NameNode and DataNode roles in Hadoop - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of NameNode in Hadoop

What is the primary responsibility of the NameNode in a Hadoop cluster?

A Executing MapReduce tasks on data nodes

B Storing the actual data blocks of files

C Handling network communication between clients and data nodes

D Managing the metadata and directory structure of the file system

💡 Hint

Think about which node keeps track of where files are stored.

The NameNode manages the metadata, such as file names, permissions, and locations of data blocks. It does not store actual data.

🧠 Conceptual

intermediate

Role of DataNode in Hadoop

Which of the following best describes the role of a DataNode in Hadoop?

A Stores the actual data blocks and serves read/write requests

B Manages the file system namespace and metadata

C Coordinates job scheduling and resource allocation

D Monitors network traffic between nodes

💡 Hint

Consider which node physically holds the data.

DataNodes store the actual data blocks and handle read/write requests from clients. They report back to the NameNode.

❓ data_output

advanced

DataNode Heartbeat Frequency

Given a Hadoop cluster where DataNodes send heartbeats every 3 seconds, how many heartbeats will a single DataNode send in 1 minute?

A 20

B 60

C 30

D 15

💡 Hint

Calculate how many 3-second intervals fit into 60 seconds.

60 seconds divided by 3 seconds per heartbeat equals 20 heartbeats.

❓ Predict Output

advanced

NameNode Metadata Access Simulation

What is the output of this Python code simulating NameNode metadata access counts?

Hadoop

metadata_access = {'file1': 5, 'file2': 3, 'file3': 7}
most_accessed = max(metadata_access, key=metadata_access.get)
print(most_accessed)

A 7

B file2

C file3

D file1

💡 Hint

max with key returns the key with the highest value.

The max function with key=metadata_access.get returns the key with the highest access count, which is 'file3' with 7 accesses.

🔧 Debug

expert

DataNode Block Report Error Identification

What error will this Python code raise when simulating a DataNode sending a block report with a missing key?

Hadoop

block_report = {'block1': 'OK', 'block2': 'OK'}
print(block_report['block3'])

A IndexError

B KeyError

C TypeError

D No error, prints None

💡 Hint

Accessing a dictionary with a missing key causes a specific error.

Accessing a dictionary with a key that does not exist raises a KeyError in Python.