Dinesh on Java

1.When is the earliest point at which the reduce method of a given Reducer can be called?
A. As soon as at least one mapper has finished processing its input split.
B. As soon as a mapper has emitted at least one record.
C. Not until all mappers have finished processing all records.
D. It depends on the InputFormat used for the job.

Answer: C

2.Which describes how a client reads a file from HDFS?
A. The client queries the NameNode for the block location(s). The NameNode returns the block
location(s) to the client. The client reads the data directory off the DataNode(s).
B. The client queries all DataNodes in parallel. The DataNode that contains the requested data
responds directly to the client. The client reads the data directly off the DataNode.
C. The client contacts the NameNode for the block location(s). The NameNode then queries the
DataNodes for block locations. The DataNodes respond to the NameNode, and the NameNode
redirects the client to the DataNode that holds the requested data block(s). The client then reads
the data directly off the DataNode.
D. The client contacts the NameNode for the block location(s). The NameNode contacts the
DataNode that holds the requested data block. Data is transferred from the DataNode to the
NameNode, and then from the NameNode to the client.

Answer: A

3.You are developing a combiner that takes as input Text keys, IntWritable values, and emits Text
keys, IntWritable values. Which interface should your class implement?
A. Combiner
B. Mapper
C. Reducer
D. Reducer
E. Combiner
 
Answer: D

4.Indentify the utility that allows you to create and run MapReduce jobs with any executable or script as the mapper and/or the reducer?
A. Oozie
B. Sqoop
C. Flume
D. Hadoop Streaming
E. mapred
 
Answer: D

5.How are keys and values presented and passed to the reducers during a standard sort and shuffle phase of MapReduce?
A. Keys are presented to reducer in sorted order; values for a given key are not sorted.
B. Keys are presented to reducer in sorted order; values for a given key are sorted in ascending
order.
C. Keys are presented to a reducer in random order; values for a given key are not sorted.
D. Keys are presented to a reducer in random order; values for a given key are sorted in
ascending order.
 
Answer: A

6.Assuming default settings, which best describes the order of data provided to a reducer’s reduce
method:
A. The keys given to a reducer aren’t in a predictable order, but the values associated with those
keys always are.
B. Both the keys and values passed to a reducer always appear in sorted order.
C. Neither keys nor values are in any predictable order.
D. The keys given to a reducer are in sorted order but the values associated with each key are in
no predictable order
 
Answer: D

7.You wrote a map function that throws a runtime exception when it encounters a control character
in input data. The input supplied to your mapper contains twelve such characters totals, spread
across five file splits. The first four file splits each have two control characters and the last split has four control characters. Indentify the number of failed task attempts you can expect when you run the job with mapred.max.map.attempts set to 4:
A. You will have forty-eight failed task attempts
B. You will have seventeen failed task attempts
C. You will have five failed task attempts
D. You will have twelve failed task attempts
E. You will have twenty failed task attempts
 
Answer: E