org.eclipse.persistence.sessions.server.ReadConnectionPool Maven / Gradle / Ivy
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/*
* Copyright (c) 1998, 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Oracle - initial API and implementation from Oracle TopLink
package org.eclipse.persistence.sessions.server;
import org.eclipse.persistence.internal.databaseaccess.*;
import org.eclipse.persistence.logging.SessionLog;
import org.eclipse.persistence.sessions.Login;
import org.eclipse.persistence.exceptions.*;
/**
*
* Purpose: The read connection pool is used for read access through the server session.
* Any of the connection pools can be used for the read pool however this is the default.
* This pool allows for concurrent reads against the same JDBC connection and requires that
* the JDBC connection support concurrent read access.
*/
public class ReadConnectionPool extends ConnectionPool {
/**
* PUBLIC:
* Build a new read connection pool.
*/
public ReadConnectionPool() {
super();
}
/**
* PUBLIC:
* Build a new read connection pool.
*/
public ReadConnectionPool(String name, Login login, ServerSession owner) {
super(name, login, owner);
}
/**
* PUBLIC:
* Build a new read connection pool.
*/
public ReadConnectionPool(String name, Login login, int minNumberOfConnections, int maxNumberOfConnections, ServerSession owner) {
super(name, login, minNumberOfConnections, maxNumberOfConnections, owner);
}
/**
* PUBLIC:
* Build a new read connection pool.
*/
public ReadConnectionPool(String name, Login login, int initialNumberOfConnections, int minNumberOfConnections, int maxNumberOfConnections, ServerSession owner) {
super(name, login, initialNumberOfConnections, minNumberOfConnections, maxNumberOfConnections, owner);
}
/**
* INTERNAL:
* Wait until a connection is available and allocate the connection for the client.
*/
@Override
public synchronized Accessor acquireConnection() throws ConcurrencyException {
// Check for dead database and fail-over.
if (this.isDead) {
return failover();
}
Accessor leastBusyConnection = null;
// Search for an unused connection, also find the least busy in case all are used.
int size = this.connectionsAvailable.size();
for (int index = 0; index < size; index++) {
Accessor connection = this.connectionsAvailable.get(index);
//if the pool has encountered a connection failure on one of the accessors lets test the others.
if (this.checkConnections){
if (this.owner.getLogin().isConnectionHealthValidatedOnError() && this.owner.getServerPlatform().wasFailureCommunicationBased(null, connection, this.owner)){
this.connectionsAvailable.remove(index);
try {
//connection failed connect test
connection.closeConnection();
} catch (Exception ex){
//ignore
} finally {
connection.releaseCustomizer();
}
//reset index as we just removed a connection and should check at the same index again
--index;
//reset size as there are one less connection in the pool now.
--size;
continue; //skip back to beginning of loop
} else {
this.checkConnections = false;
}
}
if (connection.getCallCount() == 0) {
leastBusyConnection = connection;
break;
}
if ((leastBusyConnection == null) || (leastBusyConnection.getCallCount() > connection.getCallCount())) {
leastBusyConnection = connection;
}
}
// If still not at max, add a new connection.
if (((leastBusyConnection == null) || (leastBusyConnection.getCallCount() != 0))
&& (this.connectionsAvailable.size() + this.connectionsUsed.size()) < this.maxNumberOfConnections) {
Accessor connection = null;
try {
connection = buildConnection();
} catch (RuntimeException failed) {
if (!this.failoverConnectionPools.isEmpty()) {
this.isDead = true;
this.timeOfDeath = System.currentTimeMillis();
this.owner.logThrowable(SessionLog.WARNING, SessionLog.SQL, failed);
return acquireConnection();
} else {
throw failed;
}
}
this.connectionsAvailable.add(connection);
leastBusyConnection = connection;
}
// Use the least busy connection.
leastBusyConnection.incrementCallCount(getOwner());
if (this.owner.shouldLog(SessionLog.FINEST, SessionLog.CONNECTION)) {
Object[] args = new Object[1];
args[0] = this.name;
this.owner.log(SessionLog.FINEST, SessionLog.CONNECTION, "acquire_connection", args, leastBusyConnection);
}
return leastBusyConnection;
}
/**
* INTERNAL:
* Concurrent reads are supported.
*/
@Override
public boolean hasConnectionAvailable() {
return true;
}
/**
* INTERNAL:
* Because connections are not exclusive nothing is required.
*/
@Override
public synchronized void releaseConnection(Accessor connection) throws DatabaseException {
if (this.owner.shouldLog(SessionLog.FINEST, SessionLog.CONNECTION)) {
Object[] args = new Object[1];
args[0] = this.name;
this.owner.log(SessionLog.FINEST, SessionLog.CONNECTION, "release_connection", args, connection);
}
connection.decrementCallCount();
if (!connection.isValid()){
this.checkConnections = true;
this.connectionsAvailable.remove(connection);
try{
connection.disconnect(getOwner());
}catch (Exception ex){
//ignore
}
}
}
}