Top 20 Apache Oozie Interview Questions – Analytics

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This article was published as a part of the Data Science Blogathon.

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introduction

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Apache Oozie is a Hadoop workflow scheduler. It is a system that manages the workflow of dependent tasks. Users can design directed acyclic graphs of workflows that can be run parallely and sequentially in Hadoop.

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Image: https://oozie.apache.org/

Apache Oozie is an important topic in data engineering so we will discuss some Apache Oozie Interview Questions and Answers. These questions and answers will help you prepare for Apache Oozie and Data Engineering Interview.

Read more about Apache Oozie here.

Interview Questions on Apache Oozie

1. What is Oozie?

Oozie is a Hadoop workflow scheduler. Oozie allows users to design directed acyclic graphs of workflows, which can then be run in parallel or sequentially in Hadoop. It can also execute regular Java classes, Pig operations, and interface with HDFS. It can run tasks both sequentially and concurrently.

2. Why do we need Apache Oozie?

Apache Oozie is an excellent tool for managing multiple tasks. There are many types of tasks that users may want to schedule to run at a later time, as well as tasks that must be executed in a specified order. Apache Oozie can make this type of execution very easy. Using Apache Oozie, administrators or users can perform multiple independent tasks in parallel, run tasks in a specific order, or control them from anywhere, making it extremely helpful.

3. What type of application is Oozie?

Oozie is a Java web app that runs in a Java Servlet container.

4. What exactly is the Application Pipeline in Oozie?

It is important to add workflow jobs that run regularly but at different times. Several successive executions of a process become the input for the following workflow. When these processes are linked together, the result is referred to as a data application pipeline.

5. What is the workflow in Apache Oozie?

Apache Oozie is a set of workflow actions that includes Hadoop MapReduce jobs, Pig jobs, etc. Activities are organized in a Control Dependency DAG (Direct Acyclic Graph) that controls how and when they can be executed. hPDL, an XML process definition language, defines Oozie workflows.

6. What are the Key Elements of the Apache Oozie Workflow?

There are two main components to the Apache Oozie workflow.

Control Flow Nodes: These nodes are used to define the start and end of the workflow as well as control the execution path of the workflow. Action nodes are used to initiate processing or computation tasks. Oozie Hadoop supports MapReduce, Pig, and file system operations and system-specific activities such as HTTP, SSH, and email.

7. What are the functions of Join and Fork nodes in Oozie?

In Oozie, fork and join nodes are used in tandem. The fork node splits the execution path into multiple concurrent paths. A join node joins two or more concurrent execution routes into one. The descendants of the join node are fork nodes that join concurrently as join nodes.

syntax:

<कांटा नाम = "[FORK-NODE-NAME]">

<पथ प्रारंभ = "[NODE-NAME]" / >

,

<पथ प्रारंभ = "[NODE-NAME]" / >

,

<नाम में शामिल हों = "[JOIN-NODE-NAME]"से ="[NODE-NAME]" / >

8. What are the Different Control Nodes in Oozie Workflow?

There are various control nodes:

Start and Kill Decision Fork and Join Control Nodes

9. How can I set the start, end and error nodes for Oozie?

This can be done in the following syntax:

,[A custom message],

10. What exactly is the application pipeline in Oozie?

It is important to add workflow jobs that run regularly but at different times. Several successive executions of a process become the input for the following workflow. When these processes are linked together, the result is referred to as a data application pipeline.

11. What are Control Flow Nodes?

The mechanisms that specify the start and end of the process are known as control flow nodes (start, end, fail). In addition, control flow nodes give way to control the execution path (decision, fork, and join) of the workflow.

12. What are Action Nodes?

The mechanism that initiates the execution of the computation/processing task is called the action node. Oozie supports a wide variety of Hadoop actions out of the box, including Hadoop MapReduce, Hadoop File System, Pig, and others. In addition, Oozie supports system-specific jobs such as SSH, HTTP, email, etc.

13. Are cycles supported by the Apache Oozie workflow?

Apache Oozie does not support workflow cycles. Workflow definitions in Apache Oozie must be a strict DAG. If Oozie Workflow detects a cycle in the workflow specification during application deployment, the deployment is aborted.

14. What is the use of Oozie Bundle?

Oozie Bundle enables the user to run jobs in batches. Oozie bundled tasks are started, paused, suspended, restarted, re-run, or killed in batches, giving you more operational control.

15. How does pipeline work in Apache Oozie?

Pipelines in Oozie help integrate multiple jobs into a workflow that runs regularly but at varying intervals. The output of multiple workflow executions becomes the input to the next planned task in the workflow, which is conducted back to back in the pipeline. A connected series of workflows make up the Oozie pipeline of jobs.

16. Explain the role of coordinator in Apache Oozie?

To solve trigger-based workflow execution, the Apache Oozie Coordinator is employed. It provides an infrastructure to provide triggers or forecasts, after which it schedules workflows based on those established triggers. It enables administrators to monitor and regulate workflow execution in response to cluster conditions and application-specific constraints.

17. What is the function of Decision Node in Apache Oozie?

Switch statements are decision nodes that perform various operations dependent on the conclusion of another expression.

18. What are the various control flow nodes provided by the Apache Oozie workflow to start and end the workflow?

The following control flow nodes are supported by Apache Oozie workflows and start or stop workflow execution.

Start Control Node – The Start Node is the starting node to which the Oozie Workflow task is transferred and acts as the entry point to the Workflow Task. A start node is required for each Apache Oozie workflow definition. Last Control Node – The last node is the last node to which the Oozie workflow task is transferred, indicating that the workflow task was completed. When a workflow task reaches the last node, it is completed, and the task status is switched to SUCCEED. An end node is required for each Apache Oozie workflow definition. The Kill Control node allows the workflow job to kill itself. When a workflow task reaches the kill node, it ends in error, and the status of the task changes to KILLED.

19. What are the various control flow nodes that Apache Oozie workflows offer to control the workflow execution path?

The following control flow nodes are supported by the Apache Oozie workflow and control the execution path of the workflow.

Decision Control Node – A decision control node is similar to a switch-case statement as it allows a process to choose which execution path to take. Join the fork and control nodes – the fork and control nodes work in pairs and act as follows. The fork node splits a single execution path into multiple concurrent execution paths. The join node waits until all concurrent execution paths have arrived from the corresponding fork node.

20. What is the default database used by Oozie to store Job ID and Status?

Oozie stores the job ID and job status in the Derby database.

conclusion

These Apache Oozie Interview Questions can help you prepare for the interview for your upcoming Personal Interview. In interviews related to Oozie, interviewers usually ask the interviewer these.

to sum up:

Apache Oozie is a distributed scheduling system for launching and managing Hadoop tasks. Oozie allows you to combine multiple complex tasks that are executed in a specific order to complete a larger task. Two or more jobs within a specific set of tasks can be programmed to execute in parallel with Oozie.

The real reason for adopting Oozie is to manage the variety of tasks that are being handled in Hadoop systems. The user specifies the various dependencies between jobs in the form of the DAG. This information is consumed by Oozie and handled in the order specified in the workflow. It saves the time of the user while managing the entire workflow. Oozie also determines the frequency at which a task is executed.

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