/**
* Copyright The Apache Software Foundation
*
* 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 org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
import org.apache.hadoop.hbase.util.Bytes;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
/**
* Client scanner for small reversed scan. Generally, only one RPC is called to fetch the
* scan results, unless the results cross multiple regions or the row count of
* results exceed the caching.
* <p/>
* For small scan, it will get better performance than {@link ReversedClientScanner}
*/
@InterfaceAudience.Private
public class ClientSmallReversedScanner extends ReversedClientScanner {
private static final Log LOG = LogFactory.getLog(ClientSmallReversedScanner.class);
private ScannerCallableWithReplicas smallScanCallable = null;
private byte[] skipRowOfFirstResult = null;
/**
* Create a new ReversibleClientScanner for the specified table Note that the
* passed {@link Scan}'s start row maybe changed changed.
*
* @param conf The {@link Configuration} to use.
* @param scan {@link Scan} to use in this scanner
* @param tableName The table that we wish to rangeGet
* @param connection Connection identifying the cluster
* @param rpcFactory
* @throws IOException
*/
public ClientSmallReversedScanner(final Configuration conf, final Scan scan,
final TableName tableName, ClusterConnection connection,
RpcRetryingCallerFactory rpcFactory, RpcControllerFactory controllerFactory,
ExecutorService pool, int primaryOperationTimeout) throws IOException {
super(conf, scan, tableName, connection, rpcFactory, controllerFactory, pool, primaryOperationTimeout);
}
/**
* Gets a scanner for following scan. Move to next region or continue from the
* last result or start from the start row.
*
* @param nbRows
* @param done true if Server-side says we're done scanning.
* @param currentRegionDone true if scan is over on current region
* @return true if has next scanner
* @throws IOException
*/
private boolean nextScanner(int nbRows, final boolean done,
boolean currentRegionDone) throws IOException {
// Where to start the next getter
byte[] localStartKey;
int cacheNum = nbRows;
skipRowOfFirstResult = null;
// if we're at end of table, close and return false to stop iterating
if (this.currentRegion != null && currentRegionDone) {
byte[] startKey = this.currentRegion.getStartKey();
if (startKey == null
|| Bytes.equals(startKey, HConstants.EMPTY_BYTE_ARRAY)
|| checkScanStopRow(startKey) || done) {
close();
if (LOG.isDebugEnabled()) {
LOG.debug("Finished with small scan at " + this.currentRegion);
}
return false;
}
// We take the row just under to get to the previous region.
localStartKey = createClosestRowBefore(startKey);
if (LOG.isDebugEnabled()) {
LOG.debug("Finished with region " + this.currentRegion);
}
} else if (this.lastResult != null) {
localStartKey = this.lastResult.getRow();
skipRowOfFirstResult = this.lastResult.getRow();
cacheNum++;
} else {
localStartKey = this.scan.getStartRow();
}
if (LOG.isTraceEnabled()) {
LOG.trace("Advancing internal small scanner to startKey at '"
+ Bytes.toStringBinary(localStartKey) + "'");
}
smallScanCallable = ClientSmallScanner.getSmallScanCallable(
getConnection(), getTable(), scan, getScanMetrics(), localStartKey, cacheNum,
rpcControllerFactory, getPool(), getPrimaryOperationTimeout(),
getRetries(), getScannerTimeout(), getConf(), caller);
if (this.scanMetrics != null && skipRowOfFirstResult == null) {
this.scanMetrics.countOfRegions.incrementAndGet();
}
return true;
}
@Override
public Result next() throws IOException {
// If the scanner is closed and there's nothing left in the cache, next is a
// no-op.
if (cache.size() == 0 && this.closed) {
return null;
}
if (cache.size() == 0) {
Result[] values = null;
long remainingResultSize = maxScannerResultSize;
int countdown = this.caching;
boolean currentRegionDone = false;
// Values == null means server-side filter has determined we must STOP
while (remainingResultSize > 0 && countdown > 0
&& nextScanner(countdown, values == null, currentRegionDone)) {
// Server returns a null values if scanning is to stop. Else,
// returns an empty array if scanning is to go on and we've just
// exhausted current region.
// callWithoutRetries is at this layer. Within the ScannerCallableWithReplicas,
// we do a callWithRetries
values = this.caller.callWithoutRetries(smallScanCallable, scannerTimeout);
this.currentRegion = smallScanCallable.getHRegionInfo();
long currentTime = System.currentTimeMillis();
if (this.scanMetrics != null) {
this.scanMetrics.sumOfMillisSecBetweenNexts.addAndGet(currentTime
- lastNext);
}
lastNext = currentTime;
if (values != null && values.length > 0) {
for (int i = 0; i < values.length; i++) {
Result rs = values[i];
if (i == 0 && this.skipRowOfFirstResult != null
&& Bytes.equals(skipRowOfFirstResult, rs.getRow())) {
// Skip the first result
continue;
}
cache.add(rs);
// We don't make Iterator here
for (Cell cell : rs.rawCells()) {
remainingResultSize -= CellUtil.estimatedHeapSizeOf(cell);
}
countdown--;
this.lastResult = rs;
}
}
currentRegionDone = countdown > 0;
}
}
if (cache.size() > 0) {
return cache.poll();
}
// if we exhausted this scanner before calling close, write out the scan
// metrics
writeScanMetrics();
return null;
}
@Override
protected void initializeScannerInConstruction() throws IOException {
// No need to initialize the scanner when constructing instance, do it when
// calling next(). Do nothing here.
}
@Override
public void close() {
if (!scanMetricsPublished) writeScanMetrics();
closed = true;
}
}