Mutual Friends MapReduce Application

Motivation

Finding mutual friends is a compelling MapReduce App and has a nice write up on the web.

Background

Steve Krenzel Finding Friends

Code To Investigate

Account

class Account

getId()

getFriendIds()

AccountId

class AccountId

AccountIdSetIntersection

class MutualFriendIds

intersectWith(friendIds)

Code To Implement

class:	MutualFriendsMapper.java
methods:	map
package:	mapreduce.apps.friends.studio
source folder:	student/src/main/java

method: public void map(Account account, BiConsumer<OrderedPair<AccountId>, Set<AccountId>> keyValuePairConsumer) (sequential implementation only)

The only method you will need to alter is the map method. In this method, you will need to map every combination of the account holder to his/her friends. In order to do this, create ordered pairs of the given account’s ID and the IDs of the account holder’s friends. You must then feed each individual ordered pair into the keyValuePairConsumer along with the full set of the account holder’s friends.

Hint: check out the methods in the Account class for help.

class:	MutualFriendsClassicReducer.java
methods:	finisher
package:	mapreduce.apps.friends.studio
source folder:	student/src/main/java

method: public Function<List<Set<AccountId>>, MutualFriendIds> finisher() (sequential implementation only)

Investigate MutualFriendIds for clues on what you need to do.

Testing Your Solution

Correctness

class:	MutualFriendsStudioTestSuite.java
package:	mapreduce.apps.friends.studio
source folder:	testing/src/test/java