CCD-410 Online Practice Questions and Answers
You have the following key-value pairs as output from your Map task:
(the, 1) (fox, 1) (faster, 1) (than, 1) (the, 1) (dog, 1)
How many keys will be passed to the Reducer's reduce method?
A. Six
B. Five
C. Four
D. Two
E. One
F. Three
What is the disadvantage of using multiple reducers with the default HashPartitioner and distributing your workload across you cluster?
A. You will not be able to compress the intermediate data.
B. You will longer be able to take advantage of a Combiner.
C. By using multiple reducers with the default HashPartitioner, output files may not be in globally sorted order.
D. There are no concerns with this approach. It is always advisable to use multiple reduces.
A client application creates an HDFS file named foo.txt with a replication factor of 3. Identify which best describes the file access rules in HDFS if the file has a single block that is stored on data nodes A, B and C?
A. The file will be marked as corrupted if data node B fails during the creation of the file.
B. Each data node locks the local file to prohibit concurrent readers and writers of the file.
C. Each data node stores a copy of the file in the local file system with the same name as the HDFS file.
D. The file can be accessed if at least one of the data nodes storing the file is available.
You have written a Mapper which invokes the following five calls to the OutputColletor.collect method:
output.collect (new Text ("Apple"), new Text ("Red") ) ;
output.collect (new Text ("Banana"), new Text ("Yellow") ) ; output.collect (new Text ("Apple"), new Text
("Yellow") ) ; output.collect (new Text ("Cherry"), new Text ("Red") ) ;
output.collect (new Text ("Apple"), new Text ("Green") ) ;
How many times will the Reducer's reduce method be invoked?
A. 6
B. 3
C. 1
D. 0
E. 5
A combiner reduces:
A. The number of values across different keys in the iterator supplied to a single reduce method call.
B. The amount of intermediate data that must be transferred between the mapper and reducer.
C. The number of input files a mapper must process.
D. The number of output files a reducer must produce.
In a MapReduce job with 500 map tasks, how many map task attempts will there be?
A. It depends on the number of reduces in the job.
B. Between 500 and 1000.
C. At most 500.
D. At least 500.
E. Exactly 500.
MapReduce v2 (MRv2/YARN) splits which major functions of the JobTracker into separate daemons? Select two.
A. Heath states checks (heartbeats)
B. Resource management
C. Job scheduling/monitoring
D. Job coordination between the ResourceManager and NodeManager
E. Launching tasks
F. Managing file system metadata
G. MapReduce metric reporting
H. Managing tasks
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 different Writable object time.
B. It returns a reference to a Writable object from an object pool.
C. It returns a reference to the same Writable object each time, but populated with different data.
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 if the next value is the same as the previous value, or a new Writable object otherwise.
Table metadata in Hive is:
A. Stored as metadata on the NameNode.
B. Stored along with the data in HDFS.
C. Stored in the Metastore.
D. Stored in ZooKeeper.
You need to move a file titled "weblogs" into HDFS. When you try to copy the file, you can't. You know you have ample space on your DataNodes. Which action should you take to relieve this situation and store more files in HDFS?
A. Increase the block size on all current files in HDFS.
B. Increase the block size on your remaining files.
C. Decrease the block size on your remaining files.
D. Increase the amount of memory for the NameNode.
E. Increase the number of disks (or size) for the NameNode.
F. Decrease the block size on all current files in HDFS.
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