001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.client;
019
020import java.io.IOException;
021import java.io.InterruptedIOException;
022import java.util.ArrayDeque;
023import java.util.Queue;
024import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
025import org.apache.yetus.audience.InterfaceAudience;
026
027import org.apache.hbase.thirdparty.com.google.common.base.Throwables;
028
029/**
030 * A ResultScanner which will only send request to RS when there are no cached results when calling
031 * next, just like the ResultScanner in the old time. Mainly used for writing UTs, that we can
032 * control when to send request to RS. The default ResultScanner implementation will fetch in
033 * background.
034 */
035@InterfaceAudience.Private
036public class ScanPerNextResultScanner implements ResultScanner, AdvancedScanResultConsumer {
037
038  private final AsyncTable<AdvancedScanResultConsumer> table;
039
040  private final Scan scan;
041
042  private final Queue<Result> queue = new ArrayDeque<>();
043
044  private ScanMetrics scanMetrics;
045
046  private boolean closed = false;
047
048  private Throwable error;
049
050  private ScanResumer resumer;
051
052  public ScanPerNextResultScanner(AsyncTable<AdvancedScanResultConsumer> table, Scan scan) {
053    this.table = table;
054    this.scan = scan;
055  }
056
057  @Override
058  public synchronized void onError(Throwable error) {
059    this.error = error;
060    notifyAll();
061  }
062
063  @Override
064  public synchronized void onComplete() {
065    closed = true;
066    notifyAll();
067  }
068
069  @Override
070  public void onScanMetricsCreated(ScanMetrics scanMetrics) {
071    this.scanMetrics = scanMetrics;
072  }
073
074  @Override
075  public synchronized void onNext(Result[] results, ScanController controller) {
076    assert results.length > 0;
077    if (closed) {
078      controller.terminate();
079      return;
080    }
081    for (Result result : results) {
082      queue.add(result);
083    }
084    notifyAll();
085    resumer = controller.suspend();
086  }
087
088  @Override
089  public synchronized void onHeartbeat(ScanController controller) {
090    if (closed) {
091      controller.terminate();
092      return;
093    }
094    if (scan.isNeedCursorResult()) {
095      controller.cursor().ifPresent(c -> queue.add(Result.createCursorResult(c)));
096    }
097  }
098
099  @Override
100  public synchronized Result next() throws IOException {
101    if (queue.isEmpty()) {
102      if (resumer != null) {
103        resumer.resume();
104        resumer = null;
105      } else {
106        table.scan(scan, this);
107      }
108    }
109    while (queue.isEmpty()) {
110      if (closed) {
111        return null;
112      }
113      if (error != null) {
114        Throwables.propagateIfPossible(error, IOException.class);
115        throw new IOException(error);
116      }
117      try {
118        wait();
119      } catch (InterruptedException e) {
120        throw new InterruptedIOException();
121      }
122    }
123    return queue.poll();
124  }
125
126  @Override
127  public synchronized void close() {
128    closed = true;
129    queue.clear();
130    if (resumer != null) {
131      resumer.resume();
132      resumer = null;
133    }
134    notifyAll();
135  }
136
137  @Override
138  public boolean renewLease() {
139    // The renew lease operation will be handled in background
140    return false;
141  }
142
143  @Override
144  public ScanMetrics getScanMetrics() {
145    return scanMetrics;
146  }
147}