Oozie is the workflow that helps in the execution of Hadoop jobs. The jobs can be scheduled for the execution later, monitored, and handled from anywhere. Go through these Apache Oozie Interview Questions and increase your chances of getting selected.
If you are making a career in Oozie and preparing for the interview, then read these Apache Oozie Interview Questions as it will help you in revising your Oozie concepts in the right manner. Apache Oozie is a scheduler system that helps in the execution of Hadoop jobs. The action nodes and control flow nodes make up the complete workflow of Apache Oozie.
The Apache Oozie Interview Questions given in this article will help you clear your concepts related to Oozie. If you want to learn more about apache Oozie, then do not worry as we offer courses too that you can apply for and make your concepts clear along with building your skills.
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Question 1: Explain the Apache Oozie
Apache Oozie is a scheduler that lets users schedule and executes Hadoop jobs. Users can execute multiple tasks parallelly so that more than one job can be executed simultaneously. It is a scalable, extensible, and reliable system that supports different types of Hadoop jobs. These jobs include MapReduce jobs, Hive, Streaming jobs, Scoop, and Pig.
Question 2: What is the need for Apache Oozie?
Apache Oozie provides a great way to handle multiple jobs. There are different types of jobs that users want to schedule to be run later or the tasks that need to follow a specific sequence during execution. These kinds of executions can be made easy with the help of Apache Oozie. Using Apache Oozie, the administrator or the user can execute the various independent jobs parallelly, run the jobs back to back following a certain sequence, or can control the jobs from anywhere thus, making it very useful.
Question 3: What are the main components of the Apache Oozie workflow?
The Apache Oozie workflow consists of the control flow nodes and action nodes.
Below is the explanation of these nodes:
- Control flow nodes: These nodes define the start and end of the workflow, i.e., start, end, and fail. Besides, it also offers the mechanism that manages the execution path in the workflow, i.e., decision, fork, and join.
- Action nodes: These nodes offer the mechanism that initiates the execution of the processing or computation task. Oozie supports different actions, including Hadoop MapReduce, Pig, and File system, and system-specific jobs such as HTTP, SSh, and email.
Question 4: What is the use of Join and Fork nodes in Oozie?
The fork and join nodes in Oozie get used in pairs. The fork node splits the execution path into many concurrent execution paths. The join node joins the two or more concurrent execution paths into a single one. The join node is the children of the fork nodes that concurrently join to make join nodes.
Question 5: What are some of the useful EL functions in the Oozie workflow?
Below is the list of some useful EL functions of Oozie workflow:
- wf: name() – It returns the application name in the workflow.
- wf: id() – This function returns the job id of the currently running workflow job.
- wf:errorCode(String node) – It returns the error code of the executing action node.
- wf:lastErrorNod() – This function returns the name of the last executed action node in a workflow that exits with an error.
Question 6: Explain the different nodes supported in Oozie workflow.
Below is the list of action nodes that Apache Oozie workflow supports in and helps in the computation tasks:
- Map Reduce Action: This action node initiates the Hadoop Map-Reduce job
- Pig Action: This node is used to start the Pig job from Apache Oozie workflow.
- FS (HDFS) Action: This action node allows the Oozie workflow to manipulate all the HDFS-related files and directories. Also, it supports commands such as mkdir, move, chmod, delete, chgrp, and touchz.
- Java Action: It is the sub-workflow action node that helps in the execution of public static void main(String args) method of main java class in Oozie workflow.
Question 7: What is Oozie Bundle?
Oozie bundle allows the user to execute the job in batches. The Oozie bundle jobs are started, stopped, suspended, resumed, re-run, or killed in batches, thus providing better operational control.
Question 8: Explain the Pipeline works In Oozie
The pipeline in Oozie helps in connecting the multiple jobs in a workflow that executes regularly but during different intervals. In this pipeline, the output of multiple executions of workflow becomes the input of the next scheduled job in the workflow that gets executed back to back in the pipeline. The joined chain of workflows forms the Oozie pipeline of jobs.
Question 9: Explain the life cycle of the Oozie workflow job
The job in the Apache Oozie workflow transition through the blow states:
- PREP – This is the state when the user creates the workflow job. During PREP state, the job is only defined and is not running.
- RUNNING – When the job starts, it changes to the RUNNING state and remains in this state until the job reaches the end state, an error occurs, or the job is suspended.
- SUSPENDED – The state of the job in Oozie workflow changes to SUSPENDED if the job is suspended in between. The job will remain in this state until it is killed or resumed.
- SUCCEEDED – The workflow job becomes SUCCEEDED when the job reaches the end node.
- KILLED – The workflow job transitions to KILLED state when the administrator kills any job in PREP, RUNNING OR SUSPENDED states
- FAILED – The job state changes into a FAILED state when the running job fails due to an unexpected error.
These Apache Oozie Interview Questions will be helpful to you in making you interview-ready for your next personal interview. These are the questions that interviewers ask very frequently to the interviewee in Oozie-related interviews. You must have a look at these Apache Oozie interview questions before appearing for an interview as these questions will help you in the revision of the concepts and boost your confidence.
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