MapReduce job execution flow in Hadoop - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the input format class in a MapReduce job configuration.

Hadoop

job.setInputFormatClass([1]);

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ATextInputFormat.class

BFileOutputFormat.class

CMapper.class

DReducer.class

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing input format with output format.

Using Mapper or Reducer classes instead of input format.

The input format class defines how input files are split and read. TextInputFormat is commonly used for text files.

2fill in blank

medium

Complete the code to set the number of reduce tasks in a MapReduce job.

Hadoop

job.setNumReduceTasks([1]);

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A0

B-1

C10

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting reduce tasks to zero when reduce phase is needed.

Using negative numbers which are invalid.

Setting the number of reduce tasks to 1 means the job will have one reducer. Zero means no reduce phase.

3fill in blank

hard

Fix the error in the code to correctly set the output key class for a MapReduce job.

Hadoop

job.setOutputKeyClass([1]);

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AText.class

BIntWritable.class

CTextInputFormat.class

DMapper.class

Attempts:

3 left

💡 Hint

Common Mistakes

Using input format or Mapper classes instead of data types.

Choosing a value class instead of key class.

The output key class defines the data type of the output keys. Text.class is commonly used for string keys.

4fill in blank

hard

Fill both blanks to set the output key class and output value class in a MapReduce job.

Hadoop

job.setOutputKeyClass([1]); job.setOutputValueClass([2]);

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AText.class

BIntWritable.class

CTextInputFormat.class

DMapper.class

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting mapper or format classes.

Wrong type for key/value (e.g., IntWritable for key).

The output key class is typically Text.class for strings (e.g., words), and output value class IntWritable.class for integers (e.g., counts) in jobs like word count.

5fill in blank

hard

Fill all three blanks to configure map output key class, value class, and combiner class in a MapReduce job.

Hadoop

job.setMapOutputKeyClass([1]); job.setMapOutputValueClass([2]); job.setCombinerClass([3]);

Drag options to blanks, or click blank then click option'

AText.class

BIntWritable.class

CReducer.class

DMapper.class

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing map output with final output classes.

Using Mapper.class for combiner.

Map output key Text.class, value IntWritable.class for intermediate data, combiner Reducer.class for local aggregation on map nodes.