A. Be a subclass of FileInputFormat.

B. Implement WritableComparable.

C. Implement a comparator for speedy sorting.

D. Override isSplitable.

E. Implement a splittable compression algorithm.

A. The input file is split exactly at the line breaks, so each RecordReader will read a series of complete lines.

B. Input file splits may cross line breaks. A line that crosses file splits is ignored.

C. Input file splits may cross line breaks. A line that crosses file splits is read by the RecordReader of the split that contains the end of the broken line.

D. Input file splits may cross line breaks. A line that crosses file splits is read by the RecordReader of the split that contains the beginning of the broken line.

E. Input file splits may cross line breaks. A line that crosses file splits is read by the RecordReaders of both splits containing the broken line.

A. Yes, because Java is a polymorphic object-oriented language and thus reducer code can be reused as a combiner.

B. No, because the sum operation in the reducer is incompatible with the operation of a Combiner.

C. Yes, because the sum operation is both associative and commutative and the input and output types to the reduce method match.

D. No, because the Combiner is incompatible with a mapper which doesn't use the same data type for both the key and value.

E. No, because the Reducer and Combiner are separate interfaces.

A. Package your code and the Apache Commands Math library into a zip file named JobJar.zip

B. Have your system administrator copy the JAR to all nodes in the cluster and set its location in the HADOOP_CLASSPATH environment variable before you submit your job.

C. When submitting the job on the command line, specify the -libjars option followed by the JAR file path.

D. Have your system administrator place the JAR file on a Web server accessible to all cluster nodes and then set the HTTP_JAR_URL environment variable to its location.

A. Always. The point of a combiner is to serve as a mini-reducer directly after the map phase to increase performance.

B. Never. Combiners and reducers must be implemented separately because they serve different purposes.

C. When the types of the reduce operation's input key and input value match the types of the reducer's output key and output value and when the reduce operation is both communicative and associative.

D. When the signature of the reduce method matches the signature of the combine method.

E. Always. Code can be reused in Java since it is a polymorphic object-oriented programming language.

A. HTML

B. Avro

C. JSON

D. CSV

E. SequenceFiles

F. XML