org.apache.hadoop.hbase.regionserver

Class InputStreamBlockDistribution

java.lang.Object

org.apache.hadoop.hbase.regionserver.InputStreamBlockDistribution

@InterfaceAudience.Private
public class InputStreamBlockDistribution
extends Object

Computes the HDFSBlockDistribution for a file based on the underlying located blocks for an HdfsDataInputStream reading that file. The backing DFSInputStream.getAllBlocks involves allocating an array of numBlocks size per call. It may also involve calling the namenode, if the DFSInputStream has not fetched all the blocks yet. In order to avoid allocation pressure, we cache the computed distribution for a configurable period of time.

This class only gets instantiated for the first FSDataInputStream of each StoreFile (i.e. the one backing HStoreFile.initialReader). It's then used to dynamically update the value returned by HStoreFile.getHDFSBlockDistribution().

Once the backing FSDataInputStream is closed, we should not expect the distribution result to change anymore. This is ok becuase the initialReader's InputStream is only closed when the StoreFile itself is closed, at which point nothing will be querying getHDFSBlockDistribution anymore. If/When the StoreFile is reopened, a new InputStreamBlockDistribution will be created for the new initialReader.

Constructor Summary

Constructors

Constructor and Description
InputStreamBlockDistribution(org.apache.hadoop.fs.FSDataInputStream stream, StoreFileInfo fileInfo) This should only be called for the first FSDataInputStream of a StoreFile, in HStoreFile.open().

Method Summary

Modifier and Type	Method and Description
HDFSBlocksDistribution	getHDFSBlockDistribution() Get the HDFSBlocksDistribution derived from the StoreFile input stream, re-computing if cache is expired.
static boolean	isEnabled(org.apache.hadoop.conf.Configuration conf) True if we should derive StoreFile HDFSBlockDistribution from the underlying input stream

Methods inherited from class java.lang.Object

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

Constructor Detail

InputStreamBlockDistribution

public InputStreamBlockDistribution(org.apache.hadoop.fs.FSDataInputStream stream,
                                    StoreFileInfo fileInfo)

This should only be called for the first FSDataInputStream of a StoreFile, in HStoreFile.open().

Parameters:

stream - the input stream to derive locality from

fileInfo - the StoreFileInfo for the related store file

See Also:

InputStreamBlockDistribution

Method Detail

isEnabled

public static boolean isEnabled(org.apache.hadoop.conf.Configuration conf)

True if we should derive StoreFile HDFSBlockDistribution from the underlying input stream

getHDFSBlockDistribution

public HDFSBlocksDistribution getHDFSBlockDistribution()

Get the HDFSBlocksDistribution derived from the StoreFile input stream, re-computing if cache is expired.