com.mysql.cj.jdbc

Class AbandonedConnectionCleanupThread

java.lang.Object

com.mysql.cj.jdbc.AbandonedConnectionCleanupThread

All Implemented Interfaces:

java.lang.Runnable

public class AbandonedConnectionCleanupThread
extends java.lang.Object
implements java.lang.Runnable

This class implements a thread that is responsible for closing abandoned MySQL connections, i.e., connections that are not explicitly closed. There is only one instance of this class and there is a single thread to do this task. This thread's executor is statically referenced in this same class.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference PhantomReference subclass to track MysqlConnection objects finalization.

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	abandonedConnectionCleanupDisabled
private static java.util.concurrent.ExecutorService	cleanupThreadExecutorService
private static java.util.Set<AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference>	connectionFinalizerPhantomRefs
private static java.lang.ref.ReferenceQueue<MysqlConnection>	referenceQueue
private static java.lang.Thread	threadRef
private static java.util.concurrent.locks.Lock	threadRefLock

Constructor Summary

Constructors

Modifier	Constructor and Description
private	AbandonedConnectionCleanupThread()

Method Summary

Modifier and Type	Method and Description
static void	checkedShutdown() Performs a checked shutdown, i.e., the context ClassLoaders from this and the caller thread are checked for consistency prior to performing the shutdown operation.
private void	checkThreadContextClassLoader() Checks if the thread's context ClassLoader is active.
private static boolean	consistentClassLoaders() Checks if the context ClassLoaders from this and the caller thread are the same.
private static void	finalizeResource(AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference reference) Release resources from the given AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference and remove it from the references set.
static boolean	isAlive() Returns true if the working thread is alive.
void	run()
private static void	shutdown(boolean checked) Shuts down this thread either checking or not the context ClassLoaders from the involved threads.
protected static void	trackConnection(MysqlConnection conn, NetworkResources io) Tracks the finalization of a MysqlConnection object and keeps a reference to its NetworkResources so that they can be later released.
static void	uncheckedShutdown() Performs an unchecked shutdown, i.e., the shutdown is performed independently of the context ClassLoaders from the involved threads.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

connectionFinalizerPhantomRefs

private static final java.util.Set<AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference> connectionFinalizerPhantomRefs

referenceQueue

private static final java.lang.ref.ReferenceQueue<MysqlConnection> referenceQueue

cleanupThreadExecutorService

private static final java.util.concurrent.ExecutorService cleanupThreadExecutorService

threadRef

private static java.lang.Thread threadRef

threadRefLock

private static java.util.concurrent.locks.Lock threadRefLock

abandonedConnectionCleanupDisabled

private static boolean abandonedConnectionCleanupDisabled

Constructor Detail

AbandonedConnectionCleanupThread

private AbandonedConnectionCleanupThread()

Method Detail

run

public void run()

Specified by:

run in interface java.lang.Runnable

checkThreadContextClassLoader

private void checkThreadContextClassLoader()

Checks if the thread's context ClassLoader is active. This is usually true but some application managers implement a life-cycle mechanism in their ClassLoaders that is linked to the corresponding application's life-cycle. As such, a stopped/ended application will have a ClassLoader unable to load anything and, eventually, they throw an exception when trying to do so. When this happens, this thread has no point in being alive anymore.

consistentClassLoaders

private static boolean consistentClassLoaders()

Checks if the context ClassLoaders from this and the caller thread are the same.

Returns:

true if both threads share the same context ClassLoader, false otherwise

shutdown

private static void shutdown(boolean checked)

Shuts down this thread either checking or not the context ClassLoaders from the involved threads.

Parameters:

checked - does a checked shutdown if true, unchecked otherwise

checkedShutdown

public static void checkedShutdown()

Performs a checked shutdown, i.e., the context ClassLoaders from this and the caller thread are checked for consistency prior to performing the shutdown operation.

uncheckedShutdown

public static void uncheckedShutdown()

Performs an unchecked shutdown, i.e., the shutdown is performed independently of the context ClassLoaders from the involved threads.

isAlive

public static boolean isAlive()

Returns true if the working thread is alive. It is alive if it was initialized successfully and wasn't shutdown yet.

Returns:

true if the working thread is alive; false otherwise.

trackConnection

protected static void trackConnection(MysqlConnection conn,
                                      NetworkResources io)

Tracks the finalization of a MysqlConnection object and keeps a reference to its NetworkResources so that they can be later released.

Parameters:

conn - the Connection object to track for finalization

io - the network resources to close on the connection finalization

finalizeResource

private static void finalizeResource(AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference reference)

Release resources from the given AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference and remove it from the references set.

Parameters:

reference - the AbandonedConnectionCleanupThread.ConnectionFinalizerPhantomReference to finalize.