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java.lang.Objectorg.apache.hadoop.hbase.client.AbstractClientScanner
org.apache.hadoop.hbase.client.TableSnapshotScanner
@InterfaceAudience.Public @InterfaceStability.Evolving public class TableSnapshotScanner
A Scanner which performs a scan over snapshot files. Using this class requires copying the snapshot to a temporary empty directory, which will copy the snapshot reference files into that directory. Actual data files are not copied.
This also allows one to run the scan from an
online or offline hbase cluster. The snapshot files can be exported by using the
ExportSnapshot
tool, to a pure-hdfs cluster, and this scanner can be used to
run the scan directly over the snapshot files. The snapshot should not be deleted while there
are open scanners reading from snapshot files.
An internal RegionScanner is used to execute the Scan
obtained
from the user for each region in the snapshot.
HBase owns all the data and snapshot files on the filesystem. Only the HBase user can read from snapshot files and data files. HBase also enforces security because all the requests are handled by the server layer, and the user cannot read from the data files directly. To read from snapshot files directly from the file system, the user who is running the MR job must have sufficient permissions to access snapshot and reference files. This means that to run mapreduce over snapshot files, the job has to be run as the HBase user or the user must have group or other priviledges in the filesystem (See HBASE-8369). Note that, given other users access to read from snapshot/data files will completely circumvent the access control enforced by HBase.
TableSnapshotInputFormat
Field Summary |
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Fields inherited from class org.apache.hadoop.hbase.client.AbstractClientScanner |
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scanMetrics |
Constructor Summary | |
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TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf,
org.apache.hadoop.fs.Path rootDir,
org.apache.hadoop.fs.Path restoreDir,
String snapshotName,
Scan scan)
Creates a TableSnapshotScanner. |
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TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf,
org.apache.hadoop.fs.Path restoreDir,
String snapshotName,
Scan scan)
Creates a TableSnapshotScanner. |
Method Summary | |
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void |
close()
Closes the scanner and releases any resources it has allocated |
Result |
next()
Grab the next row's worth of values. |
boolean |
renewLease()
Allow the client to renew the scanner's lease on the server. |
Methods inherited from class org.apache.hadoop.hbase.client.AbstractClientScanner |
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getScanMetrics, initScanMetrics, iterator, next |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.Path restoreDir, String snapshotName, Scan scan) throws IOException
conf
- the configurationrestoreDir
- a temporary directory to copy the snapshot files into. Current user should
have write permissions to this directory, and this should not be a subdirectory of rootdir.
The scanner deletes the contents of the directory once the scanner is closed.snapshotName
- the name of the snapshot to read fromscan
- a Scan representing scan parameters
IOException
- in case of errorpublic TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.Path rootDir, org.apache.hadoop.fs.Path restoreDir, String snapshotName, Scan scan) throws IOException
conf
- the configurationrootDir
- root directory for HBase.restoreDir
- a temporary directory to copy the snapshot files into. Current user should
have write permissions to this directory, and this should not be a subdirectory of rootdir.
The scanner deletes the contents of the directory once the scanner is closed.snapshotName
- the name of the snapshot to read fromscan
- a Scan representing scan parameters
IOException
- in case of errorMethod Detail |
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public Result next() throws IOException
ResultScanner
IOException
- epublic void close()
ResultScanner
public boolean renewLease()
AbstractClientScanner
renewLease
in class AbstractClientScanner
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