Rack awareness in HDFS in Hadoop - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the rack ID for a DataNode in HDFS configuration.

Hadoop

dfs.datanode.hostname = [1]

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A/rack1/node1

Brack1-node1

Cnode1

D/rack1

Attempts:

3 left

💡 Hint

Common Mistakes

Using only node name without rack info

Omitting the leading slash in rack ID

The rack ID is specified as a path-like string such as '/rack1/node1' to indicate the rack and node location.

2fill in blank

medium

Complete the code to import the class used for rack awareness in HDFS Java code.

Hadoop

import org.apache.hadoop.net.[1];

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ARackAwareness

BRackPolicy

CRackResolver

DRackManager

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent classes like RackAwareness or RackManager

Confusing policy classes with resolver classes

The class RackResolver is used in Hadoop to resolve rack information for nodes.

3fill in blank

hard

Fix the error in the code to get the rack location of a DataNode using RackResolver.

Hadoop

String rack = RackResolver.[1](nodeName);

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AresolveRack

Bresolve

CgetRack

DgetRackLocation

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names that do not exist in RackResolver

Confusing method names with similar sounding ones

The correct method to get rack info is the static resolve() method on RackResolver.

4fill in blank

hard

Fill both blanks to create a rack-aware block placement policy object in HDFS.

Hadoop

BlockPlacementPolicy policy = new [1](conf, [2]);

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ABlockPlacementPolicyRackFaultTolerant

BBlockPlacementPolicyDefault

Cnull

DclusterMap

Attempts:

3 left

💡 Hint

Common Mistakes

Using default policy instead of rack-aware policy

Passing null instead of cluster map

The BlockPlacementPolicyRackFaultTolerant class is used for rack-aware placement, and it requires a clusterMap object as a parameter.

5fill in blank

hard

Fill all three blanks to create a dictionary mapping DataNodes to their rack locations.

Hadoop

Map<String, String> rackMap = new HashMap<>();
for (String node : nodes) {
    rackMap.put(node, [1].[2](node));
}
System.out.println(rackMap.[3]());

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ARackResolver

Bresolve

CkeySet

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names for rack resolution

Printing values instead of keys

We use RackResolver.resolve(node) to get rack info, and keySet() to print all node keys.