DBCP 1.4 BUG 导致连接池爆满解决方案
dubbo 项目用的 commons-dbcp-1.4 和 commons-pool-1.5.4 实现连接池，导致数据库经常爆满，经过调试，发现了个 dbcp的bug：
dbcp 源码：
BasicDataSource.java
创建datasource的方法：
protected synchronized DataSource createDataSource()
throws SQLException {
if (closed) {
throw new SQLException("Data source is closed");
}
// Return the pool if we have already created it
if (dataSource != null) {
return (dataSource);
}
// create factory which returns raw physical connections
ConnectionFactory driverConnectionFactory = createConnectionFactory();
// create a pool for our connections
createConnectionPool();
// Set up statement pool, if desired
GenericKeyedObjectPoolFactory statementPoolFactory = null;
if (isPoolPreparedStatements()) {
statementPoolFactory = new GenericKeyedObjectPoolFactory(null,
-1, // unlimited maxActive (per key)
GenericKeyedObjectPool.WHEN_EXHAUSTED_FAIL,
0, // maxWait
1, // maxIdle (per key)
maxOpenPreparedStatements);
}
// Set up the poolable connection factory
createPoolableConnectionFactory(driverConnectionFactory, statementPoolFactory, abandonedConfig);
// Create and return the pooling data source to manage the connections
createDataSourceInstance();
try {
for (int i = 0 ; i < initialSize ; i++) {
connectionPool.addObject();
}
} catch (Exception e) {
throw new SQLNestedException("Error preloading the connection pool", e);
}
return dataSource;
}
该方法先 调用 createConnectionPool() 方法 创建 connectionPool，
接着 调用 createPoolableConnectionFactory() 方法创建 connectionFactory,
最后 再调用 createDataSourceInstance() 方法创建 datasource
看看 createConnectionPool() 方法实现：
protected void createConnectionPool() {
// Create an object pool to contain our active connections
GenericObjectPool gop;
if ((abandonedConfig != null) && (abandonedConfig.getRemoveAbandoned())) {
gop = new AbandonedObjectPool(null,abandonedConfig);
}
else {
gop = new GenericObjectPool();
}
gop.setMaxActive(maxActive);
gop.setMaxIdle(maxIdle);
gop.setMinIdle(minIdle);
gop.setMaxWait(maxWait);
gop.setTestOnBorrow(testOnBorrow);
gop.setTestOnReturn(testOnReturn);
gop.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
gop.setNumTestsPerEvictionRun(numTestsPerEvictionRun);
gop.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
gop.setTestWhileIdle(testWhileIdle);
connectionPool = gop;
}
这个方法是：每次调用都会创建一个connectionPool，并且都是直接new 的，
问题：
当创建 connectionPool成功，但是创建connectionFactory失败，也就是说createConnectionPool()成功了，但是createPoolableConnectionFactory()出现异常了，则dataSource也创建失败，系统会再次执行 createDataSource() 方法，会再次创建一个新的 coonnectionPool , 我的系统里，一共尝试创建了 15次都失败，最后16次才成功，所以也就创建了16个connectionPool,每一个pool的连接数会至少等于 minIdel 的数量，结果导致数据库连接爆满。。。
解决:
修改 createConnectionPool() 方法实现,添加非空判断：
protected void createConnectionPool() {
//添加非空判断
if(gop != null){
return ;
}
// Create an object pool to contain our active connections
GenericObjectPool gop;
if ((abandonedConfig != null) && (abandonedConfig.getRemoveAbandoned())) {
gop = new AbandonedObjectPool(null,abandonedConfig);
}
else {
gop = new GenericObjectPool();
}
gop.setMaxActive(maxActive);
gop.setMaxIdle(maxIdle);
gop.setMinIdle(minIdle);
gop.setMaxWait(maxWait);
gop.setTestOnBorrow(testOnBorrow);
gop.setTestOnReturn(testOnReturn);
gop.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
gop.setNumTestsPerEvictionRun(numTestsPerEvictionRun);
gop.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
gop.setTestWhileIdle(testWhileIdle);
connectionPool = gop;
}
至此：问题解决。
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