/*
* Copyright (c) 2018-Present Pivotal Software Inc, All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package reactor.pool;
import java.io.Closeable;
import java.io.IOException;
import java.time.Clock;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.function.Function;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Disposable;
import reactor.core.Disposables;
import reactor.core.Scannable;
import reactor.core.publisher.Mono;
import reactor.core.publisher.Operators;
import reactor.core.scheduler.Schedulers;
import reactor.util.Logger;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
import static reactor.pool.AbstractPool.AbstractPooledRef.STATE_INVALIDATED;
/**
* An abstract base version of a {@link Pool}, mutualizing small amounts of code and allowing to build common
* related classes like {@link AbstractPooledRef} or {@link Borrower}.
*
* @author Simon Baslé
*/
abstract class AbstractPool<POOLABLE> implements InstrumentedPool<POOLABLE>,
InstrumentedPool.PoolMetrics {
//A pool should be rare enough that having instance loggers should be ok
//This helps with testability of some methods that for now mainly log
final Logger logger;
final PoolConfig<POOLABLE> poolConfig;
final PoolMetricsRecorder metricsRecorder;
final Clock clock;
volatile int pendingCount;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<AbstractPool> PENDING_COUNT = AtomicIntegerFieldUpdater.newUpdater(AbstractPool.class, "pendingCount");
AbstractPool(PoolConfig<POOLABLE> poolConfig, Logger logger) {
this.poolConfig = poolConfig;
this.logger = logger;
this.metricsRecorder = poolConfig.metricsRecorder();
this.clock = poolConfig.clock();
}
// == pool introspection methods ==
@Override
public PoolMetrics metrics() {
return this;
}
@Override
public int pendingAcquireSize() {
return PENDING_COUNT.get(this);
}
@Override
public int allocatedSize() {
return poolConfig.allocationStrategy().permitGranted();
}
@Override
abstract public int idleSize();
@Override
public int acquiredSize() {
return allocatedSize() - idleSize();
}
@Override
public int getMaxAllocatedSize() {
return poolConfig.allocationStrategy().permitMaximum();
}
@Override
public int getMaxPendingAcquireSize() {
return poolConfig.maxPending() < 0 ? Integer.MAX_VALUE : poolConfig.maxPending();
}
// == common methods to interact with idle/pending queues ==
abstract boolean elementOffer(POOLABLE element);
/**
* Note to implementors: stop the {@link Borrower} countdown by calling
* {@link Borrower#stopPendingCountdown()} as soon as it is known that a resource is
* available or is in the process of being allocated.
*/
abstract void doAcquire(Borrower<POOLABLE> borrower);
abstract void cancelAcquire(Borrower<POOLABLE> borrower);
private void defaultDestroy(@Nullable POOLABLE poolable) {
if (poolable instanceof Disposable) {
((Disposable) poolable).dispose();
}
else if (poolable instanceof Closeable) {
try {
((Closeable) poolable).close();
} catch (IOException e) {
logger.trace("Failure while discarding a released Poolable that is Closeable, could not close", e);
}
}
//TODO anything else to throw away the Poolable?
}
/**
* Apply the configured destroyHandler to get the destroy {@link Mono} AND return a permit to the {@link AllocationStrategy},
* which assumes that the {@link Mono} will always be subscribed immediately.
* <p>
* Calls to this method MUST be guarded by {@link AbstractPooledRef#markInvalidate()}.
*
* @param ref the {@link PooledRef} that is not part of the live set
* @return the destroy {@link Mono}, which MUST be subscribed immediately
*/
Mono<Void> destroyPoolable(AbstractPooledRef<POOLABLE> ref) {
if (ref.state != STATE_INVALIDATED) {
throw new IllegalStateException("destroying non invalidated ref " + ref);
}
POOLABLE poolable = ref.poolable();
poolConfig.allocationStrategy().returnPermits(1);
long start = clock.millis();
metricsRecorder.recordLifetimeDuration(ref.lifeTime());
Function<POOLABLE, ? extends Publisher<Void>> factory = poolConfig.destroyHandler();
if (factory == PoolBuilder.NOOP_HANDLER) {
return Mono.fromRunnable(() -> {
defaultDestroy(poolable);
metricsRecorder.recordDestroyLatency(clock.millis() - start);
});
}
else {
return Mono.from(factory.apply(poolable))
.doFinally(fin -> metricsRecorder.recordDestroyLatency(clock.millis() - start));
}
}
/**
* An abstract base for most common statistics operator of {@link PooledRef}.
*
* @author Simon Baslé
*/
abstract static class AbstractPooledRef<T> implements PooledRef<T>, PooledRefMetadata {
final long creationTimestamp;
final PoolMetricsRecorder metricsRecorder;
final Clock clock;
final T poolable;
final int acquireCount;
long timeSinceRelease;
volatile int state;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<AbstractPooledRef> STATE = AtomicIntegerFieldUpdater.newUpdater(AbstractPooledRef.class, "state");
/**
* Use this constructor the first time a resource is created and wrapped in a {@link PooledRef}.
* @param poolable the newly created poolable
* @param metricsRecorder the recorder to use for metrics
* @param clock the {@link Clock} to use for timestamps
*/
AbstractPooledRef(T poolable, PoolMetricsRecorder metricsRecorder, Clock clock) {
this.poolable = poolable;
this.metricsRecorder = metricsRecorder;
this.clock = clock;
this.creationTimestamp = clock.millis();
this.acquireCount = 0;
this.timeSinceRelease = -2L;
this.state = STATE_IDLE;
}
/**
* Use this constructor when a resource is passed to another borrower.
*/
AbstractPooledRef(AbstractPooledRef<T> oldRef) {
this.poolable = oldRef.poolable;
this.metricsRecorder = oldRef.metricsRecorder;
this.clock = oldRef.clock;
this.creationTimestamp = oldRef.creationTimestamp;
this.acquireCount = oldRef.acquireCount(); //important to use method since the count variable is final
this.timeSinceRelease = oldRef.timeSinceRelease; //important to carry over the markReleased for metrics
//we're dealing with a new slot that was created when the previous one was released
this.state = oldRef.state == STATE_INVALIDATED ?
STATE_INVALIDATED :
STATE_IDLE;
}
@Override
public T poolable() {
return poolable;
}
@Override
public PooledRefMetadata metadata() {
return this;
}
void markAcquired() {
if (STATE.compareAndSet(this, STATE_IDLE, STATE_ACQUIRED)) {
long tsr = timeSinceRelease;
if (tsr > 0) {
metricsRecorder.recordIdleTime(clock.millis() - tsr);
}
else {
metricsRecorder.recordIdleTime(clock.millis() - creationTimestamp);
}
}
}
boolean markReleased() {
for(;;) {
int s = state;
if (s == STATE_RELEASED || s == STATE_INVALIDATED) {
return false;
}
else if (STATE.compareAndSet(this, s, STATE_RELEASED)) {
this.timeSinceRelease = clock.millis();
return true;
}
}
}
boolean markInvalidate() {
for(;;) {
int s = state;
if (s == STATE_INVALIDATED) {
return false;
}
else if (STATE.compareAndSet(this, s, STATE_INVALIDATED)) {
return true;
}
}
}
@Override
public int acquireCount() {
if (STATE.get(this) == STATE_IDLE) {
return this.acquireCount;
}
return this.acquireCount + 1;
}
@Override
public long lifeTime() {
return clock.millis() - creationTimestamp;
}
@Override
public long idleTime() {
if (STATE.get(this) == STATE_ACQUIRED) {
return 0L;
}
long tsr = this.timeSinceRelease;
if (tsr < 0L) tsr = creationTimestamp; //any negative date other than -1 is considered "never yet released"
return clock.millis() - tsr;
}
/**
* Implementors MUST have the Mono call {@link #markReleased()} upon subscription.
* <p>
* {@inheritDoc}
*/
@Override
public abstract Mono<Void> release();
/**
* Implementors MUST have the Mono call {@link #markInvalidate()} upon subscription.
* <p>
* {@inheritDoc}
*/
@Override
public abstract Mono<Void> invalidate();
@Override
public String toString() {
return "PooledRef{" +
"poolable=" + poolable +
", lifeTime=" + lifeTime() + "ms" +
", idleTime=" + idleTime() + "ms" +
", acquireCount=" + acquireCount +
'}';
}
static final int STATE_IDLE = 0;
static final int STATE_ACQUIRED = 1;
static final int STATE_RELEASED = 2;
//destroyed or in the process of being destroyed
static final int STATE_INVALIDATED = 3;
}
/**
* Common inner {@link Subscription} to be used to deliver poolable elements wrapped in {@link AbstractPooledRef} from
* an {@link AbstractPool}.
*
* @author Simon Baslé
*/
static final class Borrower<POOLABLE> extends AtomicBoolean implements Scannable, Subscription, Runnable {
static final Disposable TIMEOUT_DISPOSED = Disposables.disposed();
final CoreSubscriber<? super AbstractPooledRef<POOLABLE>> actual;
final AbstractPool<POOLABLE> pool;
final Duration acquireTimeout;
Disposable timeoutTask;
Borrower(CoreSubscriber<? super AbstractPooledRef<POOLABLE>> actual,
AbstractPool<POOLABLE> pool,
Duration acquireTimeout) {
this.actual = actual;
this.pool = pool;
this.acquireTimeout = acquireTimeout;
this.timeoutTask = TIMEOUT_DISPOSED;
}
@Override
public void run() {
if (Borrower.this.compareAndSet(false, true)) {
pool.cancelAcquire(Borrower.this);
actual.onError(new PoolAcquireTimeoutException(acquireTimeout));
}
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
//start the countdown
boolean noIdle = pool.idleSize() == 0;
boolean noPermits = pool.poolConfig.allocationStrategy().estimatePermitCount() == 0;
if (!acquireTimeout.isZero() && noIdle && noPermits) {
timeoutTask = Schedulers.parallel().schedule(this, acquireTimeout.toMillis(), TimeUnit.MILLISECONDS);
}
//doAcquire should interrupt the countdown if there is either an available
//resource or the pool can allocate one
pool.doAcquire(this);
}
}
/**
* Stop the countdown started when calling {@link AbstractPool#doAcquire(Borrower)}.
*/
void stopPendingCountdown() {
timeoutTask.dispose();
}
@Override
public void cancel() {
set(true);
pool.cancelAcquire(this);
stopPendingCountdown();
}
@Override
@Nullable
@SuppressWarnings("rawtypes")
public Object scanUnsafe(Attr key) {
if (key == Attr.CANCELLED) return get();
if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return 1;
if (key == Attr.ACTUAL) return actual;
return null;
}
void deliver(AbstractPooledRef<POOLABLE> poolSlot) {
stopPendingCountdown();
if (get()) {
//CANCELLED
poolSlot.release().subscribe(aVoid -> {}, e -> Operators.onErrorDropped(e, Context.empty())); //actual mustn't receive onError
}
else {
poolSlot.markAcquired();
actual.onNext(poolSlot);
actual.onComplete();
}
}
void fail(Throwable error) {
stopPendingCountdown();
if (!get()) {
actual.onError(error);
}
}
@Override
public String toString() {
return get() ? "Borrower(cancelled)" : "Borrower";
}
}
}
