Hortonworks HDPCD 問題集

質問 1：
You need to run the same job many times with minor variations. Rather than hardcoding all job configuration options in your drive code, you've decided to have your Driver subclass org.apache.hadoop.conf.Configured and implement the org.apache.hadoop.util.Tool interface.
Indentify which invocation correctly passes.mapred.job.name with a value of Example to Hadoop?
A. hadoop setproperty mapred.job.name=Example MyDriver input output
B. hadoop setproperty ("mapred.job.name=Example") MyDriver input output
C. hadoop MyDrive -D mapred.job.name=Example input output
D. hadoop MyDriver mapred.job.name=Example input output
E. hadoop "mapred.job.name=Example" MyDriver input output
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 2：
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 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).
D. 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.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 3：
Determine which best describes when the reduce method is first called in a MapReduce job?
A. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The programmer can configure in the job what percentage of the intermediate data should arrive before the reduce method begins.
B. Reduce methods and map methods all start at the beginning of a job, in order to provide optimal performance for map-only or reduce-only jobs.
C. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The reduce method is called only after all intermediate data has been copied and sorted.
D. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The reduce method is called as soon as the intermediate key-value pairs start to arrive.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 4：
For each input key-value pair, mappers can emit:
A. One intermediate key-value pair, but of the same type.
B. As many intermediate key-value pairs as designed, but they cannot be of the same type as the input key-value pair.
C. As many intermediate key-value pairs as designed. There are no restrictions on the types of those key-value pairs (i.e., they can be heterogeneous).
D. One intermediate key-value pair, of a different type.
E. As many intermediate key-value pairs as designed, as long as all the keys have the same types and all the values have the same type.
正解：E
解説: (Topexam メンバーにのみ表示されます)

質問 5：
You want to populate an associative array in order to perform a map-side join. You've decided to put this information in a text file, place that file into the DistributedCache and read it in your Mapper before any records are processed.
Indentify which method in the Mapper you should use to implement code for reading the file and populating the associative array?
A. configure
B. combine
C. map
D. init
正解：A
解説: (Topexam メンバーにのみ表示されます)

質問 6：
What does the following command do? register '/piggyban):/pig-files.jar';
A. Invokes the user-defined functions contained in the jar file
B. Specifies the location of the JAR file containing the user-defined functions
C. Transforms Pig user-defined functions into a format that Hive can accept
D. Assigns a name to a user-defined function or streaming command
正解：B

質問 7：
To process input key-value pairs, your mapper needs to lead a 512 MB data file in memory. What is the best way to accomplish this?
A. Serialize the data file, insert in it the JobConf object, and read the data into memory in the configure method of the mapper.
B. Place the data file in the DataCache and read the data into memory in the configure method of the mapper.
C. Place the data file in the DistributedCache and read the data into memory in the map method of the mapper.
D. Place the data file in the DistributedCache and read the data into memory in the configure method of the mapper.
正解：B

質問 8：
Which one of the following files is required in every Oozie Workflow application?
A. job.properties
B. Config-default.xml
C. Workflow.xml
D. Oozie.xml
正解：C