Homework 1

Total points 7

Question 1 Which of the following is NOT a uniquely new trait of cloud computing problems compared to the previous generations of distributed systems problems? 1 point

• Large amounts of data

• On-demand access to cloud resources, with pay-as-you-go pricing

• Servers coordinating with each other

• New paradigms for storage like NoSQL storage systems

SOLUTION-Servers coordinating with each other

Question 2 A datacenter run by an upstart company called Zahoo! consumed about 1000 kWh in 2014. If only 500 kWh of this total power was used in running IT equipment (servers, routers, etc.), then the PUE of Zahoo’s datacenters is: 1 point

• 500

• 2.0

• 750

• 0.33

SOLUTION-

Question 3 The Hadoop Capacity Scheduler runs at: 1 point

• Map

• AM

• RM

• NM

SOLUTION-RM

Question 4If one of the machines in a Hadoop cluster is significantly faster than other machines in the cluster, then to reduce stragglers this fast machine should be assigned: 1 point

• The same number of containers as other machines

• More containers than other machines

• None of these options

• Fewer containers than other machines

SOLUTION-More containers than other machines

Question 5 In MapReduce, a difference between the Map and Reduce functions is: 1 point

• Both Map and Reduce process each input line separately.

• Both Map and Reduce process a set of all key-value pairs sharing the same key.

• Reduce processes a set of all key-value pairs sharing the same key, while Map processes each input line separately.

• Map processes a set of all key-value pairs sharing the same key, while Reduce processes each input line separately.

SOLUTION-Reduce processes a set of all key-value pairs sharing the same key, while Map processes each input line separately.

Question 6 Which of the following is a private cloud? 1 point

• Amazon Web Services Simple Storage Service

• Yahoo’s internal Grid clusters, accessible to only Yahoo employees

• Amazon Web Services Elastic Compute Cloud

• Microsoft Azure

SOLUTION-Yahoo’s internal Grid clusters, accessible to only Yahoo employees

Question 7 In MapReduce, one writes a program for Map that processes one input line at a time and outputs a (key, value) or nothing; and one writes a program for Reduce that processes an input of (key, all values for key). The iteration over input lines is done automatically by the MapReduce framework. You are given an input file containing information from an asymmetrical social network (e.g,. Twitter) about which users “follow” which other users. If user a follows b, the entry line is (a, b). In an input line, a and b are different from each other. You need to write a MapReduce program that outputs all pairs of users (a,b) who follow each other. Someone has written half of a MapReduce program where the shuffle traffic has key = (a,b), i.e., a pair of users. The Reduce function invoked on this key counts the number of occurrences of this key and if this count is 2, outputs the key as its final result.

You’re asked to write the Map function that takes as input (a,b) lines. The Map function should do the following: 1 point

• Output <key,value>= <(b,a),1>

• Output <key,value>= <(a,b),1>

• if (a<b) then output <key,value>= <(a,b),1>, otherwise output <key,value>= <(b,a),1>

• Output <key,value>= <(b,a),2>

SOLUTION-