java - 为什么我的Tomcat只打开8个JDBC连接

Question

在 Tomcat 8 中设置数据库连接时，由于某种原因，Tomcat 没有遵循我在 context.xml 中配置的内容，结果我用完了连接，导致应用程序服务器端发生资源争用(阻塞/等待线程)。池初始化后，我总是有 8 个连接(在 mariadb/mysql 中显示进程列表)。我的配置规定最少 10 个连接，最多 100 个连接。

我测试了不同的配置，但这根本没有任何区别，至少这很奇怪。使用 context.xml 否则它根本无法连接到数据库。

这里发生了什么？为什么只有 8 个连接？

软件版本:- MySQL JDBC 驱动程序:最新 (5.1.35)- Java 1.8.0_05

我还观察到我以前的设置:Tomcat 7、Java 1.7、较旧的 MySQL JDBC 驱动程序、MySQL 而不是 MariaDB。所以问题似乎与版本没有直接关系。

显示进程列表输出(显示 8 个进程):

| Id    | User          | Host          | db                | Command | Time | State     | Info            | Progress |                                                                     
+-------+---------------+---------------+-------------------+---------+------+-----------+-----------------+----------+
| 71153 | root          | localhost     | vnitdatacollector | Query   |    0 | init      | show processlist|    0.000 |                                                                     
| 73473 | vnit_datacoll | virt005:58585 | vnitdatacollector | Sleep   |    0 |           | NULL            |    0.000 |                                                                     
| 73474 | vnit_datacoll | virt005:58586 | vnitdatacollector | Sleep   |    0 |           | NULL            |    0.000 |                                                                     
| 73482 | vnit_datacoll | virt005:58606 | vnitdatacollector | Query   |    0 | update    | INSERT INTO ... |    0.000 |
| 73483 | vnit_datacoll | virt005:58607 | vnitdatacollector | Sleep   |    0 |           | NULL            |    0.000 |                                                                     
| 73485 | vnit_datacoll | virt005:58618 | vnitdatacollector | Query   |    0 | query end | INSERT INTO ... |    0.000 |
| 73487 | vnit_datacoll | virt005:58624 | vnitdatacollector | Sleep   |    0 |           | NULL            |    0.000 |                                                                     
| 73488 | vnit_datacoll | virt005:58634 | vnitdatacollector | Sleep   |    0 |           | NULL            |    0.000 |                                                                     
| 73489 | vnit_datacoll | virt005:58637 | vnitdatacollector | Query   |    7 | update    | INSERT INTO ... |    0.000 |
+-------+---------------+---------------+-------------------+---------+------+-----------+-----------------+----------+

我有以下 context.xml 配置:

<?xml version="1.0" encoding="UTF-8"?>
<Context>
  <Resource 
    name="jdbc/dbaccess" 
    auth="Container" 
    type="javax.sql.DataSource"
    maxActive="100" 
    maxIdle="100"
    minIdle="10"
    maxWait="1000"
    initialSize="10"
    minEvictableIdleTimeMillis="5000"
    testOnBorrow="true"
    validationQuery="SELECT 1" 
    timeBetweenEvictionRunsMillis="5000" 
    testWhileIdle="true"
    removeAbandoned="true" 
    removeAbandonedTimeout="60" 
    logAbandoned="true"
    username="some_user" 
    password="{the password}" 
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://dbserver:3306/dbaccess?useFastDateParsing=false&amp;jdbcCompliantTruncation=false"
  />
  <Resource
    name="mail/emailconnection"
    auth="Container"
    type="javax.mail.Session"
    mail.smtp.host="some.stmp.server"
  />             
</Context>

在(短)时间后出现以下线程问题:

"Thread-495" #517 daemon prio=5 os_prio=0 tid=0x00007f678c040800 nid=0x1642 waiting on condition [0x00007f67848f4000]
java.lang.Thread.State: WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x00000000f21933f0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
    at org.apache.tomcat.dbcp.pool2.impl.LinkedBlockingDeque.takeFirst(LinkedBlockingDeque.java:582)
    at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:439)
    at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:360)
    at org.apache.tomcat.dbcp.dbcp2.PoolingDataSource.getConnection(PoolingDataSource.java:118)
    at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:1412)
    at com.hipersonik.util.ServiceLocator.getConnection(ServiceLocator.java:32)

Answer 1

引自“Tomcat Expert: Configuring jdbc-pool for high-concurrency”:

When Tomcat reads the type="javax.sql.DataSource" it will automatically configure its repackaged DBCP, unless you specify a different factory. The factory object is what creates and configures the connection pool itself.

原来DBCP包只是忽略了一系列的设置。在context.xml 资源配置中添加以下行，在数据库中得到更好的响应:

<Resource 
 ....
factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
 ....
/>

在 mysql 中显示进程列表，然后立即显示所需的行为。