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Question 1

Single choice

Custom programmer-defined counters in MapReduce are:

A
Lightweight devices for bookkeeping within MapReduce programs.
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B
Lightweight devices for ensuring the correctness of a MapReduce program.Mappers Increment counters, and reducers decrement counters. If at the end of the program the counters read zero, then you are sure that the job completed correctly.
C
Lightweight devices for synchronization within MapReduce programs. You can use counters to coordinate execution between a mapper and a reducer.

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Correct answerA

Question 2

Single choice

Which process describes the lifecycle of a Mapper?

A
The JobTracker calls the TaskTracker s configure () method, then its map () method and finally its close () method.
B
The TaskTracker spawns a new Mapper to process all records in a single input split.
C
The TaskTracker spawns a new Mapper to process each key-value pair.
D
The JobTracker spawns a new Mapper to process all records in a single file.

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Correct answerC

Question 3

Single choice

You need to create a job that does frequency analysis on input data. You will do this by writing a Mapper that uses TextInputFormat and splits each value (a line of text from an input file) into individual characters.
For each one of these characters, you will emit the character as a key and an InputWritable as the value.
As this will produce proportionally more intermediate data than input data, which two resources should you

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A
Processor and network I/O
B
Disk I/O and network I/O
C
Processor and RAM
D
Processor and disk I/O

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Correct answerB

Question 4

Single choice

Which best describes what the map method accepts and emits?

A
It accepts a single key-value pair as input and emits a single key and list of corresponding values as output.
B
It accepts a single key-value pairs as input and can emit only one key-value pair as output.
C
It accepts a list key-value pairs as input and can emit only one key-value pair as output.
D
It accepts a single key-value pairs as input and can emit any number of key-value pair as output, including zero.

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Correct answerD

Question 5

Single choice

What is the behavior of the default partitioner?

A
The default partitioner assigns key value pairs to reducers based on an internal random number generator.
B
The default partitioner implements a round robin strategy, shuffling the key value pairs to each reducer in turn. This ensures an even partition of the key space.
C
The default partitioner computes the hash of the key.Hash values between specific ranges are associated with different buckets, and each bucket is assigned to a specific reducer.
D
The default partitioner computes the hash of the key and divides that value modulo the number of reducers. The result determines the reducer assigned to process the key-value pair.
E
The default partitioner computes the hash of the value and takes the mod of that value with the number of reducers. The result determines the reducer assigned to process the key value pair.
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Correct answerD

Question 6

Single choice

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

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Correct answerE

Question 7

Single choice

What happens in a MapReduce job when you set the number of reducers to zero?

A
No reducer executes, but the mappers generate no output.
B
No reducer executes, and the output of each mapper is written to a separate file in HDFS.
C
No reducer executes, but the outputs of all the mappers are gathered together and written to a single file in HDFS.
D
Setting the number of reducers to zero is invalid, and an exception is thrown.

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Correct answerB

Question 8

Single choice

The NameNode uses RAM for the following purpose:

A
To store the contents of files in HDFS.
B
To store filenames, list of blocks and other meta information.
C
To store the edits log that keeps track of changes in HDFS.
D
To manage distributed read and write locks on files in HDFS.

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Correct answerB

Question 9

Single choice

If you run the word count MapReduce program with m mappers and r reducers, how many output files will you get at the end of the job? And how many key-value pairs will there be in each file? Assume k is the number of unique words in the input files.

A
There will be r files, each with exactly k/r key-value pairs.
B
There will be r files, each with approximately k/m key-value pairs.
C
There will be r files, each with approximately k/r key-value pairs.
D
There will be m files, each with exactly k/m key value pairs.
E
There will be m files, each with approximately k/m key-value pairs.

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Correct answerA

Question 10

Single choice

Which of the following best describes the map method input and output?

A
It accepts a single key-value pair as input and can emit only one key-value pair as output.
B
It accepts a list of key-value pairs as input hut run emit only one key value pair as output.
C
It accepts a single key-value pair as input and emits a single key and list of corresponding values as output
D
It accepts a single key-value pair as input and can emit any number of key-value pairs as output, including zero.

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Correct answerD

Question 11

Single choice

Does the MapReduce programming model provide a way for reducers to communicate with each other?

A
Yes, all reducers can communicate with each other by passing information through the jobconf object.
B
Yes, reducers can communicate with each other by dispatching intermediate key value pairs that get shuffled to another reduce
C
Yes, reducers running on the same machine can communicate with each other through shared memory, but not reducers on different machines.
D
No, each reducer runs independently and in isolation.

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Correct answerD

Question 12

Single choice

Which best describes how TextInputFormat processes input files and line breaks?

A
Input file splits may cross line breaks. A line that crosses file splits is read by the Record Reader of the split that contains the beginning of the broken line.
B
Input file splits may cross line breaks. A line that crosses file splits is read by the Record Readers of both splits containing the broken line.
C
The input file is split exactly at the line breaks, so each Record Reader will read a series of complete lines.
D
Input file splits may cross line breaks. A line that crosses file splits is ignored.
E
Input file splits may cross line breaks. A line that crosses file splits is read by the RecordReader of the split that contains the end of the broken line.
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Correct answerE

Question 13

Single choice

You ve written a MapReduce job that will process 500 million input records and generated 500 million key-value pairs. The data is not uniformly distributed. Your MapReduce job will create a significant amount of intermediate data that it needs to transfer between mappers and reduces which is a potential bottleneck.
A custom implementation of which interface is most likely to reduce the amount of intermediate data transferred across the network?

A
Partitioner
B
OutputFormat
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C
WritableComparable
D
Writable
E
InputFormat
F
Combiner

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Correct answerF

Question 14

Single choice

In the standard word count MapReduce algorithm, why might using a combiner reduce the overall Job running time?

A
Because combiners perform local aggregation of word counts, thereby allowing the mappers to
process input data faster.
B
Because combiners perform local aggregation of word counts, thereby reducing the number of mappers that need to run.
C
Because combiners perform local aggregation of word counts, and then transfer that data to reducers without writing the intermediate data to disk.
D
Because combiners perform local aggregation of word counts, thereby reducing the number of key-value pairs that need to be snuff let across the network to the reducers.

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Correct answerA

Question 15

Single choice

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You want to send each line as one record to your Mapper. Which InputFormat should you use to complete the line: conf.setInputFormat (____.
class) ; ?

A
SequenceFileAsTextInputFormat
B
SequenceFileInputFormat
C
KeyValueFileInputFormat
D
BDBInputFormat

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Correct answerB

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