Spring Day | Behind the Scenes at Spring Batch | Dave Syer
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The document provides an overview of Spring Batch, detailing its quick start, administration, state management, retry and skip mechanisms, and transaction handling. It emphasizes item-oriented processing, job configuration, thread isolation, and quality of service in the context of batch processing. Additionally, it highlights the framework's failure management strategies and the importance of maintaining state for job execution and recovery.
Spring Day | Behind the Scenes at Spring Batch | Dave Syer
- 1. Inside Spring Batch Dave Syer, VMware, JAX London 2011 Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
- 2. Overview • Very quick start with Spring Batch • Spring Batch Admin • State management – thread isolation • Retry and skip • Restart and transactions Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 2
- 3. Processing the Same File Twice… Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 3
- 4. Spring Batch Application Business logic Batch Core Quality of service, Batch Infrastructure auditability, management information Re-usable low level stuff: flat files, XML files, database keys Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 4
- 5. Spring Batch Admin Application Batch Core Runtime services (JSON and Java) plus optional UI Batch Infrastructure Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 5
- 6. Simple Sequential Sample <job id="job"> <step id="businessStep"> <tasklet> <chunk reader="itemGenerator" writer="itemWriter" commit-interval="1"/> </tasklet> <next on="FAILED" to="recoveryStep"/> <end on="*"/> </step> <step id="businessStep"> <tasklet ref="reportFailure" /> </step> </job> Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 6
- 7. Item-Oriented Processing • Input-output can be grouped together = Item-Oriented Processing Step ItemReader ItemWriter execute() read() item repeat, retry, write(items) etc. ExitStatus Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 7
- 8. Job Configuration and Execution The EndOfDay Job Job schedule.date = 2007/05/05 JobParameters * The EndOfDay Job JobInstance for 2007/05/05 * The first attempt at JobExecution EndOfDay Job for 2007/05/05 Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 8
- 9. State Management • Isolation – thread safety • Retry and skip • Restart Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 9
- 10. Thread Isolation: StepScope File writer needs to be step scoped so it can flush and close the output stream <bean class="org.sfw...FlatFileItemWriter" scope=“step”> <property name=“resource"> <value> /data/#{jobName}-{#stepName}.csv </value> </property> </bean> Because it is step scoped the writer has access to the StepContext and can replace these patterns with runtime values Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 10
- 11. Step Scope Responsibilities • Create beans for the duration of a step • Respect Spring bean lifecycle metadata (e.g. InitializingBean at start of step, DisposableBean at end of step) • Recognise StepScopeAware components and inject the StepContext • Allows stateful components in a multithreaded environment • Well-known internal services recognised automatically Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 11
- 12. Quality of Service • Stuff happens: – Item fails – Job fails • Failures can be – Transient – try again and see if you succeed – Skippable – ignore it and maybe come back to it later – Fatal – need manual intervention • Mark a job execution as FAILED • When it restarts, pick up where you left off • All framework concerns: not business logic Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 12
- 13. Quality of Service Sample <step id="step1"> <tasklet> <chunk reader="itemGenerator" writer="itemWriter" commit-interval="1" retry-limit="3" skip-limit="10"> ... </chunk> </tasklet> </step> Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 13
- 14. Retry and the Transaction REPEAT(while more input) { chunk = ACCUMULATE(size=500) { Chunk input; Provider } RETRY { TX { for (item : chunk) { process; } write; Chunk } Processor } } Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 14
- 15. Retry and Skip: Failed Processor RETRY(up to n times) { TX { Skip is just for (item : chunk) { process; } an exhausted write; retry } } RECOVER { TX { for (item : successful) { process; } write; skip(item); } } } Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 15
- 16. Flushing: ItemWriter public class RewardWriter implements ItemWriter<Reward> { public void write(List<Reward> rewards) { // do stuff to output Reward records // and flush changes here… } } Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 16
- 17. Retry and Skip: Failed Write RETRY(up to n times) { TX { for (item : chunk) { process; } write; Scanning for } failed item } RECOVER { for (item : chunk) { TX { process; write; } CATCH { skip(item); } } } Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 17
- 18. Restart and Partial Failure • Store state to enable restart • What happens to the business data on error? • What happens to the restart data? • Goal: they all need to rollback together Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 18
- 19. Partial Failure: Piggyback the Business Transaction JOB { STEP { REPEAT(while more input) { TX { Inside REPEAT(size=500) { business input; transaction output; } FLUSH and UPDATE; Database } } Persist } context data for next } execution Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 19
- 20. ItemStream Step ItemStream JobRepository execute() open(executionContext) Called before commit repeat, update(executionContext) retry, etc. save(executionContext) close() ExitStatus Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 20
- 21. Overview • Very quick start with Spring Batch • Spring Batch Admin • State management – thread isolation • Retry and skip • Restart and transactions Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 21
- 22. Q&A Copyright 2007 SpringSource. Copying, publishing or distributing without express written permission is prohibited.