NameNodeLayoutVersion.Feature (Apache Hadoop HDFS 2.8.2 API)

java.lang.Object
- java.lang.Enum<NameNodeLayoutVersion.Feature>
- - org.apache.hadoop.hdfs.server.namenode.NameNodeLayoutVersion.Feature

All Implemented Interfaces:

Serializable, Comparable<NameNodeLayoutVersion.Feature>, LayoutVersion.LayoutFeature

Enclosing class:

org.apache.hadoop.hdfs.server.namenode.NameNodeLayoutVersion
```
public static enum NameNodeLayoutVersion.Feature
extends Enum<NameNodeLayoutVersion.Feature>
implements LayoutVersion.LayoutFeature
```
Enums for features that change the layout version.

To add a new layout version:
- Define a new enum constant with a short enum name, the new layout version and description of the added feature.
- When adding a layout version with an ancestor that is not same as its immediate predecessor, use the constructor where a specific ancestor can be passed.
- Specify a minimum compatible layout version. The minimum compatible layout version is the earliest prior version to which a downgrade is possible after initiating rolling upgrade. If the feature cannot satisfy compatibility with any prior version, then set its minimum compatible lqyout version to itself to indicate that downgrade is impossible. Satisfying compatibility might require adding logic to the new feature to reject operations or handle them differently while rolling upgrade is in progress. In general, it's possible to satisfy compatiblity for downgrade if the new feature just involves adding new edit log ops. Deeper structural changes, such as changing the way we place files in the metadata directories, might be incompatible. Feature implementations should strive for compatibility, because it's in the best interest of our users to support downgrade.

Enum Constant Summary

Enum Constants
Enum Constant and Description
`APPEND_NEW_BLOCK`
`BLOCK_STORAGE_POLICY`
`CREATE_OVERWRITE`
`EDITLOG_LENGTH`
`QUOTA_BY_STORAGE_TYPE`
`ROLLING_UPGRADE`
`TRUNCATE`
`XATTRS`
`XATTRS_NAMESPACE_EXT`

Method Summary

Methods
Modifier and Type	Method and Description
`LayoutVersion.FeatureInfo`	`getInfo()`
`static NameNodeLayoutVersion.Feature`	`valueOf(String name)` Returns the enum constant of this type with the specified name.
`static NameNodeLayoutVersion.Feature[]`	`values()` Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum
clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait

- Enum Constant Detail
  - ROLLING_UPGRADE
```
public static final NameNodeLayoutVersion.Feature ROLLING_UPGRADE
```
  - EDITLOG_LENGTH
```
public static final NameNodeLayoutVersion.Feature EDITLOG_LENGTH
```
  - XATTRS
```
public static final NameNodeLayoutVersion.Feature XATTRS
```
  - CREATE_OVERWRITE
```
public static final NameNodeLayoutVersion.Feature CREATE_OVERWRITE
```
  - XATTRS_NAMESPACE_EXT
```
public static final NameNodeLayoutVersion.Feature XATTRS_NAMESPACE_EXT
```
  - BLOCK_STORAGE_POLICY
```
public static final NameNodeLayoutVersion.Feature BLOCK_STORAGE_POLICY
```
  - TRUNCATE
```
public static final NameNodeLayoutVersion.Feature TRUNCATE
```
  - APPEND_NEW_BLOCK
```
public static final NameNodeLayoutVersion.Feature APPEND_NEW_BLOCK
```
  - QUOTA_BY_STORAGE_TYPE
```
public static final NameNodeLayoutVersion.Feature QUOTA_BY_STORAGE_TYPE
```
- Method Detail
  - values
```
public static NameNodeLayoutVersion.Feature[] values()
```
    Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:
```
for (NameNodeLayoutVersion.Feature c : NameNodeLayoutVersion.Feature.values())
    System.out.println(c);
```
    Returns:
    an array containing the constants of this enum type, in the order they are declared
  - valueOf
```
public static NameNodeLayoutVersion.Feature valueOf(String name)
```
    Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
    
    Parameters:
    name - the name of the enum constant to be returned.
    
    Returns:
    the enum constant with the specified name
    
    Throws:
    
    IllegalArgumentException - if this enum type has no constant with the specified name
    
    NullPointerException - if the argument is null
  - getInfo
```
public LayoutVersion.FeatureInfo getInfo()
```
    Specified by:
    
    getInfo in interface LayoutVersion.LayoutFeature

Enum NameNodeLayoutVersion.Feature

Enum Constant Summary

Method Summary

Methods inherited from class java.lang.Enum

Methods inherited from class java.lang.Object

Enum Constant Detail

ROLLING_UPGRADE

EDITLOG_LENGTH

XATTRS

CREATE_OVERWRITE

XATTRS_NAMESPACE_EXT

BLOCK_STORAGE_POLICY

TRUNCATE

APPEND_NEW_BLOCK

QUOTA_BY_STORAGE_TYPE

Method Detail

values

valueOf

getInfo