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This article mainly shows you "how to print a unique traceId in the Springboot+MDC+traceId log", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn how to print a unique traceId in the Springboot+MDC+traceId log "this article.

Look at a picture first:

Some students asked: how is the traceId similar to uuid in the log implemented? this article introduces how to use MDC to print traceId in log files under the springboot project.

1. Why do you need this traceId?

When we locate the problem, we need to find the corresponding location in the log. When the request of an API uses a unique traceId, then we only need to know the traceId and use the grep 'traceId' xxx.log statement to locate the target log accurately. Here the article describes how to set the traceId and then how to return the traceId on the interface.

# API returns: {"code": "0", "dealStatus": "1", "TRACE_ID": "a10e6e8d-9953-4de9-b145-32eee6aa5562"} # query log grep 'a10e6e8d-9953-4de9-b145-32eee6aa5562' xxxx.log2. Set up traceId through MDC

The project that the author encounters at present, can have three situations to set up traceId. First a brief introduction to MDC

# MDC defines Mapped Diagnostic Context, that is, mapping diagnostic environment. MDC is a function provided by log4j and logback to facilitate logging under multithreaded conditions. MDC can be thought of as a hash table bound to the current thread to which you can add key-value pairs. # how to use MDC to set values to MDC: MDC.put (key, value); value from MDC: MDC.get (key); print the contents of MDC to the log:% X {key} 2.1 use filter filter to set traceId

Create a new filter, implement Filter, override the init,doFilter,destroy method, set the traceId to be placed in doFilter, and call the MDC.clear () method in destroy.

Slf4j@WebFilter (filterName = "traceIdFilter", urlPatterns = "/ *") public class traceIdFilter implements Filter {/ * Log tracking ID * / private static final String TRACE_ID = "TRACE_ID" @ Override public void init (FilterConfig filterConfig) throws ServletException {} @ Override public void doFilter (ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {MDC.put (TRACE_ID, UUID.randomUUID (). ToString ()); filterChain.doFilter (request, servletResponse);} @ Override public void destroy () {MDC.clear ();} 2.2 projects using JWT token filters

Springboot projects often use spring security+jwt to restrict permissions. In this case, we set traceId by creating a new filter filter, so the log verifying token will not have traceId, so we need to put the code in jwtFilter, as shown below:

/ * token filter verifies token validity * * @ author china * / @ Componentpublic class JwtAuthenticationTokenFilter extends OncePerRequestFilter {@ Autowired private TokenService tokenService; / * Log tracking ID * / private static final String TRACE_ID = "TRACE_ID"; @ Override protected void doFilterInternal (HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws ServletException, IOException {MDC.put (TRACE_ID, UUID.randomUUID (). ToString ()) LoginUser loginUser = tokenService.getLoginUser (request); if (StringUtils.isNotNull (loginUser) & & StringUtils.isNull (SecurityUtils.getAuthentication () {tokenService.verifyToken (loginUser); UsernamePasswordAuthenticationToken authenticationToken = new UsernamePasswordAuthenticationToken (loginUser, null, loginUser.getAuthorities ()); authenticationToken.setDetails (new WebAuthenticationDetailsSource (). BuildDetails (request)); SecurityContextHolder.getContext (). SetAuthentication (authenticationToken) } chain.doFilter (request, response);} @ Override public void destroy () {MDC.clear ();}} 2.3 use Interceptor interceptor to set traceId

Define an interceptor, override the preHandle method, and set the traceId through MDC in the method

/ * MDC sets traceId interceptor * * @ author china * / @ Componentpublic abstract class TraceIdInterceptor extends HandlerInterceptorAdapter {private static final String UNIQUE_ID = "TRACE_ID"; @ Override public boolean preHandle (HttpServletRequest request, HttpServletResponse response, Object handler) {MDC.put (UNIQUE_ID, UUID.randomUUID (). ToString ()); return true } @ Override public void afterCompletion (HttpServletRequest request, HttpServletResponse response, Object handler, @ Nullable Exception ex) throws Exception {MDC.clear ();}} configure traceId in 3.logback.xml

Compared to the previous one, we just added [% X {TRACE_ID}], [% X {* *}] is a template, and the middle attribute name is entered using MDC put.

Before # after adding traceId 4. Supplement the traceId brought into the context by asynchronous methods

The asynchronous method starts a new thread. If the asynchronous method and the main thread share the same traceId, we first create a new task adapter MdcTaskDecorator, as shown in the figure:

Public class MdcTaskDecorator implements TaskDecorator / * causes the asynchronous thread pool to obtain the context of the main thread * @ param runnable * @ return * / @ Override public Runnable decorate (Runnable runnable) {Map map = MDC.getCopyOfContextMap (); return ()-> {try {MDC.setContextMap (map); runnable.run () } finally {MDC.clear ();}};}}

Then, add the setting of executor.setTaskDecorator (new MdcTaskDecorator ()) to the thread pool configuration

/ * @ author china * * / @ EnableAsync@Configurationpublic class ThreadPoolConfig {private int corePoolSize = 50; private int maxPoolSize = 200; private int queueCapacity = 1000; private int keepAliveSeconds = 300; @ Bean (name = "threadPoolTaskExecutor") public ThreadPoolTaskExecutor threadPoolTaskExecutor () {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor (); executor.setMaxPoolSize (maxPoolSize); executor.setCorePoolSize (corePoolSize); executor.setQueueCapacity (queueCapacity) Executor.setKeepAliveSeconds (keepAliveSeconds); executor.setTaskDecorator (new MdcTaskDecorator ()); / / Thread pool policy executor.setRejectedExecutionHandler (new ThreadPoolExecutor.CallerRunsPolicy ()) for rejecting tasks (wireless paths are available); return executor;}}

Finally, use @ Async to turn on the asynchronous method on the business code

Async ("threadPoolTaskExecutor") void testSyncMethod (); 5. In the API playback, add traceId return

In the author's project, the interface return is wrapped by a custom class called AjaxResult, so you only need to add traceId return to the constructor of this class, which is relatively simple.

/ * Log trace ID * / private static final String TRACE_ID = "TRACE_ID"; / * initialize a newly created AjaxResult object to represent an empty message. * / public AjaxResult () {super.put (TRACE_ID, MDC.get (TRACE_ID));} / * initialize a newly created AjaxResult object * * @ param code status code * @ param msg returns content * / public AjaxResult (int code, String msg) {super.put (CODE_TAG, code) Super.put (MSG_TAG, msg); super.put (TRACE_ID, MDC.get (TRACE_ID)) } / * initialize a newly created AjaxResult object * * @ param code status code * @ param msg returns the content * @ param data data object * / public AjaxResult (int code, String msg, Object data) {super.put (CODE_TAG, code); super.put (MSG_TAG, msg) Super.put (TRACE_ID, MDC.get (TRACE_ID)); if (StringUtils.isNotNull (data)) {super.put (DATA_TAG, data);}} these are all the contents of the article "how to print a unique traceId in the Springboot+MDC+traceId log". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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