Apache Pool 2 库 - 连接不会自动关闭

Question

我在使用 Apache pool2 库的 Scala 中有以下代码。要池化的对象是 OlapConnection（olap4j class，类似于 SQL 连接）。

问题是当池中对象的数量超过最大值时，我无法让池自动关闭连接。

如果我 return 一个对象到触发 passivateObject 的池（pool.returnObject）。如果我在 passivateObject 中关闭连接，我会在每次 return 对象时关闭它，这不是我想要的 - 我需要缓存打开的连接。如果我不关闭passivateObject中的连接，那么它将永远不会关闭。

如何进行这项工作？

Scala 代码：

class OlapConnectionUtil (val pool: ObjectPool[OlapConnection]) {
     def connect = {
        pool.borrowObject
     }
     def close(olapConnection: OlapConnection) = {
       pool.returnObject(olapConnection)
     }
}

class OlapConnectionFactory extends BasePooledObjectFactory[OlapConnection] {

  override def create = {           
      val connectionString = "jdbc:mondrian:Jdbc=jdbc:mysql://localhost:3306/foodmart?" + 
            "user=x&password=x;Catalog=FoodMart.xml;JdbcDrivers=com.mysql.jdbc.Driver"           
       val connection = DriverManager.getConnection(connectionString)
       connection.unwrap(classOf[OlapConnection])
    }

    override def wrap(olapConnection: OlapConnection) = 
                                  new DefaultPooledObject(olapConnection)

    override def passivateObject(pooledObject: PooledObject[OlapConnection] ) {
      println("passivateObject WAS CALLED")
      pooledObject.getObject.close
    }    

  }


class Test  {

  val olapConnectionFactory = new OlapConnectionFactory

  def test = { 

     val config = new GenericObjectPoolConfig
     config.setMaxIdle(5)
     config.setMaxTotal(10)

     val util = new OlapConnectionUtil(
                 new GenericObjectPool[OlapConnection](olapConnectionFactory,config))
     val olapConnection = util.connect

     // do stuff with olapConnection

     util.close(olapConnection)

Answer 1

如果您打开 PooledObjectFactory 的 JavaDocs，您可能会看到

passivateObject(org.apache.commons.pool2.PooledObject<T>) is invoked on every instance when it is returned to the pool.

destroyObject(org.apache.commons.pool2.PooledObject<T>) is invoked on every instance when it is being "dropped" from the pool (whether due to the response from validateObject(org.apache.commons.pool2.PooledObject<T>), or for reasons specific to the pool implementation.) There is no guarantee that the instance being destroyed will be considered active, passive or in a generally consistent state.

换句话说，您应该将资源解除分配逻辑放入destroyObject。这是你的一个修改后的测试，带有一个假 OlapConnection 实现

import org.apache.commons.pool2._
import org.apache.commons.pool2.impl._

// fake!
case class OlapConnection(val id: Int) {


  def close(): Unit = {
    println(s"Close was called for $this")
  }
}

class OlapConnectionUtil(val pool: ObjectPool[OlapConnection]) {
  def connect = {
    pool.borrowObject
  }

  def close(olapConnection: OlapConnection) = {
    pool.returnObject(olapConnection)
  }
}

class OlapConnectionFactory extends BasePooledObjectFactory[OlapConnection] {
  var cnt = 0

  override def create = {
    cnt += 1
    new OlapConnection(cnt)
  }

  override def wrap(olapConnection: OlapConnection) =
    new DefaultPooledObject(olapConnection)

  override def passivateObject(pooledObject: PooledObject[OlapConnection]) {
    println("-passivateObject was called")
  }

  override def destroyObject(pooledObject: PooledObject[OlapConnection]): Unit = {
    super.destroyObject(pooledObject)
    println("--destroyObject was called")
    pooledObject.getObject.close
  }
}

object Test {

  val olapConnectionFactory = new OlapConnectionFactory

  def test = {

    val config = new GenericObjectPoolConfig
    config.setMaxIdle(5)
    config.setMaxTotal(10)

    val util = new OlapConnectionUtil(new GenericObjectPool[OlapConnection](olapConnectionFactory, config))
    val initConnections = (1 to 10).map(i => util.connect).toList
    val closeCons = initConnections
    Thread.sleep(100)
    println("Start closing")
    closeCons.zipWithIndex.foreach(ci => {
      Thread.sleep(100)
      println(s"Before close ${ci._2 + 1}")
      util.close(ci._1)
      println(s"After close ${ci._2 + 1}")
    })
  }
}

这段代码产生的输出是：

Before close 1
-passivateObject was called
After close 1
Before close 2
-passivateObject was called
After close 2
Before close 3
-passivateObject was called
After close 3
Before close 4
-passivateObject was called
After close 4
Before close 5
-passivateObject was called
After close 5
Before close 6
-passivateObject was called
--destroyObject was called
Close was called for OlapConnection(6)
After close 6
Before close 7
-passivateObject was called
--destroyObject was called
Close was called for OlapConnection(7)
After close 7
Before close 8
-passivateObject was called
--destroyObject was called
Close was called for OlapConnection(8)
After close 8
Before close 9
-passivateObject was called
--destroyObject was called
Close was called for OlapConnection(9)
After close 9
Before close 10
-passivateObject was called
--destroyObject was called
Close was called for OlapConnection(10)
After close 10

如您在此输出中所见，close 自 OlapConnection(6) 以来被调用，正如人们所期望的给定池配置。

Apache Pool 2 库 - 连接不会自动关闭

Apache Pool 2 library - connections not closed automatically

scala

olap4j

apache-commons-pool