VE572 —Methods and tools for big data Assignment 4 solved


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Ex. 1 — Processes and cgroups
1. Write a short summary describing what cgroups are.
2. Explain the differences and similarities between cgroups and processes in Linux.
Ex. 2 — MapReduce
In this exercise we write a MapReduce program to solve the second exercise from lab 3.
1. Write a Map class which extends the MapReduce Mapper class, extracts, and outputs pairs composed of a student ID and a grade.
Hint: read the file by line and tokenize each of them using StringUtils.
2. Write a Reduce class which extends the MapReduce Reducer class, outputs pairs composed of a
student ID and its highest grade.
Hint: use Iterable to iterate over all the values of a given key.
3. Write a driver function write set all the necessary properties to configure the MapReduce job.
Hint: specify what classes are to be used by the Mapper and Reducer, as well as where the input
and output files are located.
4. Run the MapReduce program and compare the running time to the streaming approach used in
the lab. Draw a table showing the comparison for various file sizes.
Ex. 3 — Avro
1. Install Avro.
2. Define a schema to represent an entry in the grade file generated in the second exercise of lab 3.
3. Write two short programs to serialize and de-serialize the grade file.
4. Explain the three ways into which Avro can be used in MapReduce, and when to apply each of
them. The three approaches are (i) mixed-mode, (ii) record-based, and (iii) key-value based.
Ex. 4 — Bloom filters
Sometimes it is appropriate to filter the data before running actions on it. For instance when referring
to exercise 2 of lab 3 we might only want to retrieve the maximum grade of the students whose ID ends
with a three. In that case one might want to use a preprocessing job to create a Bloom filter and use it
to filter out records in the mapper.
1. Describe what a Bloom filter is and how it works.
2. Using the BloomFilter class write a mapper which creates a Bloom filter.
3. Using Iterable combine all the Bloom filters together in the reducer and output
the result into a serialized Avro file.