本文只讲原理,不讲框架。
我们一一来解答:
关于多线程传递,分为两种情况:
比如,上面这个系统,系统入口在A处,A调用B的服务,B里面又起了一个线程B1去访问D的服务,B本身又去访问C服务。
我们就可以这么来跟踪日志:
我们模拟A到B这两个服务来实现一个日志跟踪系统。
为了简单起见,我们使用SpringBoot,它默认使用的日志框架是logback,而且Slf4j提供了一个包装了InheritableThreadLocal的类叫MDC,我们只要把traceId放在MDC中,打印日志的时候统一打印就可以了,不用显式地打印traceId。
我们分成三个模块:
前置过滤器,用拦截器实现也是一样的。
从请求头中获取traceId,如果不存在就生成一个,并放入MDC中。
@Slf4j @WebFilter("/**") @Component public class TraceFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; // 从请求头中获取traceId String traceId = request.getHeader("traceId"); // 不存在就生成一个 if (traceId == null || "".equals(traceId)) { traceId = UUID.randomUUID().toString(); } // 放入MDC中,本文来源于工从号彤哥读源码 MDC.put("traceId", traceId); chain.doFilter(servletRequest, servletResponse); } @Override public void destroy() { } }
改造线程池,提交任务的时候进行包装。
public class TraceThreadPoolExecutor extends ThreadPoolExecutor { public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue); } public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory); } public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler); } public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler); } @Override public void execute(Runnable command) { // 提交者的本地变量 Map<String, String> contextMap = MDC.getCopyOfContextMap(); super.execute(()->{ if (contextMap != null) { // 如果提交者有本地变量,任务执行之前放入当前任务所在的线程的本地变量中 MDC.setContextMap(contextMap); } try { command.run(); } finally { // 任务执行完,清除本地变量,以防对后续任务有影响 MDC.clear(); } }); } }
改造Spring的异步线程池,包装提交的任务。
@Slf4j @Component public class TraceAsyncConfigurer implements AsyncConfigurer { @Override public Executor getAsyncExecutor() { ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); executor.setCorePoolSize(8); executor.setMaxPoolSize(16); executor.setQueueCapacity(100); executor.setThreadNamePrefix("async-pool-"); executor.setTaskDecorator(new MdcTaskDecorator()); executor.setWaitForTasksToCompleteOnShutdown(true); executor.initialize(); return executor; } @Override public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() { return (throwable, method, params) -> log.error("asyc execute error, method={}, params={}", method.getName(), Arrays.toString(params)); } public static class MdcTaskDecorator implements TaskDecorator { @Override public Runnable decorate(Runnable runnable) { Map<String, String> contextMap = MDC.getCopyOfContextMap(); return () -> { if (contextMap != null) { MDC.setContextMap(contextMap); } try { runnable.run(); } finally { MDC.clear(); } }; } } }
封装Http工具类,把traceId加入头中,带到下一个服务。
@Slf4j public class HttpUtils { public static String get(String url) throws URISyntaxException { RestTemplate restTemplate = new RestTemplate(); MultiValueMap<String, String> headers = new HttpHeaders(); headers.add("traceId", MDC.get("traceId")); URI uri = new URI(url); RequestEntity<?> requestEntity = new RequestEntity<>(headers, HttpMethod.GET, uri); ResponseEntity<String> exchange = restTemplate.exchange(requestEntity, String.class); if (exchange.getStatusCode().equals(HttpStatus.OK)) { log.info("send http request success"); } return exchange.getBody(); } }
A服务通过Http调用B服务。
@Slf4j @RestController public class AController { @RequestMapping("a") public String a(String name) { log.info("Hello, " + name); try { // A中调用B return HttpUtils.get("http://localhost:8002/b"); } catch (Exception e) { log.error("call b error", e); } return "fail"; } }
A服务的日志输出格式:
中间加了 [%X{traceId}]
一串表示输出traceId。
# 本文来源于工从号彤哥读源码 logging: pattern: console: '%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(%5p) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr([%X{traceId}]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n%wEx'
B服务内部有两种跨线程调用:
BController.java
@Slf4j @RestController public class BController { @Autowired private BService bService; @RequestMapping("b") public String b() { log.info("Hello, b receive request from a"); bService.sendMsgBySpring(); bService.sendMsgByThreadPool(); return "ok"; } }
BService.java
@Slf4j @Service public class BService { public static final TraceThreadPoolExecutor threadPool = new TraceThreadPoolExecutor(5, 5, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<>(100)); @Async public void sendMsgBySpring() { log.info("send msg by spring success"); } public void sendMsgByThreadPool() { threadPool.execute(()->log.info("send msg by thread pool success")); } }
B服务的日志输出格式:
中间加了 [%X{traceId}]
一串表示输出traceId。
logging: pattern: console: '%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(%5p) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr([%X{traceId}]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n%wEx'
打开浏览器,输入 http://localhost:8001/a?name=andy
。
A服务输出日志:
2019-12-26 21:36:29.132 INFO 5132 --- [nio-8001-exec-2] [8a59cb96-bbc8-42a9-aa62-df7a52875447] com.alan.trace.a.AController : Hello, andy 2019-12-26 21:36:35.380 INFO 5132 --- [nio-8001-exec-2] [8a59cb96-bbc8-42a9-aa62-df7a52875447] com.alan.trace.common.HttpUtils : send http request success
B服务输出日志:
2019-12-26 21:36:29.244 INFO 2368 --- [nio-8002-exec-1] [8a59cb96-bbc8-42a9-aa62-df7a52875447] com.alan.trace.b.BController : Hello, b receive request from a 2019-12-26 21:36:29.247 INFO 2368 --- [nio-8002-exec-1] [8a59cb96-bbc8-42a9-aa62-df7a52875447] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 2019-12-26 21:36:35.279 INFO 2368 --- [ async-pool-1] [8a59cb96-bbc8-42a9-aa62-df7a52875447] com.alan.trace.b.BService : send msg by spring success 2019-12-26 21:36:35.283 INFO 2368 --- [pool-1-thread-1] [8a59cb96-bbc8-42a9-aa62-df7a52875447] com.alan.trace.b.BService : send msg by thread pool success
可以看到,A服务成功生成了traceId,并且传递给了B服务,且B服务线程间可以保证同一个请求的traceId是可以传递的。