Cloudera Certified Developer for Apache Hadoop (CCDH) 認定 CCD-410 試験問題:

1. What is the disadvantage of using multiple reducers with the default HashPartitioner and distributing your workload across you cluster?

A) There are no concerns with this approach. It is always advisable to use multiple reduces.
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) You will not be able to compress the intermediate data.

2. You write MapReduce job to process 100 files in HDFS. Your MapReduce algorithm uses TextInputFormat: the mapper applies a regular expression over input values and emits key-values pairs with the key consisting of the matching text, and the value containing the filename and byte offset. Determine the difference between setting the number of reduces to one and settings the number of reducers to zero.

A) With zero reducers, no reducer runs and the job throws an exception. With one reducer, instances of matching patterns are stored in a single file on HDFS.
B) With zero reducers, instances of matching patterns are stored in multiple files on HDFS. With one reducer, all instances of matching patterns are gathered together in one file on HDFS.
C) There is no difference in output between the two settings.
D) With zero reducers, all instances of matching patterns are gathered together in one file on HDFS. With one reducer, instances of matching patterns are stored in multiple files on HDFS.

3. What is a SequenceFile?

A) A SequenceFile contains a binary encoding of an arbitrary number of heterogeneous writable objects.
B) A SequenceFile contains a binary encoding of an arbitrary number of homogeneous writable objects.
C) A SequenceFile contains a binary encoding of an arbitrary number of WritableComparable objects, in sorted order.
D) A SequenceFile contains a binary encoding of an arbitrary number key-value pairs. Each key must be the same type. Each value must be same type.

4. MapReduce v2 (MRv2/YARN) splits which major functions of the JobTracker into separate daemons? Select two.

A) Managing file system metadata
B) MapReduce metric reporting
C) Job scheduling/monitoring
D) Resource management
E) Job coordination between the ResourceManager and NodeManager
F) Managing tasks
G) Launching tasks
H) Heath states checks (heartbeats)

5. 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) Four
B) Five
C) Six
D) Two
E) Three
F) One

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