스프링 배치 도메인 이해 -ExecutionContext

ExecutionContext

1) 기본 개념

• 프레임워크에서 유지 및 관리하는 키/값으로 된 컬렉션. (Map)
• StepExecution 또는 JobExecution 객체의 상태를 저장하는 공유 객체
• DB에 직렬화한 값으로 저장됨. {"key":"value"}
• 공유 범위
  • Step 범위 - 각 Step의 StepExecution에 저장되며 Step간 서로 공유 안됨.
  • Job 범위 : 각 Job의 JobExecution에 저장되며 Job간 서로 공유 안됨. 해당 Job의 Step간 서로 공유됨.
    • Job -> Step1, Step2, Step3, Step4,….
      Step1, Step2, Step3, Step4에서 Job 참조 가능.
      스텝간 데이터 공유가 필요하다면 job의 ExecutionContext 활용
• Job 재시작시 이미 처리한 Row 데이터는 건너뛰고 이후로 수행하도록 할 때 상태 정보를 활용한다.

 

2) 구조

BATCH_JOB_EXECUTION_CONTEXT

job_execution_id	short_context	serialized_context
1	{ “inputCount” : “150” , “date” : “20210101”}

BATCH_STEP_EXECUTION_CONTEXT

step_execution_id	short_context	serialized_context
1	{"batch.taskletType":"io.batch.springbatch.job.HelloJobConfiguration$1", "name":"leaven", "batch.stepType":"org.springframework.batch.core.step.tasklet.TaskletStep"}

 

실습

실습 1) Job, Step간 공유 범위 확인

@RequiredArgsConstructor
@Configuration
public class ExecutionContextConfiguration {
    private final JobBuilderFactory jobBuilderFactory;
    private final StepBuilderFactory stepBuilderFactory;
    private final ExecutionContextTasklet1 executionContextTasklet1;
    private final ExecutionContextTasklet2 executionContextTasklet2;
    private final ExecutionContextTasklet3 executionContextTasklet3;

    @Bean
    public Job BatchJob() {
        return this.jobBuilderFactory.get("Job")
                .start(step1())
                .next(step2())
                .next(step3())
                .build();
    }

    public Step step1() {
        return stepBuilderFactory.get("step1")
                .tasklet(executionContextTasklet1)
                .build();
    }

    public Step step2() {
        return stepBuilderFactory.get("step2")
                .tasklet(executionContextTasklet2)
                .build();
    }

    public Step step3() {
        return stepBuilderFactory.get("step3")
                .tasklet(executionContextTasklet3)
                .build();
    }
}

Step1, Step2, Step3이 순차적으로 실행된다.

@Component
public class ExecutionContextTasklet1 implements Tasklet {

    @Override
    public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
        System.out.println("ExecutionContextTasklet1 has executed");
        
        ExecutionContext jobExecutionContext = contribution.getStepExecution().getJobExecution().getExecutionContext();
        ExecutionContext stepExecutionContext = contribution.getStepExecution().getExecutionContext();

        String jobName = chunkContext.getStepContext().getStepExecution().getJobExecution().getJobInstance().getJobName();
        String stepName = chunkContext.getStepContext().getStepExecution().getStepName();

        if (jobExecutionContext.get("jobName") == null) {
            jobExecutionContext.put("jobName", jobName);
        }

        if (stepExecutionContext.get("stepName") == null) {
            stepExecutionContext.put("stepName", stepName);
        }

        System.out.println("jobName : " + jobExecutionContext.get("jobName"));
        System.out.println("stepName : " + stepExecutionContext.get("stepName"));

        return RepeatStatus.FINISHED;
    }
}

Step1 : "jobName"이 없으면 jobExecutionContext에, "stepName"이 없으면 stepExecutionContext에 넣어준다.

- 출력
ExecutionContextTasklet1 has executed
jobName : Job
stepName : step1

@Component
public class ExecutionContextTasklet2 implements Tasklet {

    @Override
    public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
        System.out.println("ExecutionContextTasklet2 has executed");
        ExecutionContext jobExecutionContext = contribution.getStepExecution().getJobExecution().getExecutionContext();
        ExecutionContext stepExecutionContext = contribution.getStepExecution().getExecutionContext();
        System.out.println("jobName : " + jobExecutionContext.get("jobName"));
        System.out.println("stepName : " + stepExecutionContext.get("stepName"));

        String stepName = chunkContext.getStepContext().getStepExecution().getStepName();

        if (stepExecutionContext.get("stepName") == null) {
            stepExecutionContext.put("stepName", stepName);
        }

        System.out.println("stepName : " + stepExecutionContext.get("stepName"));

        return RepeatStatus.FINISHED;
    }
}

 

Step2 : jobName, stepName을 출력한다. StepExecution은 Step간 공유되지 않으므로 첫 번째 stepName 출력에서는 null이 나온다.

- 출력
ExecutionContextTasklet2 has executed
jobName : Job
stepName : null
stepName : step2

@Component
public class ExecutionContextTasklet3 implements Tasklet {

    @Override
    public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {

        System.out.println("ExecutionContextTasklet3 has executed");

        Object name = chunkContext.getStepContext().getStepExecution().getJobExecution().getExecutionContext().get("name");

        if (name == null) {
            chunkContext.getStepContext().getStepExecution().getJobExecution().getExecutionContext().put("name", "user1");
            // 아래에서 실패후 재시작했을 때 name 확인.
            System.out.println("ExecutionContextTasklet3 fail!");
            throw new RuntimeException("step has failed");
        }

        return RepeatStatus.FINISHED;
    }
}

Step3 : 의도적으로 예외를 날린다.

- 출력
ExecutionContextTasklet3 has executed
ExecutionContextTasklet3 fail!

 

실습 2) 실습 1 재시작

Step1, Step2는 실습 1에서 성공하였기 때문에 Skip하고 Step3을 실행하게 된다.

실습 2에서는 실습 1에서 저장된 "name"이 있어 null이 아니기 때문에 에러가 발생하지 않는다.

- 출력
ExecutionContextTasklet3 has executed