WALFactory (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.wal.WALFactory

```
@InterfaceAudience.Private
public class WALFactory
extends Object
```
Entry point for users of the Write Ahead Log. Acts as the shim between internal use and the particular WALProvider we use to handle wal requests. Configure which provider gets used with the configuration setting "hbase.wal.provider". Available implementations:
- defaultProvider : whatever provider is standard for the hbase version. Currently "filesystem"
- filesystem : a provider that will run on top of an implementation of the Hadoop FileSystem interface, normally HDFS.
- multiwal : a provider that will use multiple "filesystem" wal instances per region server.
Alternatively, you may provide a custome implementation of WALProvider by class name.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

(package private) static class WALFactory.Providers
Maps between configuration names for providers and implementation classes.

Nested Classes
Modifier and Type	Class and Description
`(package private) static class`	`WALFactory.Providers` Maps between configuration names for providers and implementation classes.

Field Summary

Fields
Modifier and Type	Field and Description
`private org.apache.hadoop.conf.Configuration`	`conf`
`(package private) static String`	`DEFAULT_META_WAL_PROVIDER`
`(package private) static String`	`DEFAULT_WAL_PROVIDER`
`(package private) String`	`factoryId`
`private static org.apache.commons.logging.Log`	`LOG`
`private Class<? extends DefaultWALProvider.Reader>`	`logReaderClass` Configuration-specified WAL Reader used when a custom reader is requested
`(package private) static String`	`META_WAL_PROVIDER`
`(package private) AtomicReference<WALProvider>`	`metaProvider`
`(package private) WALProvider`	`provider`
`private static AtomicReference<WALFactory>`	`singleton`
`private static String`	`SINGLETON_ID`
`private int`	`timeoutMillis` How long to attempt opening in-recovery wals
`static String`	`WAL_PROVIDER`

Constructor Summary

Constructors
Modifier	Constructor and Description
`private`	`WALFactory(org.apache.hadoop.conf.Configuration conf)`
	`WALFactory(org.apache.hadoop.conf.Configuration conf, List<WALActionsListener> listeners, String factoryId)`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`close()` Shutdown all WALs and clean up any underlying storage.
`WAL.Reader`	`createReader(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path)`
`WAL.Reader`	`createReader(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, CancelableProgressable reporter)` Create a reader for the WAL.
`WAL.Reader`	`createReader(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, CancelableProgressable reporter, boolean allowCustom)`
`static WAL.Reader`	`createReader(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, org.apache.hadoop.conf.Configuration configuration)` Create a reader for the given path, accept custom reader classes from conf.
`(package private) static WAL.Reader`	`createReader(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, org.apache.hadoop.conf.Configuration configuration, CancelableProgressable reporter)` Create a reader for the given path, accept custom reader classes from conf.
`static WAL.Reader`	`createReaderIgnoreCustomClass(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, org.apache.hadoop.conf.Configuration configuration)` Create a reader for the given path, ignore custom reader classes from conf.
`WALProvider.Writer`	`createRecoveredEditsWriter(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path)` should be package-private, visible for recovery testing.
`(package private) static WALProvider.Writer`	`createRecoveredEditsWriter(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, org.apache.hadoop.conf.Configuration configuration)` If you already have a WALFactory, you should favor the instance method.
`WALProvider.Writer`	`createWALWriter(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path)` Create a writer for the WAL.
`static WALProvider.Writer`	`createWALWriter(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, org.apache.hadoop.conf.Configuration configuration)` If you already have a WALFactory, you should favor the instance method.
`static WALFactory`	`getInstance(org.apache.hadoop.conf.Configuration configuration)`
`WAL`	`getMetaWAL(byte[] identifier)`
`(package private) WALProvider`	`getProvider(String key, String defaultValue, List<WALActionsListener> listeners, String providerId)` instantiate a provider from a config property.
`WAL`	`getWAL(byte[] identifier)`
`void`	`shutdown()` Tell the underlying WAL providers to shut down, but do not clean up underlying storage.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOG

private static final org.apache.commons.logging.Log LOG

WAL_PROVIDER

public static final String WAL_PROVIDER

See Also:: Constant Field Values

DEFAULT_WAL_PROVIDER

static final String DEFAULT_WAL_PROVIDER

META_WAL_PROVIDER
```
static final String META_WAL_PROVIDER
```
See Also:
Constant Field Values

DEFAULT_META_WAL_PROVIDER

static final String DEFAULT_META_WAL_PROVIDER

factoryId
```
final String factoryId
```

provider
```
final WALProvider provider
```

metaProvider

final AtomicReference<WALProvider> metaProvider

logReaderClass
```
private final Class<? extends DefaultWALProvider.Reader> logReaderClass
```
Configuration-specified WAL Reader used when a custom reader is requested

timeoutMillis
```
private final int timeoutMillis
```
How long to attempt opening in-recovery wals

conf

private final org.apache.hadoop.conf.Configuration conf

singleton

private static final AtomicReference<WALFactory> singleton

SINGLETON_ID

private static final String SINGLETON_ID

Constructor Detail
- WALFactory
```
private WALFactory(org.apache.hadoop.conf.Configuration conf)
```
- WALFactory
```
public WALFactory(org.apache.hadoop.conf.Configuration conf,
          List<WALActionsListener> listeners,
          String factoryId)
           throws IOException
```
  Parameters:
  conf - must not be null, will keep a reference to read params in later reader/writer instances.
  listeners - may be null. will be given to all created wals (and not meta-wals)
  factoryId - a unique identifier for this factory. used i.e. by filesystem implementations to make a directory
  
  Throws:
  
  IOException

Method Detail

getProvider

WALProvider getProvider(String key,
                      String defaultValue,
                      List<WALActionsListener> listeners,
                      String providerId)
                  throws IOException

instantiate a provider from a config property. requires conf to have already been set (as well as anything the provider might need to read).

Throws:: IOException

close
```
public void close()
           throws IOException
```
Shutdown all WALs and clean up any underlying storage. Use only when you will not need to replay and edits that have gone to any wals from this factory.

Throws:

IOException

shutdown
```
public void shutdown()
              throws IOException
```
Tell the underlying WAL providers to shut down, but do not clean up underlying storage. If you are not ending cleanly and will need to replay edits from this factory's wals, use this method if you can as it will try to leave things as tidy as possible.

Throws:

IOException

getWAL
```
public WAL getWAL(byte[] identifier)
           throws IOException
```
Parameters:
identifier - may not be null, contents will not be altered

Throws:

IOException

getMetaWAL
```
public WAL getMetaWAL(byte[] identifier)
               throws IOException
```
Parameters:
identifier - may not be null, contents will not be altered

Throws:

IOException

createReader

public WAL.Reader createReader(org.apache.hadoop.fs.FileSystem fs,
                      org.apache.hadoop.fs.Path path)
                        throws IOException

Throws:: IOException

createReader
```
public WAL.Reader createReader(org.apache.hadoop.fs.FileSystem fs,
                      org.apache.hadoop.fs.Path path,
                      CancelableProgressable reporter)
                        throws IOException
```
Create a reader for the WAL. If you are reading from a file that's being written to and need to reopen it multiple times, use WAL.Reader.reset() instead of this method then just seek back to the last known good position.

Returns:
A WAL reader. Close when done with it.

Throws:

IOException

createReader

public WAL.Reader createReader(org.apache.hadoop.fs.FileSystem fs,
                      org.apache.hadoop.fs.Path path,
                      CancelableProgressable reporter,
                      boolean allowCustom)
                        throws IOException

Throws:: IOException

createWALWriter

public WALProvider.Writer createWALWriter(org.apache.hadoop.fs.FileSystem fs,
                                 org.apache.hadoop.fs.Path path)
                                   throws IOException

Create a writer for the WAL. should be package-private. public only for tests and Compressor

Returns:: A WAL writer. Close when done with it.
Throws:: IOException

createRecoveredEditsWriter

public WALProvider.Writer createRecoveredEditsWriter(org.apache.hadoop.fs.FileSystem fs,
                                            org.apache.hadoop.fs.Path path)
                                              throws IOException

should be package-private, visible for recovery testing.

Returns:: an overwritable writer for recovered edits. caller should close.
Throws:: IOException

getInstance

public static WALFactory getInstance(org.apache.hadoop.conf.Configuration configuration)

createReader

public static WAL.Reader createReader(org.apache.hadoop.fs.FileSystem fs,
                      org.apache.hadoop.fs.Path path,
                      org.apache.hadoop.conf.Configuration configuration)
                               throws IOException

Create a reader for the given path, accept custom reader classes from conf. If you already have a WALFactory, you should favor the instance method.

Returns:: a WAL Reader, caller must close.
Throws:: IOException

createReader

static WAL.Reader createReader(org.apache.hadoop.fs.FileSystem fs,
                      org.apache.hadoop.fs.Path path,
                      org.apache.hadoop.conf.Configuration configuration,
                      CancelableProgressable reporter)
                        throws IOException

Create a reader for the given path, accept custom reader classes from conf. If you already have a WALFactory, you should favor the instance method.

Returns:: a WAL Reader, caller must close.
Throws:: IOException

createReaderIgnoreCustomClass

public static WAL.Reader createReaderIgnoreCustomClass(org.apache.hadoop.fs.FileSystem fs,
                                       org.apache.hadoop.fs.Path path,
                                       org.apache.hadoop.conf.Configuration configuration)
                                                throws IOException

Create a reader for the given path, ignore custom reader classes from conf. If you already have a WALFactory, you should favor the instance method. only public pending move of Compressor

Returns:: a WAL Reader, caller must close.
Throws:: IOException

createRecoveredEditsWriter

static WALProvider.Writer createRecoveredEditsWriter(org.apache.hadoop.fs.FileSystem fs,
                                            org.apache.hadoop.fs.Path path,
                                            org.apache.hadoop.conf.Configuration configuration)
                                              throws IOException

If you already have a WALFactory, you should favor the instance method.

Returns:: a Writer that will overwrite files. Caller must close.
Throws:: IOException

createWALWriter

public static WALProvider.Writer createWALWriter(org.apache.hadoop.fs.FileSystem fs,
                                 org.apache.hadoop.fs.Path path,
                                 org.apache.hadoop.conf.Configuration configuration)
                                          throws IOException

If you already have a WALFactory, you should favor the instance method.

Returns:: a writer that won't overwrite files. Caller must close.
Throws:: IOException

Class WALFactory

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

WAL_PROVIDER

DEFAULT_WAL_PROVIDER

META_WAL_PROVIDER

DEFAULT_META_WAL_PROVIDER

factoryId

provider

metaProvider

logReaderClass

timeoutMillis

conf

singleton

SINGLETON_ID

Constructor Detail

WALFactory

WALFactory

Method Detail

getProvider

close

shutdown

getWAL

getMetaWAL

createReader

createReader

createReader

createWALWriter

createRecoveredEditsWriter

getInstance

createReader

createReader

createReaderIgnoreCustomClass

createRecoveredEditsWriter

createWALWriter