Package org.apache.hadoop.hdfs.protocol

Class LayoutVersion

java.lang.Object

org.apache.hadoop.hdfs.protocol.LayoutVersion

@Private
public class LayoutVersion
extends Object

This class tracks changes in the layout version of HDFS. Layout version is changed for following reasons:

1. The layout of how namenode or datanode stores information on disk changes.
2. A new operation code is added to the editlog.
3. Modification such as format of a record, content of a record in editlog or fsimage.

How to update layout version:
When a change requires new layout version, please add an entry into LayoutVersion.Feature with a short enum name, new layout version and description of the change. Please see LayoutVersion.Feature for further details.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	LayoutVersion.Feature	Enums for features that change the layout version before rolling upgrade is supported.
static class	LayoutVersion.FeatureInfo	Feature information.
static interface	LayoutVersion.LayoutFeature	The interface to be implemented by NameNode and DataNode layout features

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BUGFIX_HDFS_2991_VERSION	Version in which HDFS-2991 was fixed.

Constructor Summary

Constructors

Constructor	Description
LayoutVersion()

Method Summary

Modifier and Type	Method	Description
static int	getCurrentLayoutVersion(LayoutVersion.LayoutFeature[] features)	Get the current layout version
static int	getMinimumCompatibleLayoutVersion(LayoutVersion.LayoutFeature[] features)	Gets the minimum compatible layout version.
String	getString(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map, LayoutVersion.LayoutFeature[] values)	Gets formatted string that describes LayoutVersion information.
static boolean	supports(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map, LayoutVersion.LayoutFeature f, int lv)	Returns true if a given feature is supported in the given layout version
static void	updateMap(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map, LayoutVersion.LayoutFeature[] features)

Methods inherited from class java.lang.Object

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

Field Details

BUGFIX_HDFS_2991_VERSION

public static final int BUGFIX_HDFS_2991_VERSION

Version in which HDFS-2991 was fixed. This bug caused OP_ADD to sometimes be skipped for append() calls. If we see such a case when loading the edits, but the version is known to have that bug, we workaround the issue. Otherwise we should consider it a corruption and bail.

See Also:

• Constant Field Values

Constructor Details

LayoutVersion

public LayoutVersion()

Method Details

updateMap

public static void updateMap(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map,
 LayoutVersion.LayoutFeature[] features)

getString

public String getString(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map,
 LayoutVersion.LayoutFeature[] values)

Gets formatted string that describes LayoutVersion information.

supports

public static boolean supports(Map<Integer,SortedSet<LayoutVersion.LayoutFeature>> map,
 LayoutVersion.LayoutFeature f,
 int lv)

Returns true if a given feature is supported in the given layout version

Parameters:

map - layout feature map

f - Feature

lv - LayoutVersion

Returns:

true if f is supported in layout version lv

getCurrentLayoutVersion

public static int getCurrentLayoutVersion(LayoutVersion.LayoutFeature[] features)

Get the current layout version

getMinimumCompatibleLayoutVersion

public static int getMinimumCompatibleLayoutVersion(LayoutVersion.LayoutFeature[] features)

Gets the minimum compatible layout version.

Parameters:

features - all features to check

Returns:

minimum compatible layout version