querylist 多线程是什么意思
发布网友
发布时间：2022-04-23 02:15
共2个回答
懂视网
时间：2022-05-01 22:56
二、dbcp2
public class DataBaseHelper {
// 保证一个线程一个Connection，线程安全
private static final ThreadLocal<Connection> connHolder;
// 线程池
private static final BasicDataSource dataSource;
static {
connHolder = new ThreadLocal<Connection>();
dataSource = new BasicDataSource();
dataSource.setDriverClassName("org.postgresql.Driver");
dataSource.setUrl("jdbc:postgresql://数据库地址:数据库端口/freeswitch");
dataSource.setUsername("freeswitch");
dataSource.setPassword("freeswitch");
/// 设置空闲和借用的连接的最大总数量，同时可以激活。
dataSource.setMaxTotal(60);
// 设置初始大小
dataSource.setInitialSize(5);
// 最小空闲连接
dataSource.setMinIdle(8);
// 最大空闲连接
dataSource.setMaxIdle(16);
// 超时等待时间毫秒
dataSource.setMaxWaitMillis(2 * 10000);
// 只会发现当前连接失效，再创建一个连接供当前查询使用
dataSource.setTestOnBorrow(true);
// removeAbandonedTimeout ：超过时间限制，回收没有用(废弃)的连接（默认为 300秒，调整为180）
dataSource.setRemoveAbandonedTimeout(180);
// removeAbandoned ：超过removeAbandonedTimeout时间后，是否进
// 行没用连接（废弃）的回收（默认为false，调整为true)
// DATA_SOURCE.setRemoveAbandonedOnMaintenance(removeAbandonedOnMaintenance);
dataSource.setRemoveAbandonedOnBorrow(true);
// testWhileIdle
dataSource.setTestOnReturn(true);
// testOnReturn
dataSource.setTestOnReturn(true);
// setRemoveAbandonedOnMaintenance
dataSource.setRemoveAbandonedOnMaintenance(true);
// 记录日志
dataSource.setLogAbandoned(true);
// 设置自动提交
dataSource.setDefaultAutoCommit(true);
}
/**
* 获取数据库连接
*/
public static Connection getConnection() {
Connection conn = connHolder.get();
if (conn == null) {
try {
conn = dataSource.getConnection();
System.out.println("get connection success");
} catch (SQLException e) {
System.out.println("get connection failure:" + e);
} finally {
connHolder.set(conn);
}
}
return conn;
}
/**
* 关闭数据库连接
*/
public static void closeConnection() {
Connection conn = connHolder.get();
if (conn != null) {
try {
conn.close();
System.out.println("close connection success");
} catch (SQLException e) {
System.out.println("close connection failure:" + e);
throw new RuntimeException(e);
} finally {
connHolder.remove();
}
}
}
}
线程池c3p0和dbcp2的配置初始化实例
标签：span commit sys ota 限制 mini cdata 取数 auto
热心网友
时间：2022-05-01 20:04
我们来演示下。
线程A，我们用来锁定某些记录，假设这个线程一直没提交，或者忘掉提交了。 那么就一直存在，但是数据里面显示的只是SLEEP状态。
mysql> set @@autocommit=0;
Query OK, 0 rows affected (0.00 sec)
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| demo_test |
| t3 |
+----------------+
2 rows in set (0.00 sec)
mysql> select * from t3;
+----+--------+--------+------------+----+----+----+
| id | fname | lname | birthday | c1 | c2 | c3 |
+----+--------+--------+------------+----+----+----+
| 19 | lily19 | lucy19 | 2013-04-18 | 19 | 0 | 0 |
| 20 | lily20 | lucy20 | 2013-03-13 | 20 | 0 | 0 |
+----+--------+--------+------------+----+----+----+
2 rows in set (0.00 sec)
mysql> update t3 set birthday = '2022-02-23' where id = 19;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select connection_id();
+-----------------+
| connection_id() |
+-----------------+
| 16 |
+-----------------+
1 row in set (0.00 sec)
mysql>
线程B， 我们用来进行普通的更新，但是遇到问题了，此时不知道是哪个线程把这行记录给锁定了?
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)
mysql> update t3 set birthday='2018-01-03' where id = 19;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
mysql> select connection_id();
+-----------------+
| connection_id() |
+-----------------+
| 17 |
+-----------------+
1 row in set (0.00 sec)
mysql> show processlist;
+----+------+-----------+------+---------+------+-------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------+-----------+------+---------+------+-------+------------------+
| 10 | root | localhost | NULL | Sleep | 1540 | | NULL |
| 11 | root | localhost | NULL | Sleep | 722 | | NULL |
| 16 | root | localhost | test | Sleep | 424 | | NULL |
| 17 | root | localhost | test | Query | 0 | init | show processlist |
| 18 | root | localhost | NULL | Sleep | 5 | | NULL |
+----+------+-----------+------+---------+------+-------+------------------+
5 rows in set (0.00 sec)
mysql> show engine innodb status\G
------------
TRANSACTIONS
------------
Trx id counter 189327
Purge done for trx's n:o < 189323 undo n:o < 0 state: running but idle
History list length 343
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 11, OS thread handle 0x7f70a0c98700, query id 994 localhost root init
show engine innodb status
---TRANSACTION 189326, ACTIVE 2 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 376, 1 row lock(s)
MySQL thread id 17, OS thread handle 0x7f70a0bd5700, query id 993 localhost root updating
update t3 set birthday='2018-01-03' where id = 19
------- TRX HAS BEEN WAITING 2 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 529 page no 3 n bits 72 index `PRIMARY` of table `test`.`t3` trx id 189326 lock_mode X waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 9; compact format; info bits 0
0: len 2; hex 3139; asc 19;;
1: len 6; hex 00000002e38c; asc ;;
2: len 7; hex 7e00000d2827c9; asc ~ (' ;;
3: len 6; hex 6c696c793139; asc lily19;;
4: len 6; hex 6c7563793139; asc lucy19;;
5: len 3; hex 8fcc57; asc W;;
6: len 4; hex 80000013; asc ;;
7: len 4; hex 80000000; asc ;;
8: len 4; hex 80000000; asc ;;
------------------
---TRANSACTION 189324, ACTIVE 641 sec
2 lock struct(s), heap size 376, 3 row lock(s), undo log entries 1
MySQL thread id 16, OS thread handle 0x7f70a0b94700, query id 985 localhost root cleaning up
Trx read view will not see trx with id >= 189325, sees < 189325
上面的信息很繁多，也看不清楚到底哪里是哪里。
不过现在，我们只要从数据字典里面拿出来这部分信息就OK了。
mysql> SELECT * FROM information_schema.INNODB_TRX\G
*************************** 1. row ***************************
trx_id: 189324
trx_state: RUNNING
trx_started: 2013-04-18 17:48:14
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 3
trx_mysql_thread_id: 16
trx_query: NULL
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 0
trx_lock_structs: 2
trx_lock_memory_bytes: 376
trx_rows_locked: 3
trx_rows_modified: 1
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_adaptive_hash_latched: 0
trx_adaptive_hash_timeout: 10000
trx_is_read_only: 0
trx_autocommit_non_locking: 0
1 row in set (0.01 sec)
mysql>
原来是线程16忘掉COMMIT了。
