4; hex 006b5fbd; asc  k_ ;;

Record lock, heap no 530 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 05; asc  ;;
 1: len 4; hex 0008d9b2; asc     ;;
 2: len 4; hex 006b544e; asc  kTN;;

Record lock, heap no 556 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 05; asc  ;;
 1: len 4; hex 0008d97e; asc    ~;;
 2: len 4; hex 006b62f3; asc  kb ;;

Record lock, heap no 629 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d999; asc     ;;
 2: len 4; hex 006b5f41; asc  k_A;;

Record lock, heap no 804 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 05; asc  ;;
 1: len 4; hex 0008da33; asc    3;;
 2: len 4; hex 006b60bc; asc  k` ;;

Record lock, heap no 906 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d93e; asc    >;;
 2: len 4; hex 006b4988; asc  kI ;;

Record lock, heap no 962 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d928; asc    (;;
 2: len 4; hex 006b5b03; asc  k[ ;;

Record lock, heap no 964 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
 0: len 1; hex 04; asc  ;;
 1: len 4; hex 0008d8f6; asc     ;;
 2: len 4; hex 006b437b; asc  kC{;;

*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
TABLE LOCK table `nodejs`.`app_tables_players` trx id 100539325 lock mode AUTO-INC waiting
*** WE ROLL BACK TRANSACTION (2)

导致问题的查询：

INSERT INTO app_tables_players
    (user_id, 
    game_id, 
    seat_number) 
SELECT
    597, 
    a.id, 
    b.id AS seat_number
FROM 
    (SELECT id 
    FROM
        app_tables_games 
    WHERE
        table_id = 14
        AND seats_total > seats_taken 
        AND id NOT IN (
            SELECT game_id 
            FROM   app_users_state 
            WHERE  user_id = 597
        )
    ) AS a, 
    app_temp_players_9 AS b 
WHERE
    b.id NOT IN (
        SELECT seat_number 
        FROM   app_tables_players 
        WHERE  game_id = a.id
    ) 
ORDER BY a.id ASC 
LIMIT 1;

解释查询：

id, select_type, table, partitions, type, possible_keys, key, key_len, ref, rows, filtered, Extra

1, INSERT, app_tables_players, , ALL, , , , , , ,

1, PRIMARY, app_tables_games, , ref, table_id,table_id_seats_taken_seats_total, table_id_seats_taken_seats_total, 4, const, 24, 33.33, Using where; Using index; Using temporary; Using filesort

1, PRIMARY, b, , index, , id, 1, , 9, 100.00, Using where; Using index; Using join buffer (Block Nested Loop)

4, DEPENDENT SUBQUERY, app_tables_players, , index_subquery, seat_number_game_id,game_id_user_id,game_id,seat_number,game_id_state, seat_number_game_id, 6, func,func, 2, 100.00, Using where; Using index

3, SUBQUERY, app_users_state, , ref, game_id_user_id,user_id,game_id, user_id, 4, const, 4, 100.00,

小提琴： http://sqlfiddle.com/#!9/fe63f7

注意：有时上面的查询会发生死锁，并且：

DELETE FROM app_users_states WHERE game_id = some_id AND user_id = some_id

【问题讨论】：

标签： mysql database deadlock database-deadlocks

【解决方案1】：

在对该应用程序中面临的所有死锁进行更多研究后，我发现有 2-3 种不同的类型或情况。

其中一个是lock mode AUTO-INC waiting

因此，第一个事务锁定了自动增量 id 列并等待索引“X”，第二个事务锁定索引“X”并等待 AUTO-INC 锁定。

因为我需要id 列来获取lastInsertId 并稍后在SELECT 中使用它，所以必须有这个自动增量列。为了解决这个问题，我在我的应用程序中创建了一个已知的UUID 值并存储为二进制（16）而不是自动增量 intid。

第二个和第三个问题与同一查询中不同或同一表中的SELECT 上的INSERT 有关。喜欢（简单的例子）；

INSERT INTO tableA some_colX (SELECT some_colY FROM tableA WHERE some_colZ = 1 LIMIT 1)

这个SELECTs 使用了lock mode S locks gap before rec，但INSERT 需要lock_mode X locks gap before rec insert intention waiting。在我的 INSERT 中，我在 3 个不同的表中执行 SELECTs，而在应用程序的其他部分，还有一些其他的 UPDATEs 或其他的 INSERTs，所以到处都有很多死锁。

为了解决部分问题，我更改了（部分）SELECTs 在 de INSERT 语句中添加了 FOR UPDATE，因此设置了 IX lock 而不是 S lock，防止其他查询首先获得X lock in this record/gap

我后来意识到，我的应用程序中出现了另一个死锁。你认为呢？在其他完全不同的表中查询SELECT 上的另一个不同（也是最新的）INSERT。

从每分钟 1 到 5 个死锁到每 10 分钟或更长时间 1 个死锁。

所以，作为我个人的意见（用例），不要在同一个查询中使用INSERT 和SELECT。使用过程、事务...并检查SELECTs 是否使用了正确的索引。

对不起我的英语:)

祝你好运。

更新：

将主表中的 1 个索引更改为 de INSERT 和 SELECT 表之一上的 1 个索引。结果：到目前为止，2 小时内 0 个死锁

【讨论】：