CASSANDRA Operations and Administration

Question 1

What does 'nodetool repair' do in Cassandra?

Accepted Answer

Synchronizes replicas by comparing and streaming missing data between nodes

Answer

nodetool repair compares replica sets using Merkle trees and streams any missing or out-of-date data to bring all replicas into sync.

Question 2

What does the 'nodetool drain' command do before a node shutdown?

Accepted Answer

Flushes all MemTables, stops accepting writes, and drains the CommitLog so the node can be safely stopped

Answer

nodetool drain ensures all pending writes are flushed to SSTables and the CommitLog is cleared, allowing a clean node shutdown without data loss.

Question 3

What does 'nodetool cleanup' do after adding a new node to a Cassandra cluster?

Accepted Answer

Deletes data from existing nodes that no longer falls within their token ranges after rebalancing

Answer

After a new node joins and data streams to it, nodetool cleanup removes the portions of data on existing nodes that the new node now owns.

Question 4

What is the purpose of 'nodetool rebuild' command?

Accepted Answer

Streams data for all token ranges from a specified data center, used when adding a new DC

Answer

nodetool rebuild streams the current data for the node's token ranges from another data center, used to populate a new DC without running a full repair.

Question 5

How can you monitor Cassandra metrics using industry-standard monitoring tools?

Accepted Answer

Cassandra exposes metrics via JMX, which can be scraped by tools like Prometheus via a JMX exporter

Answer

Cassandra exposes hundreds of metrics via JMX (Java Management Extensions), and tools like the Prometheus JMX Exporter or Datadog Agent can scrape and forward them.

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA Operations and Administration