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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hadoop.hbase.client;
import static org.apache.hadoop.hbase.client.ConnectionUtils.calcEstimatedSize;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Consumer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.yetus.audience.InterfaceAudience;
/**
* ClientAsyncPrefetchScanner implements async scanner behaviour. Specifically, the cache used by
* this scanner is a concurrent queue which allows both the producer (hbase client) and consumer
* (application) to access the queue in parallel. The number of rows returned in a prefetch is
* defined by the caching factor and the result size factor. This class allocates a buffer cache,
* whose size is a function of both factors. The prefetch is invoked when the cache is half-filled,
* instead of waiting for it to be empty. This is defined in the method
* {@link ClientAsyncPrefetchScanner#prefetchCondition()}.
*/
@InterfaceAudience.Private
public class ClientAsyncPrefetchScanner extends ClientSimpleScanner {
private long maxCacheSize;
private AtomicLong cacheSizeInBytes;
// exception queue (from prefetch to main scan execution)
private final Queue exceptionsQueue;
// used for testing
private Consumer prefetchListener;
private final Lock lock = new ReentrantLock();
private final Condition notEmpty = lock.newCondition();
private final Condition notFull = lock.newCondition();
public ClientAsyncPrefetchScanner(Configuration configuration, Scan scan, Scan scanForMetrics,
TableName name, ClusterConnection connection, RpcRetryingCallerFactory rpcCallerFactory,
RpcControllerFactory rpcControllerFactory, ExecutorService pool, int scanReadRpcTimeout,
int scannerTimeout, int replicaCallTimeoutMicroSecondScan,
ConnectionConfiguration connectionConfiguration, Map requestAttributes)
throws IOException {
super(configuration, scan, scanForMetrics, name, connection, rpcCallerFactory,
rpcControllerFactory, pool, scanReadRpcTimeout, scannerTimeout,
replicaCallTimeoutMicroSecondScan, connectionConfiguration, requestAttributes);
exceptionsQueue = new ConcurrentLinkedQueue<>();
final Context context = Context.current();
final Runnable runnable = context.wrap(new PrefetchRunnable());
Threads.setDaemonThreadRunning(new Thread(runnable), name + ".asyncPrefetcher");
}
void setPrefetchListener(Consumer prefetchListener) {
this.prefetchListener = prefetchListener;
}
@Override
protected void initCache() {
// Override to put a different cache in place of the super's -- a concurrent one.
cache = new LinkedBlockingQueue<>();
maxCacheSize = resultSize2CacheSize(maxScannerResultSize);
cacheSizeInBytes = new AtomicLong(0);
}
private long resultSize2CacheSize(long maxResultSize) {
// * 2 if possible
return maxResultSize > Long.MAX_VALUE / 2 ? maxResultSize : maxResultSize * 2;
}
@Override
public Result next() throws IOException {
try (Scope ignored = span.makeCurrent()) {
lock.lock();
try {
while (cache.isEmpty()) {
handleException();
if (this.closed) {
return null;
}
try {
notEmpty.await();
} catch (InterruptedException e) {
span.recordException(e);
throw new InterruptedIOException("Interrupted when wait to load cache");
}
}
Result result = pollCache();
if (prefetchCondition()) {
notFull.signalAll();
}
return result;
} finally {
lock.unlock();
handleException();
}
}
}
@Override
public void close() {
lock.lock();
try {
super.close();
closed = true;
notFull.signalAll();
notEmpty.signalAll();
} finally {
lock.unlock();
}
}
@Override
protected void addEstimatedSize(long estimatedSize) {
cacheSizeInBytes.addAndGet(estimatedSize);
}
private void handleException() throws IOException {
// The prefetch task running in the background puts any exception it
// catches into this exception queue.
// Rethrow the exception so the application can handle it.
while (!exceptionsQueue.isEmpty()) {
Exception first = exceptionsQueue.peek();
first.printStackTrace();
if (first instanceof IOException) {
throw (IOException) first;
}
throw (RuntimeException) first;
}
}
private boolean prefetchCondition() {
return cacheSizeInBytes.get() < maxCacheSize / 2;
}
private Result pollCache() {
Result res = cache.poll();
long estimatedSize = calcEstimatedSize(res);
addEstimatedSize(-estimatedSize);
return res;
}
private class PrefetchRunnable implements Runnable {
@Override
public void run() {
while (!closed) {
boolean succeed = false;
try {
lock.lock();
while (!prefetchCondition()) {
notFull.await();
}
loadCache();
succeed = true;
} catch (Exception e) {
exceptionsQueue.add(e);
span.recordException(e);
} finally {
notEmpty.signalAll();
lock.unlock();
if (prefetchListener != null) {
prefetchListener.accept(succeed);
}
}
}
}
}
}
