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// Portions Copyright [2021] Payara Foundation and/or affiliates
package com.sun.enterprise.resource.pool.datastructure;
import com.sun.appserv.connectors.internal.api.PoolingException;
import com.sun.enterprise.resource.ResourceHandle;
import com.sun.enterprise.resource.allocator.ResourceAllocator;
import com.sun.enterprise.resource.pool.ResourceHandler;
import com.sun.logging.LogDomains;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Supplier;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* ReadWriteLock based datastructure for pool
* @author Jagadish Ramu
*/
public class RWLockDataStructure implements DataStructure {
private final ResourceHandler handler;
private int maxSize;
private final List allResources;
private final Deque freeResources;
private final ReentrantReadWriteLock reentrantLock = new ReentrantReadWriteLock();
private final ReentrantReadWriteLock.ReadLock readLock = reentrantLock.readLock();
private final ReentrantReadWriteLock.WriteLock writeLock = reentrantLock.writeLock();
private final AtomicInteger remainingCapacity;
protected static final Logger _logger = LogDomains.getLogger(RWLockDataStructure.class,LogDomains.RSR_LOGGER);
public RWLockDataStructure(int maxSize, ResourceHandler handler) {
allResources = new ArrayList<>(Math.min(maxSize, 1000));
freeResources = new ArrayDeque<>(Math.min(maxSize, 1000));
this.maxSize = maxSize;
this.handler = handler;
this.remainingCapacity = new AtomicInteger(maxSize);
if(_logger.isLoggable(Level.FINEST)) {
_logger.log(Level.FINEST, "pool.datastructure.rwlockds.init");
}
}
/**
* {@inheritDoc}
*/
public int addResource(final ResourceAllocator allocator, int count) throws PoolingException {
int numResAdded = 0;
for (int i = 0; i < count && canGrow(); i++) {
try {
final ResourceHandle handle = handler.createResource(allocator);
doLockSecured(() -> {
allResources.add(handle);
freeResources.offerLast(handle);
}, writeLock);
numResAdded++;
} catch (Exception e) {
increaseRemainingCapacity();
throw new PoolingException(e.getMessage(), e);
}
}
return numResAdded;
}
private boolean canGrow() {
int capacity = remainingCapacity.getAndUpdate((x) -> x > 0 ? x - 1 : 0);
return capacity > 0;
}
private void increaseRemainingCapacity() {
remainingCapacity.incrementAndGet();
}
/**
* {@inheritDoc}
*/
public ResourceHandle getResource() {
return doLockSecured(() -> {
final ResourceHandle resourceHandle = freeResources.pollFirst();
if (resourceHandle != null) {
resourceHandle.setBusy(true);
}
return resourceHandle;
}, writeLock);
}
/**
* {@inheritDoc}
*/
public void removeResource(ResourceHandle resource) {
boolean removed = doLockSecured(() -> {
final boolean removedResource = allResources.remove(resource);
if (removedResource) {
freeResources.remove(resource);
increaseRemainingCapacity();
}
return removedResource;
}, writeLock);
if (removed) {
handler.deleteResource(resource);
}
}
/**
* {@inheritDoc}
*/
public void returnResource(final ResourceHandle resource) {
doLockSecured(() -> {
resource.setBusy(false);
freeResources.offerFirst(resource);
}, writeLock);
}
/**
* {@inheritDoc}
*/
public int getFreeListSize() {
return doLockSecured(freeResources::size, readLock);
}
/**
* {@inheritDoc}
*/
public void removeAll() {
final List removedResources = new ArrayList<>();
doLockSecured(() -> {
removedResources.addAll(allResources);
allResources.clear();
freeResources.clear();
remainingCapacity.set(maxSize);
}, writeLock);
for(ResourceHandle resourceHandle : removedResources) {
handler.deleteResource(resourceHandle);
}
}
/**
* {@inheritDoc}
*/
public int getResourcesSize() {
return doLockSecured(allResources::size, readLock);
}
/**
* Set maxSize based on the new max pool size set on the connection pool
* during a reconfiguration.
*
* @param maxSize
*/
public void setMaxSize(int maxSize) {
doLockSecured(() -> {
int delta = maxSize - this.maxSize;
remainingCapacity.getAndUpdate(x -> x + delta);
// remaining capacity might be negative after this, but its up to ConnectionPool to remove some of the resources
// before asking for new ones
this.maxSize = maxSize;
}, writeLock);
}
@Override
public ArrayList getAllResources() {
throw new UnsupportedOperationException("Not supported yet.");
}
private void doLockSecured(Runnable lockSecuredProc, Lock lock) {
lock.lock();
try {
lockSecuredProc.run();
} finally {
lock.unlock();
}
}
private T doLockSecured(Supplier lockSecuredFunc, Lock lock) {
lock.lock();
try {
return lockSecuredFunc.get();
} finally {
lock.unlock();
}
}
}