/
Waiter.java
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/
Waiter.java
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/*
* Copyright 2016 Google LLC
*
* 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
*
* http://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 com.google.cloud.bigquery.storage.v1alpha2;
import com.google.api.core.InternalApi;
import com.google.api.gax.batching.FlowControlSettings;
import com.google.api.gax.batching.FlowController;
import java.util.LinkedList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Logger;
/**
* A barrier kind of object that helps keep track of pending actions and synchronously wait until
* all have completed.
*/
class Waiter {
private static final Logger LOG = Logger.getLogger(Waiter.class.getName());
private long pendingCount;
private long pendingSize;
private long countLimit;
private long sizeLimit;
private FlowController.LimitExceededBehavior behavior;
private LinkedList<CountDownLatch> awaitingMessageAcquires;
private LinkedList<CountDownLatch> awaitingBytesAcquires;
private final Lock lock;
Waiter(FlowControlSettings flowControlSettings) {
pendingCount = 0;
pendingSize = 0;
this.awaitingMessageAcquires = new LinkedList<CountDownLatch>();
this.awaitingBytesAcquires = new LinkedList<CountDownLatch>();
this.countLimit = flowControlSettings.getMaxOutstandingElementCount();
this.sizeLimit = flowControlSettings.getMaxOutstandingRequestBytes();
this.behavior = flowControlSettings.getLimitExceededBehavior();
this.lock = new ReentrantLock();
}
private void notifyNextAcquires() {
if (!awaitingMessageAcquires.isEmpty()) {
CountDownLatch awaitingAcquire = awaitingMessageAcquires.getFirst();
awaitingAcquire.countDown();
}
if (!awaitingBytesAcquires.isEmpty()) {
CountDownLatch awaitingAcquire = awaitingBytesAcquires.getFirst();
awaitingAcquire.countDown();
}
}
public synchronized void release(long messageSize) {
lock.lock();
--pendingCount;
pendingSize -= messageSize;
notifyNextAcquires();
lock.unlock();
notifyAll();
}
public void acquire(long messageSize) throws FlowController.FlowControlException {
lock.lock();
try {
if (pendingCount >= countLimit
&& behavior == FlowController.LimitExceededBehavior.ThrowException) {
throw new FlowController.MaxOutstandingElementCountReachedException(countLimit);
}
if (pendingSize + messageSize >= sizeLimit
&& behavior == FlowController.LimitExceededBehavior.ThrowException) {
throw new FlowController.MaxOutstandingRequestBytesReachedException(sizeLimit);
}
CountDownLatch messageWaiter = null;
while (pendingCount >= countLimit) {
if (messageWaiter == null) {
messageWaiter = new CountDownLatch(1);
awaitingMessageAcquires.addLast(messageWaiter);
} else {
// This message already in line stays at the head of the line.
messageWaiter = new CountDownLatch(1);
awaitingMessageAcquires.set(0, messageWaiter);
}
lock.unlock();
try {
messageWaiter.await();
} catch (InterruptedException e) {
LOG.warning("Interrupted while waiting to acquire flow control tokens");
}
lock.lock();
}
++pendingCount;
if (messageWaiter != null) {
awaitingMessageAcquires.removeFirst();
}
if (!awaitingMessageAcquires.isEmpty() && pendingCount < countLimit) {
awaitingMessageAcquires.getFirst().countDown();
}
// Now acquire space for bytes.
CountDownLatch bytesWaiter = null;
Long bytesRemaining = messageSize;
while (pendingSize + messageSize >= sizeLimit) {
if (bytesWaiter == null) {
// This message gets added to the back of the line.
bytesWaiter = new CountDownLatch(1);
awaitingBytesAcquires.addLast(bytesWaiter);
} else {
// This message already in line stays at the head of the line.
bytesWaiter = new CountDownLatch(1);
awaitingBytesAcquires.set(0, bytesWaiter);
}
lock.unlock();
try {
bytesWaiter.await();
} catch (InterruptedException e) {
LOG.warning("Interrupted while waiting to acquire flow control tokens");
}
lock.lock();
}
pendingSize += messageSize;
if (bytesWaiter != null) {
awaitingBytesAcquires.removeFirst();
}
// There may be some surplus bytes left; let the next message waiting for bytes have some.
if (!awaitingBytesAcquires.isEmpty() && pendingSize < sizeLimit) {
awaitingBytesAcquires.getFirst().countDown();
}
} finally {
lock.unlock();
}
}
public synchronized void waitComplete(long timeoutMillis) throws InterruptedException {
long end = System.currentTimeMillis() + timeoutMillis;
lock.lock();
try {
while (pendingCount > 0 && (timeoutMillis == 0 || end > System.currentTimeMillis())) {
lock.unlock();
try {
wait(timeoutMillis == 0 ? 0 : end - System.currentTimeMillis());
} catch (InterruptedException e) {
throw e;
}
lock.lock();
}
if (pendingCount > 0) {
throw new InterruptedException("Wait timeout");
}
} finally {
lock.unlock();
}
}
@InternalApi
public long pendingCount() {
return pendingCount;
}
@InternalApi
public long pendingSize() {
return pendingSize;
}
}