RestoreSnapshotHelper (Apache HBase 1.4.11 API)

java.lang.Object
- org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper

```
@InterfaceAudience.Private
public class RestoreSnapshotHelper
extends Object
```
Helper to Restore/Clone a Snapshot
The helper assumes that a table is already created, and by calling restore() the content present in the snapshot will be restored as the new content of the table.
Clone from Snapshot: If the target table is empty, the restore operation is just a "clone operation", where the only operations are:
- for each region in the snapshot create a new region (note that the region will have a different name, since the encoding contains the table name)
- for each file in the region create a new HFileLink to point to the original file.
- restore the logs, if any
Restore from Snapshot:
- for each region in the table verify which are available in the snapshot and which are not
  - if the region is not present in the snapshot, remove it.
  - if the region is present in the snapshot
    - for each file in the table region verify which are available in the snapshot
      
      if the hfile is not present in the snapshot, remove it
      if the hfile is present, keep it (nothing to do)
    - for each file in the snapshot region but not in the table
      
      create a new HFileLink that point to the original file
- for each region in the snapshot not present in the current table state
  - create a new region and for each file in the region create a new HFileLink (This is the same as the clone operation)
- restore the logs, if any

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class RestoreSnapshotHelper.RestoreMetaChanges
Describe the set of operations needed to update hbase:meta after restore.

Nested Classes
Modifier and Type	Class and Description
`static class`	`RestoreSnapshotHelper.RestoreMetaChanges` Describe the set of operations needed to update hbase:meta after restore.

Constructor Summary

Constructors
Constructor and Description
`RestoreSnapshotHelper(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, SnapshotManifest manifest, HTableDescriptor tableDescriptor, org.apache.hadoop.fs.Path rootDir, ForeignExceptionDispatcher monitor, MonitoredTask status)`
`RestoreSnapshotHelper(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, SnapshotManifest manifest, HTableDescriptor tableDescriptor, org.apache.hadoop.fs.Path rootDir, ForeignExceptionDispatcher monitor, MonitoredTask status, boolean createBackRefs)`

Method Summary

Methods
Modifier and Type	Method and Description
`HRegionInfo`	`cloneRegionInfo(HRegionInfo snapshotRegionInfo)` Create a new `HRegionInfo` from the snapshot region info.
`static HRegionInfo`	`cloneRegionInfo(TableName tableName, HRegionInfo snapshotRegionInfo)`
`static RestoreSnapshotHelper.RestoreMetaChanges`	`copySnapshotForScanner(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path rootDir, org.apache.hadoop.fs.Path restoreDir, String snapshotName)` Copy the snapshot files for a snapshot scanner, discards meta changes.
`RestoreSnapshotHelper.RestoreMetaChanges`	`restoreHdfsRegions()` Restore the on-disk table to a specified snapshot state.
`static void`	`restoreSnapshotACL(org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription snapshot, TableName newTableName, org.apache.hadoop.conf.Configuration conf)`

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

Constructor Detail

RestoreSnapshotHelper

public RestoreSnapshotHelper(org.apache.hadoop.conf.Configuration conf,
                     org.apache.hadoop.fs.FileSystem fs,
                     SnapshotManifest manifest,
                     HTableDescriptor tableDescriptor,
                     org.apache.hadoop.fs.Path rootDir,
                     ForeignExceptionDispatcher monitor,
                     MonitoredTask status)

RestoreSnapshotHelper

public RestoreSnapshotHelper(org.apache.hadoop.conf.Configuration conf,
                     org.apache.hadoop.fs.FileSystem fs,
                     SnapshotManifest manifest,
                     HTableDescriptor tableDescriptor,
                     org.apache.hadoop.fs.Path rootDir,
                     ForeignExceptionDispatcher monitor,
                     MonitoredTask status,
                     boolean createBackRefs)

Method Detail

restoreHdfsRegions

public RestoreSnapshotHelper.RestoreMetaChanges restoreHdfsRegions()
                                                            throws IOException

Restore the on-disk table to a specified snapshot state.

Returns:: the set of regions touched by the restore operation
Throws:: IOException

cloneRegionInfo
```
public HRegionInfo cloneRegionInfo(HRegionInfo snapshotRegionInfo)
```
Create a new HRegionInfo from the snapshot region info. Keep the same startKey, endKey, regionId and split information but change the table name.

Parameters:
snapshotRegionInfo - Info for region to clone.

Returns:
the new HRegion instance

cloneRegionInfo

public static HRegionInfo cloneRegionInfo(TableName tableName,
                          HRegionInfo snapshotRegionInfo)

copySnapshotForScanner

public static RestoreSnapshotHelper.RestoreMetaChanges copySnapshotForScanner(org.apache.hadoop.conf.Configuration conf,
                                                              org.apache.hadoop.fs.FileSystem fs,
                                                              org.apache.hadoop.fs.Path rootDir,
                                                              org.apache.hadoop.fs.Path restoreDir,
                                                              String snapshotName)
                                                                       throws IOException

Copy the snapshot files for a snapshot scanner, discards meta changes.

Parameters:: conf -; fs -; rootDir -; restoreDir -; snapshotName -
Throws:: IOException

restoreSnapshotACL

public static void restoreSnapshotACL(org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription snapshot,
                      TableName newTableName,
                      org.apache.hadoop.conf.Configuration conf)
                               throws IOException

Throws:: IOException

Class RestoreSnapshotHelper

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

RestoreSnapshotHelper

RestoreSnapshotHelper

Method Detail

restoreHdfsRegions

cloneRegionInfo

cloneRegionInfo

copySnapshotForScanner

restoreSnapshotACL