在 Spring 批处理小任务中使用多个数据源

Question

I am new to spring batch, and I'm encountering an issue when using multiple data source in my batch.

Let me explain.

I am using 2 databases in my server with Spring Boot.

So far everything worked fine with my implementation of RoutingDataSource.

@Component("dataSource")
public class RoutingDataSource extends AbstractRoutingDataSource {

  @Autowired
  @Qualifier("datasourceA")
  DataSource datasourceA;

  @Autowired
  @Qualifier("datasourceB")
  DataSource datasourceB;

  @PostConstruct
  public void init() {
    setDefaultTargetDataSource(datasourceA);
    final Map<Object, Object> map = new HashMap<>();
    map.put(Database.A, datasourceA);
    map.put(Database.B, datasourceB);
    setTargetDataSources(map);
  }

  
  @Override
  protected Object determineCurrentLookupKey() {
    return DatabaseContextHolder.getDatabase();
  }
}

The implementation require a DatabaseContextHolder, here it is:

public class DatabaseContextHolder {
    private static final ThreadLocal<Database> contextHolder = new ThreadLocal<>();

    public static void setDatabase(final Database dbConnection) {
        contextHolder.set(dbConnection);
    }

    public static Database getDatabase() {
        return contextHolder.get();
    }
}

When I received a request on my server, I have a basic interceptor that sets the current database based on some input I have in the request. with the method DatabaseContextHolder.setDatabase(db); Everything works fine with my actual controllers.

It gets more complicated when I try to run a job with one tasklet.

One of my controller start an async task like this.

@GetMapping("/batch")
public void startBatch() {
  return jobLauncher.run("myJob", new JobParameters());
}

@EnableBatchProcessing
@Configuration
public class MyBatch extends DefaultBatchConfigurer {


  @Autowired private JobBuilderFactory jobs;

  @Autowired private StepBuilderFactory steps;

  @Autowired private MyTasklet tasklet;

  @Bean
  public Job job(Step step) {
    return jobs.get("myJob").start(step).build();
  }

  @Bean
  protected Step registeredDeliveryTask() {
    return steps.get("myTask").tasklet(tasklet).build();
  }

  /** Overring the joblauncher get method to make it asynchornous */
  @Override
  public JobLauncher getJobLauncher() {
    try {
      SimpleJobLauncher jobLauncher = new SimpleJobLauncher();
      jobLauncher.setJobRepository(super.getJobRepository());
      jobLauncher.setTaskExecutor(new SimpleAsyncTaskExecutor());
      jobLauncher.afterPropertiesSet();
      return jobLauncher;
    } catch (Exception e) {
      throw new BatchConfigurationException(e);
    }
  }
}

And my Tasklet:

@Component
public class MyTasklet implements Tasklet {

  @Autowired
  private UserRepository repository;

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

  //Do stuff with the repository.

  }

But the RoutingDataSource doesn't work, even if I set my Context before starting the job. For example if I set my database to B, the repo will work on database A. It is always the default datasource that is selected. (because of this line setDefaultTargetDataSource(datasourceA); )

I tried to set the database, by passing the value in the parameters, inside the tasklet, but still got the same issue.

@GetMapping("/batch")
public void startBatch() {
  Map<String, JobParameter> parameters = new HashMap<>();
  parameters.put("database", new JobParameter(DatabaseContextHolder.getCircaDatabase().toString()));
  return jobLauncher.run("myJob", new JobParameters(parameters));
}

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

    String database =
        chunkContext.getStepContext().getStepExecution().getJobParameters().getString("database");
    DatabaseContextHolder.setDatabase(Database.valueOf(database));
  //Do stuff with the repository.

  }

I feel like the problem is because the database was set in a different thread, because my job is asynchronous. So it cannot fetch the database set before launching the job. But I couldn't find any solution so far.

Regards

Answer 1

Your routing datasource is being used for Spring Batch's meta-data, which means the job repository will interact with a different database depending on the thread processing the request. This is not needed for batch jobs. You need to configure Spring Batch to work with a fixed data source.