@InterfaceAudience.Public @InterfaceStability.Evolving public class TableSnapshotInputFormat extends org.apache.hadoop.mapreduce.InputFormat<ImmutableBytesWritable,Result>
ExportSnapshottool, 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,
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
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.
|Modifier and Type||Class and Description|
|Constructor and Description|
|Modifier and Type||Method and Description|
Configures the job to use TableSnapshotInputFormat to read from a snapshot.
public org.apache.hadoop.mapreduce.RecordReader<ImmutableBytesWritable,Result> createRecordReader(org.apache.hadoop.mapreduce.InputSplit split, org.apache.hadoop.mapreduce.TaskAttemptContext context) throws IOException
public List<org.apache.hadoop.mapreduce.InputSplit> getSplits(org.apache.hadoop.mapreduce.JobContext job) throws IOException, InterruptedException
public static void setInput(org.apache.hadoop.mapreduce.Job job, String snapshotName, org.apache.hadoop.fs.Path restoreDir) throws IOException
job- the job to configure
snapshotName- the name of the snapshot to read from
restoreDir- 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.
IOException- if an error occurs
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