Developing Distributed Applications Using ZooKeeper Cognitive Class Exam Quiz Answers

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Introduction to Developing Distributed Applications Using ZooKeeper

Apache ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and group services. It’s designed to be robust, highly available, and efficient, making it ideal for coordinating distributed applications.

Key Concepts

1. Znodes: Znodes are like files or directories in a file system. They store data and can also have children znodes. Znodes are identified by a path, similar to file paths in a file system.
2. Data Model: ZooKeeper provides a hierarchical namespace, where each node (znode) can store a small amount of data (up to 1MB). Applications can read from and write to these znodes.
3. Watchers: Watchers are event notifications that clients can set on znodes. They allow clients to receive notifications when the state of a znode changes. Watchers are one-time triggers, so they need to be set each time you want to be notified of changes.
4. Consistency Guarantees: ZooKeeper provides strong consistency guarantees. Once a write operation is acknowledged, all clients will see the same view of the data.
5. Sessions: Clients connect to ZooKeeper using sessions. Sessions are associated with timeouts, and clients need to handle session expiry gracefully.

Getting Started

Setting Up ZooKeeper

1. Download and Installation: ZooKeeper can be downloaded from the Apache ZooKeeper website. Installation typically involves unpacking the distribution and configuring zoo.cfg.
2. Configuration: zoo.cfg file needs to be configured to specify important details such as data directory, client ports, and ensemble details if you’re setting up a cluster.

Using ZooKeeper in Your Application

1. Client Library: ZooKeeper provides client libraries for various programming languages (Java, Python, etc.). Include the relevant client library in your project.
2. Connecting to ZooKeeper: Connect to ZooKeeper ensemble using the ZooKeeper class in your chosen language’s library. Specify the connection string (comma-separated list of host).
3. CRUD Operations: Use the client library to perform CRUD operations on znodes (create, read, update, delete).
4. Watchers: Set watchers on znodes to receive notifications of changes.
5. Error Handling: Handle errors gracefully, especially network issues and session timeouts.

Best Practices

• Keep Data Small: Znodes should ideally store small amounts of data (up to 1MB).
• Watchers: Use watchers judiciously to minimize overhead and ensure proper handling of events.
• Error Handling: Implement robust error handling and retry mechanisms to handle transient failures.

Conclusion

ZooKeeper simplifies the complexity of building distributed systems by providing a reliable and efficient way to manage coordination tasks. By understanding its core concepts and integrating them into your applications, you can leverage ZooKeeper to build scalable and reliable distributed systems effectively.

Developing Distributed Applications Using ZooKeeper Cognitive Class Certification Answers

Module 1 – Introduction Zookeeper Quiz Answers

Question 1: What is NOT a benefit that distributed systems offer over centralized systems?

• Price to achieve redundancy
• Redundancy
• Ease of developing your own coordination service
• Scalability

Question 2: A ZooKeeper client can perform a read operation from any server in the ensemble, but a write operation must go through the ZooKeeper leader and requires a majority consensus to succeed. True or false?

• False
• True

Question 3: What’s the benefit of running ZooKeeper in Standalone mode over Replicated mode?

• Cheaper
• Resilience
• Simpler testing and learning
• High availability

Module 2 – The Zoookeeper Data Model Quiz Answers

Question 1: Which of the following statements is true?

• A client reading the data stored at a znode can receive some of the data.
• ZooKeeper is designed for high-volume storage.
• The path to a znode must be expressed as a canonical, absolute, and slash-separated path.
• Znodes can be used to store data that exceeds 1MB.

Question 2: A znode can be in multiple states at the same time. True or false?

• False
• True

Question 3: Which of the following commands is used to retrieve the access control list of a znode?

• fetchACL
• setACL
• printACL
• getACL

Module 3 – Programming and Advance Topics Quiz Answers

Question 1: In addition to the 4 letter commands, JMX can be used to monitor ZooKeeper. True or false?

• False
• True

Question 2: Which two authentication plugins are included with ZooKeeper?

• ip and MD5
• ip and identify
• digset and MD5
• ip and digest

Question 3: What are the bindings that ZooKeeper comes with out of the box?

• Ruby and Java
• Java and C#
• Python and C
• Java and C

Developing Distributed Applications Using ZooKeeper Final Exam Answers

Question 1: What is the primary purpose of ZooKeeper in the Hadoop architecture?

• To provide logging support for Hadoop jobs
• To support the execution of workflows consisting of a collection of actions
• To provide a centralized coordination service for distributed applications
• To move data into HDFS

Question 2: When executing ZooKeeper in Replicated mode, a new leader can be elected if the former leader fails. True or false?

• True
• False

Question 3: Which of the following are consistency guarantees made by ZooKeeper? Select all that apply.

• Atomicity
• Reliability
• Timeliness
• Release

Question 4: ZooKeeper guarantees simultaneously consistent cross-client views. True or false?

• True
• False

Question 5: ZooKeeper can be used to implement several use cases including

• Leader Election
• Queue Management
• Configuration Management
• Locking
• All of the above

Question 6: A ZooKeeper client can maintain a list of servers to connect to, and the client will go through its list until it successfully connects to a ZooKeeper server. True or false?

• True
• False

Question 7: ZooKeeper Watches can be used to

• Watch for failed MapReduce jobs
• Watch for changes to Hadoop configuration
• Watch for changes in the Hadoop Filesystem (HDFS)
• None of the above

Question 8: If you want to be notified of a change in a ZooKeeper znode, you should use

• The ZooKeeper getData() method
• The ZooKeeper sync() method
• The ZooKeeper callback() method
• A ZooKeeper Watch

Question 9: In ZooKeeper, if you want a znode to be deleted when the client session ends, you should create a

• Session znode
• Ephemeral znode
• Temp znode
• Persistent znode

Question 10: Using the –s parameter when creating a znode results in a

• Ephemeral znode
• Sequential znode
• Temp znode
• Session znode
• Persistent znode

Question 11: Which of the ‘four letter word’ commands will show you the status of a ZooKeeper server?

• stat
• dump
• conf
• cons
• ruok

Question 12: When using the ZooKeeper Java API, what do you need to implement in order to receive Watcher notifications?

• A constructor that calls the watch method
• A class that inherits from zNode
• The process method of the Watcher interface
• None of the above

Question 13: In ZooKeeper, setting an ACL only pertains to the specific znode and is not recursive. True or false?

• True
• False

Question 14: In ZooKeeper, what permission do you need to have in order to change the ACL on a znode?

• READ
• ADMIN
• WRITE
• DELETE
• CREATE

Question 15: You can plug in your own authentication scheme rather than using the ones provided out of the box by ZooKeeper. True or false?

• True
• False