Oozie is a workflow scheduler system to manage Apache Hadoop jobs. It is integrated with the rest of the Hadoop stack supporting several types of Hadoop jobs such as Java MapReduce, Streaming MapReduce, Pig, Hive and Sqoop. Oozie is a scalable, reliable and extensible system. This technology is used in production at Yahoo!, running more than 200,000 jobs every day.
Features:
- Execute and monitor workflows in Hadoop
- Periodic scheduling of workflows
- Trigger execution of data availability
- HTTP and command line interface and web console
Workflow – Directed Acyclic Graph of Jobs:
Workflow Example:
<workflow-app nome='wordcount –wf’> <start to= ‘wordcount’/> <action name=’Wordcount'> <map-reduce> <job-tracker>foo.com:9001</job-tracker> <name-node>hdfs://bar.com:9000</name-node> <configuration> <property> <name>mapred.input.dir</name> <value>${inputDir}</value,> </property> <property> <name>mapred.output.dir</name> <value> ${outputDir}</value> </property> </configuration> </map-reduce> <ok to='end’/> <error to='kill'/> </action> <kill name='kill'/> <end name='end'/> </Workflow-app>
Workflow Definition:
A workflow definition is a DAG with control flow nodes or action nodes, where the nodes are connected by transitions arrows.
Control Flow Nodes:
The control flow provides a way to control the Workflow execution path. Flow control operations within the workflow applications can be done through the following nodes:
- Start/end/kill
- Decision
- Fork/join
Action Nodes:
- Map-reduce
- Pig
- HDFS
- Sub-workflow
- Java – Run custom Java code
Workflow Application:
Workflow application is a ZIP file that includes the workflow definition and the necessary files to run all the actions. It contains the following files:
- Configuration file – config-default.xml
- App files – lib/ directory with JAR and SO files
- Pig scripts
Application Deployment:
$ hadoop fs-put wordcount-wf hdfs://bar.com:9000/usr/abc/wordcount
Workflow Job Parameters:
$ cat job.properites Oozie.wf.application.path=hdfs://bar.com:9000/usr/abc/wordcount Input=/usr/abc/input-data Output=/usr/abc/output-data
Job Execution:
$ oozie job –run –config job.properties Job:1-20090525161321-oozie-xyz-W
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