Introduction

Apache Oozie is a scheduler framework utilised to run and oversee Hadoop jobs in an appropriated environment. Oozie underpins consolidating various complex jobs that run in a specific request for achieving an important task. With Oozie, inside a specific task arrangement, at least two jobs can be modified to run in equal.

The motivation behind why Oozie is being utilised so much is that it is pleasantly incorporated with the Hadoop stack that underpins a few Hadoop Oozie jobs, for example, Sqoop, Hive, and Pig, alongside other frameworks explicit undertakings, like Java and Shell.

  1. How does Oozie work?
  2. Example Workflow Diagram
  3. Packaging and deploying an Oozie workflow application
  4. What is Oozie used for?
  5. Features of Oozie
  6. Apache Oozie Coordinator 

1. How does Oozie work?

Since you know ‘What is Oozie?’, how about we perceive how Oozie works.

Service in the cluster is run by Oozie, and users submit work process definitions for quick or later handling. 

Oozie workflow process comprises control-flow nodes and action nodes. 

An action node addresses a work process task, e.g., moving documents into Hadoop Distributed File System, running a shell script, Hive or Pig jobs, running a MapReduce or bringing in data utilising Sqoop of a program written in Java. 

The work process execution between activities by permitting builds like contingent logic wherein various branches might be followed relying upon the consequence of a previous activity node is controls by the control-flow node.

Start (Begin) Node, Error (Kill) Node, and End (Success) Node fall under this class of nodes. 

  1. Start (Begin) Node, assigns the beginning of the work process job.
  2. Error (Kill) Node assigns the event of an error and comparing the error message to be printed.
  3. End (Success) Node signals the end of the job.

Toward the end of the execution of a work process, a Hypertext Transfer Protocol call-back is utilised by Oozie to refresh the user with the work process status. Likewise, trigger the call-back is by entry-to or exit from an action node.

2. Example Workflow Diagram

Oozie workflow example or Oozie example:

      Begin                          Success

Start à   MapReduce Program   à  End

            Error           

                              Kill

            Unsuccessful Termination

Apache Oozie architecture or Oozie architecture:

                    HTTP

Oozie Client  à  Oozie Server  à  Hadoop Cluster

                            ↓

                      SQL DB

3. Packaging and deploying an Oozie workflow application

A workflow application comprises the workflow description and every one of the related resources, for example, Pig scripts, Jar files, MapReduce and so on. The straightforward directory structure is followed by applications need and are conveyed to Hadoop Distributed File System with the goal that Oozie can get to them.

It is important to keep workflow.xml in the high-level directory. Lib directory includes Jar files, including MapReduce classes. Work process application adjusting to this design can be worked with any form device, e.g., Maven or Ant. Such a form should be replicated to Hadoop Distributed File System utilising a command.

Step-by-step for consecutive an Oozie workflow job:

In this part, we will perceive how to run a workflow job. To run this, we will utilise the Oozie command line apparatus.

  1. Export OOZIE_URL context variable, which represents the Oozie command.
  2. Run the workflow job.
  3. Get the situation with the workflow job.
  4. The consequences of fruitful execution workflow can be seen utilising the Hadoop command.

4. What is Oozie used for?

The real rationale of utilising Oozie is for dealing with a few sorts of jobs that are being handled in the Hadoop framework.

As DAG or Directed Acyclic Graphs, a few conditions in the middle of jobs are indicated by the client. This data is devoured by Oozie and is dealt with in a specific request as present in the workflow. By doing this, the client’s ideal opportunity for dealing with the whole workflow is saved. Alongside that, Oozie indicates the recurrence of the performance of a job.

5. Features of Oozie

  1. User Application Programming Interface, just as a command-line interface, is available in Oozie that can be utilised for monitoring, controlling, and launching a task from the Java application.
  2. Email notices can be sent after the fulfilment of jobs.
  3. The execution of jobs, which are booked for running occasionally, is conceivable with the Oozie framework.
  4. Utilising Web Service Application Programming Interfaces, jobs can be controlled from anyplace.

6. Apache Oozie Coordinator 

There is some workflow that should be routinely planned, and there is some workflow that is unpredictable to plan. The two sorts of the workflow can be immediately designed by utilising the Oozie Coordinator. 

Here is a portion of the definition one requirements to comprehend for the organiser jobs: 

  1. Frequency: For the job execution, frequency is referenced, and it is included in minutes.
  2. End: It alludes to the job’ end date-time.
  3. Start: It alludes to the job’s beginning date-time.
  4. Time zone: This educates us regarding the facilitator application’s time zone.

Conclusion

Oozie is utilised for setting off the work process activities that utilization the Hadoop execution engine for executing different assignments. Oozie uses the present-day Hadoop hardware for load balancing, failover, and so on. Oozie is answerable for identifying the fulfilment of tasks by call-back and polling.

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