Datastax Cassandra Administrator Certification Questions and Answer (Pratice Questions and Dumps)

Question-: Please arrange the below in order when a node is bootstrapped in Cassandra cluster?
A. Bootstrap node contact seed node
B. Seed node transfer info to joining node e.g. token ranges and cluster info
C. Streaming SSTables from cluster nodes to new node
D. Joining nodes state changes as normal node
E. New node start handling read/write request

Answer: A,B,C,D,E

Explanation: Bootstrapping means joining new node to the cluster. And while joining new node to the cluster following things happen.
A. New node which is bootstrapping node contact to the seed node.
B. Then Seed node transfer info to joining node e.g. token ranges and cluster info
C. All the nodes which needs to transfer the SSTables, will prepare those.
D. Existing node start streaming SSTables to new node. While transferring the SSTables existing node also serve the read/write request.
E. Once all the SSTable data streaming is done then Joining nodes state changes as normal node
F. New node start handling read/write request



Question-: Seed node is the same as coordinator node?
A. True
B. False

Answer: B

Explanation: In Cassandra cluster Seed node and Coordinator nodes are different things. Let’s learn about
1. Coordinator node : When you request read/write in the Cassandra cluster. The node you contacted become the coordinator node. It does not matter whether it has the data you requested or not. Because it is responsible for the read and write request. If node does not have data which you requested it get it from the node which has and then delivered. So any node in Cassandra cluster you connect become a coordinator node for that particular request.
2. Seed Nodes : These are yes, specially designated node. But not single point of failure or something. These are useful when you add a new node to the cluster. Then this new node has to know what is the current state of the Cluster. And that information can be provided by the seed nodes. Once seed nodes gives the Current cluster information to the bootstrapping node. Its job done. Hence, seed node are just to provide the Cluster info to new node joining the cluster.


Question-: When you add a new node to (v-node enabled) cluster. Token ranges are re-arranged. Which of the following would help in cleaning the data from existing node. Which is now taken care by new node?
A. You should run “nodetool compact� command on the source node and neighboring nodes that shared the same subrange after the new node is up and running.
B. You should run “nodetool clearnsnapshot� command on the source node and neighboring nodes that shared the same subrange after the new node is up and running.
C. You should run “nodetool cleanup� command on the source node and neighboring nodes that shared the same subrange after the new node is up and running.
D. You should run “nodetool repair� command on the source node and neighboring nodes that shared the same subrange after the new node is up and running.
E. You don’t have to do anything. Cassandra would automatically manages and reshuffle the data.

Answer: C

Explanation: When you add a new node to the cluster. Then token ranges should re-arrange and new node should start handling the read-write request as per the its own token range. Once bootstrapping is completed (means new node joined up and running) then old node which were having the data (which are not belong to this node) should be cleaned. And than can be easily done using the “nodetool cleanup� process on the source node and neighboring nodes. This command helps in preventing the database from including the old data to rebalance the load on that node. When you use this command temporarily it increases the disk space and higher Disk I/O possible.
Remember you don’t have to run the nodetool cleanup command on the new node. But rather the source node and neighboring nodes.

Related Questions

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Question-: Which of the following statement is correct with regards to write consistency?
A. Write to first replica and the replica crashes one second later. The other messages are not delivered. The data is lost.
B. Write to first replica and the operation times out. Future reads can return the old or the new value. You will not know the data is incorrect.
C. Write to first replica and one of the other replicas is down. The node comes back online. The application will get old data from that node until the node gets the correct data or a read repair occurs.
D. Write at QUORUM and then a read at QUORUM. One of the replicas dies. You will always get the correct data.


Question-: Which of the following is correct for transactions in Cassandra?
A. Cassandra offers atomic, isolated and durable transaction with eventual and tunable consistency.
B. Cassandra does not support consistency in ACID sense.
C. Cassandra support atomicity and isolation at row-level.
D. Inserts or updates of more than two rows in the same partition are treated as one write operation.
E. Delete operation is not atomic at partition level.


Question-: Suppose you have setup the consistency level as QUORUM with the replication factor as , which of the following statements are correct?
A. Database replicates the write to all nodes in the cluster and waits for acknowledgement from two nodes.
B. If the write fails on one node and succeeds on another node, Cassandra will repot as a failure.
C. If the write fails on one node and succeeds on another node, then replicated write that succeeds on the other node will be rolled back.
D. If the write fails on one node and succeeds on another node, then replicated write that succeeds on the other node will not be rolled back.


Question-: Which of the following statements are correct with regards to Isolation in Cassandra database?
A. A write to a row within a single partition on a single node is only visible to the client performing the operation.
B. A write to a row within a single partition on a single node is visible to all the client connecting to the database.
C. All updates in a batch operation belonging to a given partition key on a single node is only visible to the client performing the operation.
D. All updates in a batch operation belonging to a given partitions keys on a multiple node is not isolated.


Question-: Which of the following is a valid statement with regards to Gossip protocol, in Cassandra database setup?
A. You should setup every node as a seed node for better performance in the cluster and each node well aware about each other in ring.
B. You should use the same list of seed nodes for each node in the cluster.
C. Seed node is only single point of failure in the Cassandra cluster setup. Hence, you should have more than one node setup as a seed node.
D. To permanently change a node’s membership in a cluster, you must explicitly add or remove nodes from the cluster.


Question-: What all the benefits of the defining v-nodes or converting a physical node into multiple v-nodes in the Cassandra Cluster?
A. With v-nodes tokens are automatically calculated for each v-node and assigned accordingly.
B. While adding and removing nodes cluster automatedly balance the cluster and load would be evenly distributed across the nodes.
C. When new node is added in the cluster can be build faster, because every node share the load of building this new node.
D. The proportion of vnodes assigned to each machine in a cluster can be assigned, so smaller and larger nodes can be used in the cluster.