174 lines
6.5 KiB
Markdown
174 lines
6.5 KiB
Markdown
关于事务超时
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===========================
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OceanBase 为了避免事务长时间不提交持有锁影响其他会话，设计了两个超时逻辑。一个是事务空闲超时，一个是事务未提交超时。分别由租户变量 ob_trx_idle_timeout 和 ob_trx_timeout 控制，默认值分别是 120 秒和 100 秒。通常只会有一个超时机制被触发。
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**说明**
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建议变量 ob_trx_idle_timeout 使用默认值。
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```javascript
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obclient> show variables where variable_name in ('ob_trx_idle_timeout','ob_trx_timeout');
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+---------------------+-----------+
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| VARIABLE_NAME | VALUE |
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+---------------------+-----------+
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| ob_trx_idle_timeout | 120000000 |
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| ob_trx_timeout | 100000000 |
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+---------------------+-----------+
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2 rows in set (0.00 sec)
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```
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关于事务空闲超时
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-----------------
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OceanBase 的事务空闲时间超过一段时间还没有提交时，会自动断开连接并回滚事务，此时会话需要重新连接。
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会话事务空闲超时时间阈值由租户变量 ob_trx_idle_timeout 控制，这个参数值建议使用默认值 120 秒，实际空闲会话断开的时间会是在 \[100s, 100s + ob_trx_idle_timeout \] 之间。
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#### 示例：事务空闲超时报错
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下面示例先设置事务空闲超时时间为 120 秒，事务未提交超时时间为 1000 秒。当事务空闲时间超过 120 秒后，连接会被自动断开，事务也自动被 ROLLBACK 了。
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```javascript
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obclient> DROP TABLE IF EXISTS t_insert;
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Query OK, 0 rows affected (0.01 sec)
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obclient> CREATE TABLE t_insert(
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id bigint NOT NULL PRIMARY KEY auto_increment
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, name varchar(10) NOT NULL
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, value bigint
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,gmt_create timestamp NOT NULL DEFAULT current_timestamp
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);
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Query OK, 0 rows affected (0.05 sec)
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obclient> INSERT INTO t_insert(name, value) values('CN',NULL),('UK',NULL),('US',NULL);
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Query OK, 3 rows affected (0.00 sec)
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Records: 3 Duplicates: 0 Warnings: 0
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obclient> select now(), * from t_insert t;
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+---------------------+----+------+-------+---------------------+
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| now() | id | name | value | gmt_create |
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+---------------------+----+------+-------+---------------------+
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| 2020-04-03 16:54:51 | 1 | CN | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:54:51 | 2 | UK | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:54:51 | 3 | US | NULL | 2020-04-03 16:54:49 |
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+---------------------+----+------+-------+---------------------+
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3 rows in set (0.00 sec)
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obclient> set session ob_trx_timeout=1000000000;
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Query OK, 0 rows affected (0.00 sec)
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obclient> set session ob_trx_idle_timeout=120000000;
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Query OK, 0 rows affected (0.00 sec)
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obclient> begin;
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Query OK, 0 rows affected (0.00 sec)
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obclient> update t_insert set gmt_create=now() where id=3;
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Query OK, 1 row affected (0.00 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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obclient> select now(), t.* from t_insert t;
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+---------------------+----+------+-------+---------------------+
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| now() | id | name | value | gmt_create |
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+---------------------+----+------+-------+---------------------+
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| 2020-04-03 16:55:30 | 1 | CN | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:55:30 | 2 | UK | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:55:30 | 3 | US | NULL | 2020-04-03 16:55:25 |
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+---------------------+----+------+-------+---------------------+
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3 rows in set (0.00 sec)
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<<等 100 秒不操作>>
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obclient> select now(), t.* from t_insert t;
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ERROR-02013: Lost connection to MySQL server during query
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obclient> select now(), * from t_insert t;
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ERROR-02006: MySQL server has gone away
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No connection. Trying to reconnect...
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Connection id: 53246
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Current database: TPCC
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+---------------------+----+------+-------+---------------------+
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| now() | id | name | value | gmt_create |
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+---------------------+----+------+-------+---------------------+
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| 2020-04-03 16:57:41 | 1 | CN | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:57:41 | 2 | UK | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:57:41 | 3 | US | NULL | 2020-04-03 16:54:49 |
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+---------------------+----+------+-------+---------------------+
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3 rows in set (0.00 sec)
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```
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关于事务未提交超时
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------------------
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OceanBase 的事务持续时间超过一段时间还没有提交，会报超时错误。此时会话需要明确发出 ROLLBACK 命令才可以继续在会话里执行 SQL。
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会话事务的未提交超时时间阈值是由租户变量 ob_trx_timeout 控制。
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#### 示例：事务未提交超时报错
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下面示例先设置事务空闲超时时间为 120 秒，事务超时时间为 100 秒。当一个事务未提交时间持续到 100 秒时，事务内部状态就变为超时状态，同时锁会释放。此后会话需要显式发出 ROLLBACK 语句。
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```javascript
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obclient> set session ob_trx_timeout=100000000;
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Query OK, 0 rows affected (0.00 sec)
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obclient> set session ob_trx_idle_timeout=120000000;
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Query OK, 0 rows affected (0.00 sec)
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obclient> begin;
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Query OK, 0 rows affected (0.00 sec)
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obclient> update t_insert set gmt_create=sysdate() where id=3;
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Query OK, 1 row affected (0.00 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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obclient> select now(), t.* from t_insert t ;
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+---------------------+----+------+-------+---------------------+
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| now() | id | name | value | gmt_create |
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+---------------------+----+------+-------+---------------------+
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| 2020-04-03 16:59:56 | 1 | CN | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:59:56 | 2 | UK | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 16:59:56 | 3 | US | NULL | 2020-04-03 16:59:51 |
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+---------------------+----+------+-------+---------------------+
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3 rows in set (0.00 sec)
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<<等 120 秒不操作>>
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obclient> select now(), t.* from t_insert t ;
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ERROR-00600: internal error code, arguments: -6210, Transaction is timeout
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obclient> commit;
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ERROR-00600: internal error code, arguments: -6210, Transaction is timeout
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obclient> rollback;
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Query OK, 0 rows affected (0.00 sec)
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obclient> select now(), t.* from t_insert t ;
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+---------------------+----+------+-------+---------------------+
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| now() | id | name | value | gmt_create |
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+---------------------+----+------+-------+---------------------+
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| 2020-04-03 17:04:13 | 1 | CN | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 17:04:13 | 2 | UK | NULL | 2020-04-03 16:54:49 |
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| 2020-04-03 17:04:13 | 3 | US | NULL | 2020-04-03 16:54:49 |
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+---------------------+----+------+-------+---------------------+
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3 rows in set (0.00 sec)
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```
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**说明**
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建议不要将事务未提交超时参数设置小于 1 秒。
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