org.apache.hadoop.hbase.mapreduce

Class TableInputFormatBase

java.lang.Object

org.apache.hadoop.mapreduce.InputFormat<ImmutableBytesWritable,Result>

org.apache.hadoop.hbase.mapreduce.TableInputFormatBase

Direct Known Subclasses:

TableInputFormat

@InterfaceAudience.Public
public abstract class TableInputFormatBase
extends org.apache.hadoop.mapreduce.InputFormat<ImmutableBytesWritable,Result>

A base for TableInputFormats. Receives a Connection, a TableName, an Scan instance that defines the input columns etc. Subclasses may use other TableRecordReader implementations. Subclasses MUST ensure initializeTable(Connection, TableName) is called for an instance to function properly. Each of the entry points to this class used by the MapReduce framework, createRecordReader(InputSplit, TaskAttemptContext) and getSplits(JobContext), will call initialize(JobContext) as a convenient centralized location to handle retrieving the necessary configuration information. If your subclass overrides either of these methods, either call the parent version or call initialize yourself.

An example of a subclass:

   class ExampleTIF extends TableInputFormatBase {

      @Override
     protected void initialize(JobContext context) throws IOException {
       // We are responsible for the lifecycle of this connection until we hand it over in
       // initializeTable.
       Connection connection = ConnectionFactory.createConnection(HBaseConfiguration.create(
              job.getConfiguration()));
       TableName tableName = TableName.valueOf("exampleTable");
       // mandatory. once passed here, TableInputFormatBase will handle closing the connection.
       initializeTable(connection, tableName);
       byte[][] inputColumns = new byte [][] { Bytes.toBytes("columnA"),
         Bytes.toBytes("columnB") };
       // optional, by default we'll get everything for the table.
       Scan scan = new Scan();
       for (byte[] family : inputColumns) {
         scan.addFamily(family);
       }
       Filter exampleFilter = new RowFilter(CompareOp.EQUAL, new RegexStringComparator("aa.*"));
       scan.setFilter(exampleFilter);
       setScan(scan);
     }
   }
 

The number of InputSplits(mappers) match the number of regions in a table by default. Set "hbase.mapreduce.tableinput.mappers.per.region" to specify how many mappers per region, set this property will disable autobalance below.\ Set "hbase.mapreduce.tif.input.autobalance" to enable autobalance, hbase will assign mappers based on average region size; For regions, whose size larger than average region size may assigned more mappers, and for smaller one, they may group together to use one mapper. If actual average region size is too big, like 50G, it is not good to only assign 1 mapper for those large regions. Use "hbase.mapreduce.tif.ave.regionsize" to set max average region size when enable "autobalanece", default mas average region size is 8G.

Field Summary

Fields

Modifier and Type	Field and Description
static String	MAPREDUCE_INPUT_AUTOBALANCE Specify if we enable auto-balance to set number of mappers in M/R jobs.
static String	MAX_AVERAGE_REGION_SIZE In auto-balance, we split input by ave region size, if calculated region size is too big, we can set it.
static String	NUM_MAPPERS_PER_REGION Set the number of Mappers for each region, all regions have same number of Mappers

Constructor Summary

Constructors

Constructor and Description
TableInputFormatBase()

Method Summary

Modifier and Type	Method and Description
List<org.apache.hadoop.mapreduce.InputSplit>	calculateAutoBalancedSplits(List<org.apache.hadoop.mapreduce.InputSplit> splits, long maxAverageRegionSize) Calculates the number of MapReduce input splits for the map tasks.
protected void	closeTable() Close the Table and related objects that were initialized via initializeTable(Connection, TableName).
protected List<org.apache.hadoop.mapreduce.InputSplit>	createNInputSplitsUniform(org.apache.hadoop.mapreduce.InputSplit split, int n) Create n splits for one InputSplit, For now only support uniform distribution
org.apache.hadoop.mapreduce.RecordReader<ImmutableBytesWritable,Result>	createRecordReader(org.apache.hadoop.mapreduce.InputSplit split, org.apache.hadoop.mapreduce.TaskAttemptContext context) Builds a TableRecordReader.
protected Admin	getAdmin() Allows subclasses to get the Admin.
protected RegionLocator	getRegionLocator() Allows subclasses to get the RegionLocator.
Scan	getScan() Gets the scan defining the actual details like columns etc.
List<org.apache.hadoop.mapreduce.InputSplit>	getSplits(org.apache.hadoop.mapreduce.JobContext context) Calculates the splits that will serve as input for the map tasks.
protected Pair<byte[][],byte[][]>	getStartEndKeys()
protected Table	getTable() Allows subclasses to get the Table.
protected boolean	includeRegionInSplit(byte[] startKey, byte[] endKey) Test if the given region is to be included in the InputSplit while splitting the regions of a table.
protected void	initialize(org.apache.hadoop.mapreduce.JobContext context) Handle subclass specific set up.
protected void	initializeTable(Connection connection, TableName tableName) Allows subclasses to initialize the table information.
void	setScan(Scan scan) Sets the scan defining the actual details like columns etc.
protected void	setTableRecordReader(TableRecordReader tableRecordReader) Allows subclasses to set the TableRecordReader.

Methods inherited from class java.lang.Object

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

Field Detail

MAPREDUCE_INPUT_AUTOBALANCE

public static final String MAPREDUCE_INPUT_AUTOBALANCE

Specify if we enable auto-balance to set number of mappers in M/R jobs.

See Also:

Constant Field Values

MAX_AVERAGE_REGION_SIZE

public static final String MAX_AVERAGE_REGION_SIZE

In auto-balance, we split input by ave region size, if calculated region size is too big, we can set it.

See Also:

Constant Field Values

NUM_MAPPERS_PER_REGION

public static final String NUM_MAPPERS_PER_REGION

Set the number of Mappers for each region, all regions have same number of Mappers

See Also:

Constant Field Values

Constructor Detail

TableInputFormatBase

public TableInputFormatBase()

Method Detail

createRecordReader

public org.apache.hadoop.mapreduce.RecordReader<ImmutableBytesWritable,Result> createRecordReader(org.apache.hadoop.mapreduce.InputSplit split,
                                                                                                  org.apache.hadoop.mapreduce.TaskAttemptContext context)
                                                                                           throws IOException

Builds a TableRecordReader. If no TableRecordReader was provided, uses the default.

Specified by:

createRecordReader in class org.apache.hadoop.mapreduce.InputFormat<ImmutableBytesWritable,Result>

Parameters:

split - The split to work with.

context - The current context.

Returns:

The newly created record reader.

Throws:

IOException - When creating the reader fails.

See Also:

InputFormat.createRecordReader( org.apache.hadoop.mapreduce.InputSplit, org.apache.hadoop.mapreduce.TaskAttemptContext)

getStartEndKeys

protected Pair<byte[][],byte[][]> getStartEndKeys()
                                           throws IOException

Throws:

IOException

getSplits

public List<org.apache.hadoop.mapreduce.InputSplit> getSplits(org.apache.hadoop.mapreduce.JobContext context)
                                                       throws IOException

Calculates the splits that will serve as input for the map tasks.

Specified by:

getSplits in class org.apache.hadoop.mapreduce.InputFormat<ImmutableBytesWritable,Result>

Parameters:

context - The current job context.

Returns:

The list of input splits.

Throws:

IOException - When creating the list of splits fails.

See Also:

InputFormat.getSplits( org.apache.hadoop.mapreduce.JobContext)

createNInputSplitsUniform

protected List<org.apache.hadoop.mapreduce.InputSplit> createNInputSplitsUniform(org.apache.hadoop.mapreduce.InputSplit split,
                                                                                 int n)
                                                                          throws org.apache.hadoop.hbase.exceptions.IllegalArgumentIOException

Create n splits for one InputSplit, For now only support uniform distribution

Parameters:

split - A TableSplit corresponding to a range of rowkeys

n - Number of ranges after splitting. Pass 1 means no split for the range Pass 2 if you want to split the range in two;

Returns:

A list of TableSplit, the size of the list is n

Throws:

org.apache.hadoop.hbase.exceptions.IllegalArgumentIOException - throws IllegalArgumentIOException

calculateAutoBalancedSplits

public List<org.apache.hadoop.mapreduce.InputSplit> calculateAutoBalancedSplits(List<org.apache.hadoop.mapreduce.InputSplit> splits,
                                                                                long maxAverageRegionSize)
                                                                         throws IOException

Calculates the number of MapReduce input splits for the map tasks. The number of MapReduce input splits depends on the average region size. Make it 'public' for testing

Parameters:

splits - The list of input splits before balance.

maxAverageRegionSize - max Average region size for one mapper

Returns:

The list of input splits.

Throws:

IOException - When creating the list of splits fails.

See Also:

InputFormat.getSplits( org.apache.hadoop.mapreduce.JobContext)

includeRegionInSplit

protected boolean includeRegionInSplit(byte[] startKey,
                                       byte[] endKey)

Test if the given region is to be included in the InputSplit while splitting the regions of a table.

This optimization is effective when there is a specific reasoning to exclude an entire region from the M-R job, (and hence, not contributing to the InputSplit), given the start and end keys of the same.
Useful when we need to remember the last-processed top record and revisit the [last, current) interval for M-R processing, continuously. In addition to reducing InputSplits, reduces the load on the region server as well, due to the ordering of the keys.

Note: It is possible that endKey.length() == 0 , for the last (recent) region.
Override this method, if you want to bulk exclude regions altogether from M-R. By default, no region is excluded( i.e. all regions are included).

Parameters:

startKey - Start key of the region

endKey - End key of the region

Returns:

true, if this region needs to be included as part of the input (default).

getRegionLocator

protected RegionLocator getRegionLocator()

Allows subclasses to get the RegionLocator.

getTable

protected Table getTable()

Allows subclasses to get the Table.

getAdmin

protected Admin getAdmin()

Allows subclasses to get the Admin.

initializeTable

protected void initializeTable(Connection connection,
                               TableName tableName)
                        throws IOException

Allows subclasses to initialize the table information.

Parameters:

connection - The Connection to the HBase cluster. MUST be unmanaged. We will close.

tableName - The TableName of the table to process. n

Throws:

IOException

getScan

public Scan getScan()

Gets the scan defining the actual details like columns etc.

Returns:

The internal scan instance.

setScan

public void setScan(Scan scan)

Sets the scan defining the actual details like columns etc.

Parameters:

scan - The scan to set.

setTableRecordReader

protected void setTableRecordReader(TableRecordReader tableRecordReader)

Allows subclasses to set the TableRecordReader.

Parameters:

tableRecordReader - A different TableRecordReader implementation.

initialize

protected void initialize(org.apache.hadoop.mapreduce.JobContext context)
                   throws IOException

Handle subclass specific set up. Each of the entry points used by the MapReduce framework, createRecordReader(InputSplit, TaskAttemptContext) and getSplits(JobContext), will call initialize(JobContext) as a convenient centralized location to handle retrieving the necessary configuration information and calling initializeTable(Connection, TableName). Subclasses should implement their initialize call such that it is safe to call multiple times. The current TableInputFormatBase implementation relies on a non-null table reference to decide if an initialize call is needed, but this behavior may change in the future. In particular, it is critical that initializeTable not be called multiple times since this will leak Connection instances.

Throws:

IOException

closeTable

protected void closeTable()
                   throws IOException

Close the Table and related objects that were initialized via initializeTable(Connection, TableName). n

Throws:

IOException