/**
* 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 java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedList;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.KeyValueUtil;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.ipc.PayloadCarryingRpcController;
import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.protobuf.RequestConverter;
import org.apache.hadoop.hbase.protobuf.ResponseConverter;
import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.ScanRequest;
import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.ScanResponse;
import org.apache.hadoop.hbase.util.Bytes;
import com.google.protobuf.ServiceException;
/**
* Client scanner for small scan. Generally, only one RPC is called to fetch the
* scan results, unless the results cross multiple regions or the row count of
* results excess the caching.
*
* For small scan, it will get better performance than {@link ClientScanner}
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class ClientSmallScanner extends ClientScanner {
private final Log LOG = LogFactory.getLog(this.getClass());
private RegionServerCallable<Result[]> smallScanCallable = null;
// When fetching results from server, skip the first result if it has the same
// row with this one
private byte[] skipRowOfFirstResult = null;
/**
* Create a new ClientSmallScanner for the specified table. An HConnection
* will be retrieved using the passed Configuration. Note that the passed
* {@link Scan} 's start row maybe 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
* @throws IOException
*/
public ClientSmallScanner(final Configuration conf, final Scan scan,
final TableName tableName) throws IOException {
this(conf, scan, tableName, HConnectionManager.getConnection(conf));
}
/**
* Create a new ClientSmallScanner for the specified table. An HConnection
* will be retrieved using the passed Configuration. Note that the passed
* {@link Scan} 's start row maybe changed.
* @param conf
* @param scan
* @param tableName
* @param connection
* @throws IOException
*/
public ClientSmallScanner(final Configuration conf, final Scan scan,
final TableName tableName, HConnection connection) throws IOException {
this(conf, scan, tableName, connection, new RpcRetryingCallerFactory(conf));
}
/**
* Create a new ShortClientScanner 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 ClientSmallScanner(final Configuration conf, final Scan scan,
final TableName tableName, HConnection connection,
RpcRetryingCallerFactory rpcFactory) throws IOException {
super(conf, scan, tableName, connection, rpcFactory);
}
@Override
protected void initializeScannerInConstruction() throws IOException {
// No need to initialize the scanner when constructing instance, do it when
// calling next(). Do nothing here.
}
/**
* 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[] endKey = this.currentRegion.getEndKey();
if (endKey == null || Bytes.equals(endKey, HConstants.EMPTY_BYTE_ARRAY)
|| checkScanStopRow(endKey) || done) {
close();
if (LOG.isDebugEnabled()) {
LOG.debug("Finished with small scan at " + this.currentRegion);
}
return false;
}
localStartKey = endKey;
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 = getSmallScanCallable(localStartKey, cacheNum);
if (this.scanMetrics != null && skipRowOfFirstResult == null) {
this.scanMetrics.countOfRegions.incrementAndGet();
}
return true;
}
private RegionServerCallable<Result[]> getSmallScanCallable(
byte[] localStartKey, final int cacheNum) {
this.scan.setStartRow(localStartKey);
RegionServerCallable<Result[]> callable = new RegionServerCallable<Result[]>(
getConnection(), getTable(), scan.getStartRow()) {
public Result[] call() throws IOException {
ScanRequest request = RequestConverter.buildScanRequest(getLocation()
.getRegionInfo().getRegionName(), scan, cacheNum, true);
ScanResponse response = null;
PayloadCarryingRpcController controller = new PayloadCarryingRpcController();
try {
controller.setPriority(getTableName());
response = getStub().scan(controller, request);
return ResponseConverter.getResults(controller.cellScanner(),
response);
} catch (ServiceException se) {
throw ProtobufUtil.getRemoteException(se);
}
}
};
return callable;
}
@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.
values = this.caller.callWithRetries(smallScanCallable);
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);
for (Cell kv : rs.rawCells()) {
remainingResultSize -= KeyValueUtil.ensureKeyValue(kv).heapSize();
}
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
public void close() {
if (!scanMetricsPublished) writeScanMetrics();
closed = true;
}
}