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);
     }
   }
 

Field Summary

Fields

Modifier and Type	Field and Description
static String	INPUT_AUTOBALANCE_MAXSKEWRATIO Specify if ratio for data skew in M/R jobs, it goes well with the enabling hbase.mapreduce .input.autobalance property.
static String	MAPREDUCE_INPUT_AUTOBALANCE Specify if we enable auto-balance for input in M/R jobs.
static String	TABLE_ROW_TEXTKEY Specify if the row key in table is text (ASCII between 32~126), default is true.

Constructor Summary

Constructors

Constructor and Description
TableInputFormatBase()

Method Summary

Modifier and Type	Method and Description
protected void	closeTable() Close the Table and related objects that were initialized via initializeTable(Connection, TableName).
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.
static byte[]	getSplitKey(byte[] start, byte[] end, boolean isText) select a split point in the region.
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 for input in M/R jobs.

See Also:

Constant Field Values

INPUT_AUTOBALANCE_MAXSKEWRATIO

public static final String INPUT_AUTOBALANCE_MAXSKEWRATIO

Specify if ratio for data skew in M/R jobs, it goes well with the enabling hbase.mapreduce .input.autobalance property.

See Also:

Constant Field Values

TABLE_ROW_TEXTKEY

public static final String TABLE_ROW_TEXTKEY

Specify if the row key in table is text (ASCII between 32~126), default is true. False means the table is using binary row key

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. The number of splits matches the number of regions in a table.

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)

getSplitKey

@InterfaceAudience.Private
public static byte[] getSplitKey(byte[] start,
                                                            byte[] end,
                                                            boolean isText)

select a split point in the region. The selection of the split point is based on an uniform distribution assumption for the keys in a region. Here are some examples:

start key	end key	is text	split point
'a', 'a', 'a', 'b', 'c', 'd', 'e', 'f', 'g'	'a', 'a', 'a', 'f', 'f', 'f'	true	'a', 'a', 'a', 'd', 'd', -78, 50, -77, 51
'1', '1', '1', '0', '0', '0'	'1', '1', '2', '5', '7', '9', '0'	true	'1', '1', '1', -78, -77, -76, -104
'1', '1', '1', '0'	'1', '1', '2', '0'	true	'1', '1', '1', -80
13, -19, 126, 127	13, -19, 127, 0	false	13, -19, 126, -65

Set this function as "public static", make it easier for test.

Parameters:

start - Start key of the region

end - End key of the region

isText - It determines to use text key mode or binary key mode

Returns:

The split point in the region.

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.

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).

Throws:

IOException