Apache Storm interview questions

6. What is Bolts in Apache Storm?
All processing in topologies is done in bolts. Bolts can do simple stream transformations. Doing complex stream transformations often requires multiple steps and thus multiple bolts. Bolts can emit more than one stream. To do so, declare multiple streams using the declareStream method of OutputFieldsDeclarer and specify the stream to emit to when using the emit method on OutputCollector.

7. What are the advantages of using Apache Storm ?
Distributed real time processing
Stateless, Data is streamed
Stream abstraction
Micro batching processing

8. Explain the components of Apache Storm system?
Nimbus – This is a job tracker that distributes the code across clusters, computes the code and execute it.
Zookeeper – This is a mediator to communicate with the storm cluster.
Supervisor – It interacts with Nimbus with the help of zookeeper and executes the process as per the Nimbus’s instructions.

9. How many categories are there to define the stream grouping in Apache Storm?
Shuffle Grouping
Field Grouping
None Grouping
Local Grouping
Global Grouping
All Grouping
Direct grouping

10. Explain role of a zookeeper in Apache Storm?
Zookeeper is a mediator to facilitate coordination with clusters. Zookeeper is not involved in message passing, so workload on the zookeeper is very low.

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