How to get MDC logging working for Spring Batch - spring-batch

Question

In Spring Batch it would be great to keep track of the execution thread through logging. However, MDC does not seem to work.
MDC.put("process", "batchJob");
logger.info("{}; status={}", getJobName(), batchStatus.name());
Anyone got MDC working in Spring Batch?

Answer 1

I solved it by adding a JobExecutionListener like that:
public class Slf4jBatchJobListener implements JobExecutionListener {
private static final String DEFAULT_MDC_UUID_TOKEN_KEY = "Slf4jMDCFilter.UUID";
private final Logger logger = LoggerFactory.getLogger(getClass());
public void beforeJob(JobExecution jobExecution) {
String token = UUID.randomUUID().toString().toUpperCase();
MDC.put(DEFAULT_MDC_UUID_TOKEN_KEY, token);
logger.info("Job {} with id {} starting...", jobExecution.getJobInstance().getJobName(), jobExecution.getId());
}
public void afterJob(JobExecution jobExecution) {
logger.info("Job {} with id {} ended.", jobExecution.getJobInstance().getJobName(), jobExecution.getId());
MDC.remove(DEFAULT_MDC_UUID_TOKEN_KEY);
}
}
Because some jobs are multi-threaded, I had to add also a TaskDecorator in order to copy the DMC from the parent thread to the subthread like this:
public class Slf4JTaskDecorator implements TaskDecorator {
#Override
public Runnable decorate(Runnable runnable) {
Map<String, String> contextMap = MDC.getCopyOfContextMap();
return () -> {
try {
MDC.setContextMap(contextMap);
runnable.run();
} finally {
MDC.clear();
}
};
}
}
Set the TaskDecorator to the TaskExecutor:
#Bean
public TaskExecutor taskExecutor(){
SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor("spring_batch");
taskExecutor.setConcurrencyLimit(maxThreads);
taskExecutor.setTaskDecorator(new Slf4JTaskDecorator());
return taskExecutor;
}
And lastly, update the logging pattern in properties:
logging:
pattern:
level: "%5p %X{Slf4jMDCFilter.UUID}"