org.apache.hadoop.hbase.client

Class AsyncClientScanner

java.lang.Object

org.apache.hadoop.hbase.client.AsyncClientScanner

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, AsyncResultScanner

Direct Known Subclasses:

AsyncClientSmallScanner, AsyncReversedClientScanner

@InterfaceAudience.Public
@InterfaceStability.Stable
public class AsyncClientScanner
extends java.lang.Object
implements AsyncResultScanner

Implements the scanner interface for the HBase client. If there are multiple regions in a table, this scanner will iterate through them all.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	caching
protected AsyncScannerCallable	callable
protected AsyncRpcRetryingCaller<org.apache.hadoop.hbase.client.Result[]>	caller
protected boolean	closed
protected org.apache.hadoop.hbase.HRegionInfo	currentRegion
protected long	lastNext
protected org.apache.hadoop.hbase.client.Result	lastResult
protected long	maxScannerResultSize
protected org.apache.hadoop.hbase.client.Scan	scan
protected org.apache.hadoop.hbase.client.metrics.ScanMetrics	scanMetrics
protected boolean	scanMetricsPublished
protected int	scannerTimeout

Constructor Summary

Constructors

Constructor and Description
AsyncClientScanner(AsyncRpcClient client, org.apache.hadoop.hbase.client.Scan scan, org.apache.hadoop.hbase.TableName tableName) Create a new ClientScanner for the specified table Note that the passed Scan's start row maybe changed changed.

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	checkScanStopRow(byte[] endKey)
void	close()
protected org.apache.hadoop.hbase.client.Scan	getScan()
protected org.apache.hadoop.hbase.client.metrics.ScanMetrics	getScanMetrics()
protected AsyncScannerCallable	getScannerCallable(byte[] localStartKey, int nbRows) Get the callable for the scan
protected org.apache.hadoop.hbase.TableName	getTable()
protected long	getTimestamp()
protected void	initScanMetrics(org.apache.hadoop.hbase.client.Scan scan) Check and initialize if application wants to collect scan metrics
boolean	isScanDone() Check if the scanner is done
<H extends ResponseHandler<org.apache.hadoop.hbase.client.Result[]>> H	nextBatch(H handler) Get the default number of rows as set by "hbase.client.scanner.caching"
protected void	nextScanner(int nbRows, boolean done, ResponseHandler<java.lang.Boolean> handler) Gets a scanner for the next region.
protected void	setScanDone() Set the scanner as done
protected void	writeScanMetrics() Publish the scan metrics.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

scan

protected org.apache.hadoop.hbase.client.Scan scan

closed

protected boolean closed

currentRegion

protected org.apache.hadoop.hbase.HRegionInfo currentRegion

callable

protected AsyncScannerCallable callable

caching

protected final int caching

lastNext

protected long lastNext

lastResult

protected org.apache.hadoop.hbase.client.Result lastResult

maxScannerResultSize

protected final long maxScannerResultSize

scannerTimeout

protected final int scannerTimeout

scanMetricsPublished

protected boolean scanMetricsPublished

caller

protected AsyncRpcRetryingCaller<org.apache.hadoop.hbase.client.Result[]> caller

scanMetrics

protected org.apache.hadoop.hbase.client.metrics.ScanMetrics scanMetrics

Constructor Detail

AsyncClientScanner

public AsyncClientScanner(AsyncRpcClient client,
                  org.apache.hadoop.hbase.client.Scan scan,
                  org.apache.hadoop.hbase.TableName tableName)

Create a new ClientScanner for the specified table Note that the passed Scan's start row maybe changed changed.

Parameters:

client - The AsyncRpcClient to use.

scan - Scan to use in this scanner

tableName - The table that we wish to scan

Method Detail

initScanMetrics

protected void initScanMetrics(org.apache.hadoop.hbase.client.Scan scan)

Check and initialize if application wants to collect scan metrics

Parameters:

scan - to init it for

getScanMetrics

protected org.apache.hadoop.hbase.client.metrics.ScanMetrics getScanMetrics()

Returns:

scan metrics

getTable

protected org.apache.hadoop.hbase.TableName getTable()

Returns:

TableName

getScan

protected org.apache.hadoop.hbase.client.Scan getScan()

Returns:

the used Scan

getTimestamp

protected long getTimestamp()

Returns:

last timestamp

checkScanStopRow

protected boolean checkScanStopRow(byte[] endKey)

Parameters:

endKey - to check

Returns:

returns true if the passed region endKey

nextScanner

protected void nextScanner(int nbRows,
               boolean done,
               ResponseHandler<java.lang.Boolean> handler)

Gets a scanner for the next region. If this.currentRegion != null, then we will move to the endrow of this.currentRegion. Else we will get scanner at the scan.getStartRow(). We will go no further, just tidy up outstanding scanners, if currentRegion != null and done is true.

Parameters:

nbRows - number of rows to scan

done - Server-side says we're done scanning.

handler - for the next scanner

getScannerCallable

@InterfaceAudience.Private
protected AsyncScannerCallable getScannerCallable(byte[] localStartKey,
                                                                int nbRows)

Get the callable for the scan

Parameters:

localStartKey - start key for the scan

nbRows - number of rows

Returns:

async scanner

writeScanMetrics

protected void writeScanMetrics()

Publish the scan metrics. For now, we use scan.setAttribute to pass the metrics back to the application or TableInputFormat.Later, we could push it to other systems. We don't use metrics framework because it doesn't support multi-instances of the same metrics on the same machine; for scan/map reduce scenarios, we will have multiple scans running at the same time.

By default, scan metrics are disabled; if the application wants to collect them, this behavior can be turned on by calling calling:

scan.setAttribute(SCAN_ATTRIBUTES_METRICS_ENABLE, Bytes.toBytes(Boolean.TRUE))

nextBatch

public <H extends ResponseHandler<org.apache.hadoop.hbase.client.Result[]>> H nextBatch(H handler)

Description copied from interface: AsyncResultScanner

Get the default number of rows as set by "hbase.client.scanner.caching"

Specified by:

nextBatch in interface AsyncResultScanner

Parameters:

handler - to handle responses

Returns:

Between zero and nbRows Results

isScanDone

public boolean isScanDone()

Description copied from interface: AsyncResultScanner

Check if the scanner is done

Specified by:

isScanDone in interface AsyncResultScanner

Returns:

true if the scanner is done scanning all rows

setScanDone

protected void setScanDone()

Set the scanner as done

close

public void close()

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable