Batch Applications for the Java Platform

2. Batch Applications for the Java Platform Arun Gupta, Java EE & GlassFish Guy blogs.oracle.com/arungupta @arungupta

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4. Batch Applications for the Java Platform • Standardizes batch processing for Java • Non-interactive, bulk-oriented, long-running • Data or computationally intensive • Sequentially or in parallel • Ad-hoc, scheduled or on-demand execution • Led by IBM • Spring Batch, WebSphere Compute Grid (WCG), z/OS Batch • Part of Java EE 7, can be used in Java SE

5. Batch Domain Language

6. Batch Domain Language

7. Batch Domain Language

8. Chunked Processing

9. Chunked Processing: Reader, Processor, Writer public interface ItemReader<T> { public void open(Externalizable checkpoint); public T readItem(); public Externalizable checkpointInfo(); public void close(); } public interface ItemProcessor<T, R> { public R processItem(T item); } public interface ItemWriter<T> { public void open(Externalizable checkpoint); public void writeItems(List<T> items); public Externalizable checkpointInfo(); public void close(); }

10. Batch Applications for the Java Platform Step Example using Job Specification Language (JSL) @Named(“accountReader") ...implements ItemReader... {public Account readItem() {// read account using JPA //For a job <step id=”sendStatements”> <chunk reader=”accountReader” processor=”accountProcessor” writer=”emailWriter” item-count=”10” /> </step> @Named(“accountProcessor") ...implements ItemProcessor... { public Statement processItems(Account account) {// read Account, return Statement @Named(“emailWriter") ...implements ItemWriter... { public void writeItems(List<Statements> statements) {// use JavaMail to send email

11. Checkpointing • For data intensive tasks, long periods of time • Checkpoint/restart is a common design requirement • Basically saves Reader, Writer positions • Naturally fits into Chunk oriented steps • reader.checkpointInfo() and writer.checkpointInfo() are called • The resulting Externalizable data is persisted • When the Chunk restarts, the reader and writer are initialized with the respective Externalizable data

12. Chunked Processing: Checkpoint public interface ItemReader<T> { public void open(Externalizable checkpoint); public T readItem(); public Externalizable checkpointInfo(); public void close(); } public interface ItemProcessor<T, R> { public R processItem(T item); } public interface ItemWriter<T> { public void open(Externalizable checkpoint); public void writeItems(List<T> items); public Externalizable checkpointInfo(); public void close(); }

13. Handling Exceptions <job id=...> ... <chunk skip-limit=”5” retry-limit=”5”> <skippable-exception-classes> <include class="java.lang.Exception"/> <exclude class="java.io.FileNotFoundException"/> </skippable-exception-classes> • <retryable-exception-classes> ... </retryable-exception-classes> <no-rollback-exception-classes> • ... </no-rollback-exception-classes> </chunk> ... </job>

14. Partitioned Step • A batch step may run as a partitioned step • A partitioned step runs as multiple instances of the same step definition across multiple threads, one partition per thread <step id="step1" > <chunk ...> <partition> <plan partitions=“10" threads="2"/> <reducer .../> </partition> </chunk> </step>

15. Partitioning – Advanced Scenarios • Partition Mapper • Dynamically decide number of partitions (partition plan) • Partition Reducer • Demarcate logical unit of work around partition processing • Partition Collector • Sends interim results from individual partition to step's partition analyzer • Partition Analyzer • Collection point of interim results, single point of control and analysis

16. Flow and Split • Flow defines a set of steps to be executed as a unit <flow id=”flow-1" next=“{flow, step, decision}-id” > <step id=“flow_1_step_1”> </step> <step id=“flow_1_step_2”> </step> </flow> • Split defines a set of flows to be executed in parallel <split …> <flow …./> <!– each flow runs on a separate thread --> <flow …./> </split>

17. Batchlet • Task oriented unit of work • Not item-oriented • Doesn't support resume • Simple Batchlet interface – process(), stop() • In Job XML: <batchlet ref=”{name}”/>

18. Programming Model – Advanced Scenarios • CheckpointAlgorithm • Decider • Listeners – Job, Step, Chunk Listeners … • @BatchPropertyString fname = “/tmp/default.txt” • @BatchContext JobContext jctxt;

19. Batch Runtime Specification • JobOperator interface – for programmatic lifecycle control of jobs • Step level Metrics through the StepExecution object • Batch Artifact loading through CDI • Job XML loading through META-INF/batch-jobs/myJob.xml • Packaging – jar, war, ejb-jar

20. Example: Programmatic Invocation of Jobs In a Servlet/EJB: import javax.batch.runtime.BatchRuntime; ... JobOperator jo = BatchRuntime.getJobOperator(); jo.start("myJob", new Properties()); ...

21. Where to Find Out More • Read the final spec and API docs at http://java.net/projects/jbatch/ • Join public@jbatch.java.net and send questions and comments • RI integrated in GlassFish 4.0 • http://glassfish.java.net

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