Hadoop Questions and Answers Part-9

1. For ________ the HBase Master UI provides information about the HBase Master uptime.
a) HBase
b) Oozie
c) Kafka
d) All of the mentioned

  Discussion

Answer: a
Explanation: HBase Master UI provides information about the number of live, dead and transitional servers, logs, ZooKeeper information, debug dumps, and thread stacks.

2. During start up, the ___________ loads the file system state from the fsimage and the edits log file.
a) DataNode
b) NameNode
c) ActionNode
d) None of the mentioned

  Discussion

Answer: b
Explanation: HDFS is implemented on any computer which can run Java can host a NameNode/DataNode on it.

3. In order to read any file in HDFS, instance of __________ is required.
a) filesystem
b) datastream
c) outstream
d) inputstream

  Discussion

Answer: a
Explanation: InputDataStream is used to read data from file.

4. Point out the correct statement.
a) The framework groups Reducer inputs by keys
b) The shuffle and sort phases occur simultaneously i.e. while outputs are being fetched they are merged
c) Since JobConf.setOutputKeyComparatorClass(Class) can be used to control how intermediate keys are grouped, these can be used in conjunction to simulate secondary sort on values
d) All of the mentioned

  Discussion

Answer: d
Explanation: If equivalence rules for keys while grouping the intermediates are different from those for grouping keys before reduction, then one may specify a Comparator.

5. ______________ is method to copy byte from input stream to any other stream in Hadoop.
a) IOUtils
b) Utils
c) IUtils
d) All of the mentioned

  Discussion

Answer: a
Explanation: IOUtils class is static method in Java interface.

6. _____________ is used to read data from bytes buffers.
a) write()
b) read()
c) readwrite()
d) all of the mentioned

  Discussion

Answer: a
Explanation: readfully method can also be used instead of read method.

7. Point out the wrong statement.
a) The framework calls reduce method for each <key, (list of values)> pair in the grouped inputs
b) The output of the Reducer is re-sorted
c) reduce method reduces values for a given key
d) None of the mentioned

  Discussion

Answer: b
Explanation: The output of the Reducer is not re-sorted.

8. Interface ____________ reduces a set of intermediate values which share a key to a smaller set of values.
a) Mapper
b) Reducer
c) Writable
d) Readable

  Discussion

Answer: b
Explanation: Reducer implementations can access the JobConf for the job.

9. Reducer is input the grouped output of a ____________
a) Mapper
b) Reducer
c) Writable
d) Readable

  Discussion

Answer: a
Explanation: In the phase the framework, for each Reducer, fetches the relevant partition of the output of all the Mappers, via HTTP.

10. The output of the reduce task is typically written to the FileSystem via ____________
a) OutputCollector
b) InputCollector
c) OutputCollect
d) All of the mentioned

  Discussion

Answer: a
Explanation: In reduce phase the reduce(Object, Iterator, OutputCollector, Reporter) method is called for each pair in the grouped inputs.