three key concepts for understanding jsr-352: batch programming for the java platform

© 2013 IBM Corporation

Timothy C. Fanelli - Senior IT Specialist

23 September 2013

Three Key Concepts for Understanding JSR-352: Batch Applications for the Java Platform


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About me

§ Timothy C. Fanelli

§ Senior IT Specialist, IBM - Mainframe Workload Modernization

§ Instructor of Software Engineering - Clarkson University, Potsdam NY

§ [email protected]

§ [email protected], [email protected]

§ Visit the IBM booth #5112 and meet other IBM developers at JavaOne 2013

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mailto:[email protected]







Agenda

§ Background

§ Three Key Concepts– Implementation– Orchestration– Execution

§ An Example JSR 352 Application

§ Advanced Topics– Splits and Flows– Partitioning– Java EE

§ Conclusion and Thoughts on What’s Next...

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Background


Batch Processing

§ One of the oldest processing paradigms

§ Historically associated with mainframe computing

§ Still incredibly relevant today, with fresh challenges in an OLTP driven world

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Java for Batch Processing?

§ Mainframe developers have shied away from Java– Performance concerns over native languages– Integration concerns for legacy data– Disparate developer skill set between System Z and Java

§ Java and JavaEE have dominated the Online Transaction Processing world

§ Time to bridge the two worlds together– IBM Java for zOS, IBM WebSphere, and Spring Batch paved new paths– Just-in-Time Compilation, Garbage Collection optimizations proved it out– Adoption is wide-spread!

§ Only remaining challenge was the lack of a standard– The need for JSR-352 was obvious

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JSR 352: Batch Applications for the Java Platform

§ Expert working group formed 29 November 2011– IBM*, VMWare, RedHat, Oracle, Credit Suisse, Independent participants– Broad range of talent with deep batch experience

§ Final Release 24 May 2013

§ Included in Java EE 7!

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Three Key Concepts...


Three Key Concepts ...

§ JSR 352 defines– Implementation: A programming model for

implementing the artifacts – Orchestration: A Job Specification Language,

which orchestrates the execution of a batch artifacts within a job.

– Execution: A runtime environment for executing batch application, according to a defined lifecycle.

§ Note: “key” concepts, not “new” concepts! – Roles and abstractions should be familiar to

SOA and JavaEE developers

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Implement

Execute

Orchestrate


Anatomy of JSR352

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Implement

Execute

Orchestrate

§ Those concepts define the anatomy of JSR 352: Batch Applications for the Java Platform...

Job Repository

JobOperator Job Step

Batchlet

Chunk

Reader

Processor

Writer

ChunkChunk

ChunkListeners

ListenersContexts

ListenersPartitioning


Implementation: The programming model

§ Chunk and Batchlet provide models for implementing a step.

§ Contexts provide Job- and Step- level runtime information, and provide interim data persistence.

§ Listeners provide callback hooks to respond to lifecycle events on batch artifacts.

§ Partitioning provides a mechanism imposing parallel processing on jobs and steps

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Batchlet

Chunk

Reader

Processor

Writer

ChunkChunkChunkListeners

ListenersContexts



Implementation: The programming modelChunk vs Batchlet

§ Both are implementations of a step within a batch job

§ The chunk model– Encapsulates a very common pattern: ETL– Single “reader”, “processor” and “writer”– Reader/Processor combination is invoked until

an entire “chunk” of data is processed– Output “chunk” is written atomically

§ Batchlet provides a “roll your own” step type– Invoked and runs to completion, producing a

return code upon exit.

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Batchlet

Chunk

Reader

Processor

Writer

ChunkChunkChunkListeners

ListenersContexts



Orchestration: The Job Specification Language (JSL)

§ The JSL defines a batch job as an XML document

§ Describes a step as an assemblage of batch artifacts

§ Provides for the description of steps, step groupings, and execution sequencing

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Job Step


Execution: The JobOperator and Repository

§ JobOperator is the runtime interface for job management, including start, stop, restart and job repository related commands

§ The Job Repository holds information about completed and executing jobs

§ To start a batch job, get a JobOperator instance use it to start a job described (described by JSL).

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Job Repository

JobOperator


Execution: JobInstance, JobExecution, and StepExecution

§ The state of a job is broken down into various parts, and persisted in the repository

– Submitting a job creates a JobInstance, a logical representation of a particular “run” of a job.

– A JobExecution is a single attempt to run a JobInstance. A restart attempt creates another JobExecution

– Similarly, a StepExecution is a single attempt to run a step within a job. It is created when a step starts execution.

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Job RepositoryJobOperator

JobInstance

JobExecution

StepExecution

Job Step

*

*

* *


An Example JSR 352 Application


The Application

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‣ A typical “batch hello world”:– Reads strings from an input file– Performs some validation or transforms– Writes validated or transformed string to an output file

‣ Key capabilities– If something goes wrong, we don’t want to discard all the

prior work; and we want to pick up where we left off– We want control over the transaction scoping so prevent

lock contention in high volume periods– We want flexibility to “plug and play” where our records

come from– For unit testing, development testing, and QA testing -

records may come from a variety of sources


The Design

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‣ Let’s implement a string-transform in an extract-transform-load pattern

‣ We’ll use JSR352’s Chunk programming model– Encapsulates the ETL pattern components as Reader, Processor, and Writer interfaces– Loosely coupled artifacts will be orchestrated into a single-step job later– “Free” checkpoint/restart capability– Transaction scoping imposed externally in the job descriptor

‣ Job will be executed as a Java SE command line batch application


The Code

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Implement

‣ An ItemReader encapsulates the data access and deserialization of a record.

‣ No restriction on data access paradigm: use DAO patterns, JDBC, JPA, Hibernate, Spring Data, etc!

‣ Checkpoint/Restart data provided as Serializable argument to “open” and from “checkpointInfo” methods.


The Code

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Implement

§ An ItemWriter is the output counterpart to ItemReader

§ Primary difference is that writeItems accepts a “chunk” of output objects (as a list) to serialize.

§ Again, no restriction on data access paradigm!


The Code

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Implement

§ An ItemProcessor encapsulates the business logic applied to each record

§ “main” here demonstrates the invocation of a batch job, using the JobOperator

§ Would typically not be in the processor implementation


The Batch Descriptor and Job Specification

§ batch.xml defines and names the batch artifacts in this application archive

§ sample.xml is an example Job Specification Language document for SampleBatchApp

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Orchestrate


The Execution

§ Package the application as a standard JAR or WAR for deployment in JavaSE or EE environments

– batch.xml goes in META-INF or WEB-INF/classes/META-INF

– JSL may go in META-INF/batch-jobs, or submitted from an external source (up to the provider!)

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Execute


The Execution

§ See it live?

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Execute


Advanced Topics


Job Management - Restart, Stop, Abandon

§ Had something gone wrong, what then?– The “main” program shown was too simple... only

“started” the job

§ JobOperator exposes APIs for a variety of job management tasks: start, stop, abandon, restart

– Would have had to take advantage of these for advanced job management capabilities.

§ The door is left open for more advanced batch job management systems to be built!

– Integration into existing enterprise schedulers?– New Java EE batch scheduling standard?– Plenty of options, but currently left to the provider

to implement

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Execute


Java EE Integration

§ JSR-352: Java Batch is included in Java EE 7

§ Provides EE clustering, security, resource management, etc to Java Batch applications

§ Performance benefits to dispatching into long-running, reusable container

– JIT compilation through the first couple runs – Eliminates overhead of starting / stopping JVM

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Execute


Parallel Job Processing

§ Splits and Flows provide a mechanism for executing job steps concurrently at the orchestration layer

§ A flow is a sequence of one or more steps which execute sequentially, but as a single unit.

§ A Split is a collection of flows that may execute concurrently

– A split may only contain “flows”; a step is not implicitly a flow

§ This is done entirely in the JSL descriptor– Imposed on the batch application with no code

changes!

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Orchestrate



§ Step-level parallelism can be achieved programmatically using step partitioning

§ A partitioned step runs as multiple instances with distinct property sets

§ PartitionMapper defines the number of partitions, and property values for each partition

– Can be a fixed set of partitions in JSL– Can be dynamic using a PartitionMapper implementation

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Implement



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Wrap up...


Batch Processing

§ The oldest “new thing” in Java

§ JSR 352 applies the modern thinking and abstraction of Java EE and SOA and applies it to sequential batch processing

§ The standardized programming model provides application developers vendor portability

§ Inclusion in Java EE 7 ensures wide spread availability

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Questions?

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three key concepts for understanding jsr-352: batch programming for the java platform

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