Cloudera CCD-410 Test Passed : Cloudera Certified Developer for Apache Hadoop (CCDH)

You want to perform analysis on a large collection of images. You want to store this data in HDFS and process it with MapReduce but you also want to give your data analysts and data scientists the ability to process the data directly from HDFS with an interpreted high-level programming language like Python. Which format should you use to store this data in HDFS?

• A. JSON
• B. HTML
• C. XML
• D. CSV
• E. SequenceFiles
• F. Avro

You are developing a MapReduce job for sales reporting. The mapper will process input keys representing the year (IntWritable) and input values representing product indentifies (Text).
Indentify what determines the data types used by the Mapper for a given job.

• A. The key and value types specified in the JobConf.setMapInputKeyClass and JobConf.setMapInputValuesClass methods
• B. The data types specified in HADOOP_MAP_DATATYPES environment variable
• C. The InputFormat used by the job determines the mapper's input key and value types.
• D. The mapper-specification.xml file submitted with the job determine the mapper's input key and value types.

Which describes how a client reads a file from HDFS?

• A. 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.
• B. 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.
• 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 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).

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. WritableComparable
• B. OutputFormat
• C. InputFormat
• D. Combiner
• E. Writable
• F. Partitioner

In the reducer, the MapReduce API provides you with an iterator over Writable values. What does calling the next () method return?

• A. It returns a reference to a Writable object from an object pool.
• B. It returns a reference to a different Writable object time.
• C. It returns a reference to the same Writable object if the next value is the same as the previous value, or a new Writable object otherwise.
• D. It returns a reference to a Writable object. The API leaves unspecified whether this is a reused object or a new object.
• E. It returns a reference to the same Writable object each time, but populated with different data.