https://issues.apache.org/bugzilla/show_bug.cgi?id=50805
Summary: Leak & Performance issue of getConnectionAsync()
Product: Tomcat Modules
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: jdbc-pool
AssignedTo: dev@tomcat.apache.org
ReportedBy: mashm...@gmail.com
Created an attachment (id=26677)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=26677)
patch for ConnectionPool
Leak and performance issue occurs when using getConnectionAsync().
getConnectionAsync() calls borrowConnection(int, String, String), and add
PooledConnection to the busy queue.
future.get() also calls borrowConnection(long, PooledConnection, String,
String), and same PooledConnection is added to the busy queue again.
The first connection is removed from the busy queue when returnConnection() is
called, but the second one remains as garbage.
The busy queue overflows at once because of these garbage connection.
Int this time, ConnectionPool.size is smaller than busy queue size. And new
real connection is created when getConnectionAsync() is called.
And, when the busy queue overflows, the connection is released in
ConnectionPool.returnConnection(). This causes the problem of the performance.
---
Furthermore, in most case the following codes are not executed, because
borrowConnection(int, String, String) is not returned null except as validation
failed.
149 if (idle instanceof FairBlockingQueue<?>) {
150 Future<PooledConnection> pcf =
((FairBlockingQueue<PooledConnection>)idle).pollAsync();
151 return new ConnectionFuture(pcf);
152 } else if (idle instanceof MultiLockFairBlockingQueue<?>) {
153 Future<PooledConnection> pcf =
((MultiLockFairBlockingQueue<PooledConnection>)idle).pollAsync();
154 return new ConnectionFuture(pcf);
155 } else {
156 throw new SQLException("Connection pool is misconfigured,
doesn't support async retrieval. Set the 'fair' property to 'true'");
157 }
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Based on above, I improved the getConnectionAsync().
Best regards.
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