Skywalking跨线程追踪.md

Skywalking 官方不支持 Log4j 的异步线程打印 traceId，官方给出的答复是：用户通过线程间 traceid 传递解决。

Issue 地址：apache/skywalking#2938

同时官方也给出了跨线程追踪的解决方案，详见：跨线程追踪。具体有以下几种方法。

方法1：@TraceCrossThread

@TraceCrossThread
public static class MyCallable<String> implements Callable<String> {
    @Override
    public String call() throws Exception {
        return null;
    }
}
...
ExecutorService executorService = Executors.newFixedThreadPool(1);
executorService.submit(new MyCallable());

方法2：CallableWrapper/RunnableWrapper

ExecutorService executorService = Executors.newFixedThreadPool(1);
executorService.submit(CallableWrapper.of(new Callable<String>() {
    @Override
    public String call() throws Exception {
        return null;
    }
}));

或者

ExecutorService executorService = Executors.newFixedThreadPool(1);
executorService.execute(RunnableWrapper.of(new Runnable() {
    @Override
    public void run() {
        //your code
    }
}));

方法3：SupplierWrapper

@TraceCrossThread
public class MySupplier<String> implements Supplier<String> {
    @Override
    public String get() {
        return null;
    }
}
 
CompletableFuture.supplyAsync(new MySupplier<String>());

或者

CompletableFuture.supplyAsync(SupplierWrapper.of(() -> {
            return "SupplierWrapper";
    })).thenAccept(System.out::println);

方法4：@Async

社区对 Spring 的 @Async 注解进行了增强，支持子线程的 traceId 打印。代码实现详见：apache/skywalking#2902

在应用启动类上添加 @EnableAsync 注解：

@EnableAsync
@SpringBootApplication
public class WebApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(WebApplication.class, args);
    }
 
}

接口定义如下：

@Slf4j
@RestController
public class ExampleController {
 
    @Autowired
    private ExampleService exampleService;
 
    @GetMapping("/traceid")
    public void traceid() {
        log.info("main thread");
        exampleService.asyncMethod();
    }
 
}

使用 @Async 注解：

@Slf4j
@Service
public class ExampleService {
 
    @Async
    public void asyncMethod() {
        log.info("async method call.");
    }
 
}

日志打印如下：