@InterfaceAudience.Public @InterfaceStability.Evolving public class TableSnapshotInputFormat extends <any>
ExportSnapshot
tool, to a pure-hdfs cluster,
and this InputFormat can be used to run the mapreduce job directly over the snapshot files.
The snapshot should not be deleted while there are jobs reading from snapshot files.
Usage is similar to TableInputFormat, and
TableMapReduceUtil.initTableSnapshotMapperJob(String, Scan, Class, Class, Class, Job,
boolean, Path)
can be used to configure the job.
Job job = new Job(conf);
Scan scan = new Scan();
TableMapReduceUtil.initTableSnapshotMapperJob(snapshotName,
scan, MyTableMapper.class, MyMapKeyOutput.class,
MyMapOutputValueWritable.class, job, true);
Internally, this input format restores the snapshot into the given tmp directory. Similar to
TableInputFormat
an InputSplit is created per region. The region is opened for reading
from each RecordReader. An internal RegionScanner is used to execute the
CellScanner
obtained from the user.
HBase owns all the data and snapshot files on the filesystem. Only the 'hbase' user can read from snapshot files and data files. 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 MR job has to be run as the HBase user or the user must have group or other privileges 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.
TableSnapshotScanner
Modifier and Type | Class and Description |
---|---|
static class |
TableSnapshotInputFormat.TableSnapshotRegionSplit |
Constructor and Description |
---|
TableSnapshotInputFormat() |
Modifier and Type | Method and Description |
---|---|
<any> |
createRecordReader(InputSplit split,
TaskAttemptContext context) |
java.util.List<InputSplit> |
getSplits(JobContext job) |
static void |
setInput(Job job,
java.lang.String snapshotName,
Path restoreDir)
Configures the job to use TableSnapshotInputFormat to read from a snapshot.
|
public <any> createRecordReader(InputSplit split, TaskAttemptContext context) throws java.io.IOException
java.io.IOException
public java.util.List<InputSplit> getSplits(JobContext job) throws java.io.IOException, java.lang.InterruptedException
java.io.IOException
java.lang.InterruptedException
public static void setInput(Job job, java.lang.String snapshotName, Path restoreDir) throws java.io.IOException
job
- the job to configuresnapshotName
- the name of the snapshot to read fromrestoreDir
- a temporary directory to restore the snapshot into. Current user should
have write permissions to this directory, and this should not be a subdirectory of rootdir.
After the job is finished, restoreDir can be deleted.java.io.IOException
- if an error occurs