How to implement logging in CompletableFuture in Java

1. First use aop to add requestId to all request entries.

@Aspect
@Component
public class LoggingAspect {

    /**
     * AOP注解的Controller类方法必须为 public 或 protect ，千万不能用private！！！！！！！！否则会@Autowired注入的service会报空指针异常。
     * 私有方法和字段不属于Spring上下文中的bean属性。
     */
    @Around("@annotation(org.springframework.web.bind.annotation.GetMapping) || " +
            "@annotation(org.springframework.web.bind.annotation.PostMapping) || " +
            "@annotation(org.springframework.web.bind.annotation.PutMapping) || " +
            "@annotation(org.springframework.web.bind.annotation.DeleteMapping)")
    public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {
        // 在logback-spring.xml里对应%X{requestId}
        MDC.put("requestId", UUID.randomUUID().toString().substring(0, 13));  // Add request ID to MDC
        try {
            return joinPoint.proceed(); // Execute method
        } finally {
            MDC.remove("requestId");  // Remove request ID from MDC
        }
    }
}

2. Define logback-spring.xml and introduce requestId for link recording. The key code is %X{requestId}

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!-- 控制台日志格式 -->
    <property name="CONSOLE_LOG_PATTERN" value="${CONSOLE_LOG_PATTERN:-%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %X{requestId} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}"/>
    <!-- 控制台日志格式 依赖的渲染类 -->
    <conversionRule conversionWord="clr" converterClass="org.springframework.boot.logging.logback.ColorConverter" />
    <conversionRule conversionWord="wex" converterClass="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter" />
    <conversionRule conversionWord="wEx" converterClass="org.springframework.boot.logging.logback.ExtendedWhitespaceThrowableProxyConverter" />
    <!-- 输出到控制台 -->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
                <level>debug</level>
            </filter>
            <!-- 配置日志输出格式 -->
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
            <!-- 使用的字符集 -->
            <charset>UTF-8</charset>
        </encoder>
    </appender>


    <!-- 定义输出的路径，获取application.yml的source的值 -->
    <springProperty scope="context" name="LOG_FILE_PATH" source="logging.file-location" default="/var/log/myapp"/>
    <!-- 2.输出到文件 -->
    <!-- 2.1 level为 DEBUG 日志，时间滚动输出  -->
    <appender name="DEBUG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_FILE_PATH}/debug.log</file> <!-- 文件路径 -->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %X{requestId} [%thread] %-5level %logger{50} - %msg%n</pattern><!-- 日志文档输出格式 -->
            <charset>UTF-8</charset>
        </encoder>
        <!-- 日志记录器的滚动策略，按日期，按大小记录 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- 每天新开一个文件 -->
            <fileNamePattern>${LOG_FILE_PATH}/debug-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <!-- 每天100m新开一个文件 -->
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>100MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <!-- 日志文档保留天数 -->
            <maxHistory>15</maxHistory>
            <!-- 用来指定日志文件的上限大小，例如设置为1GB的话，那么到了这个值，就会删除旧的日志。 -->
            <totalSizeCap>1GB</totalSizeCap>
        </rollingPolicy>
        <!-- 此日志文档只记录debug级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>debug</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.2 level为 INFO 日志，时间滚动输出  -->
    <appender name="INFO_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_FILE_PATH}/info.log</file>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %X{requestId} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset>
        </encoder>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${LOG_FILE_PATH}/info-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>100MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录info级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>info</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.3 level为 WARN 日志，时间滚动输出  -->
    <appender name="WARN_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_FILE_PATH}/warn.log</file>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %X{requestId} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset> <!-- 此处设置字符集 -->
        </encoder>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${LOG_FILE_PATH}/warn-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>100MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录warn级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>warn</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.4 level为 ERROR 日志，时间滚动输出  -->
    <appender name="ERROR_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_FILE_PATH}/error.log</file>
        <!--日志文档输出格式-->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %X{requestId} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset>
        </encoder>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${LOG_FILE_PATH}/error-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>100MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录ERROR级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>ERROR</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 使用异步，一个AsyncAppender只能添加一个appender-ref -->
    <appender name="ASYNC_DEBUG_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="DEBUG_FILE"/>
    </appender>
    <appender name="ASYNC_INFO_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="INFO_FILE"/>
    </appender>
    <appender name="ASYNC_WARN_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="WARN_FILE"/>
    </appender>
    <appender name="ASYNC_ERROR_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="ERROR_FILE"/>
    </appender>

    <!-- 开启上面的appender -->
    <root level="info">
        <appender-ref ref="CONSOLE" />
        <appender-ref ref="ASYNC_DEBUG_FILE" />
        <appender-ref ref="ASYNC_INFO_FILE" />
        <appender-ref ref="ASYNC_WARN_FILE" />
        <appender-ref ref="ASYNC_ERROR_FILE" />
    </root>


</configuration>

2. Define a `complex` business process, Let’s take a look at the strength of the log

private final ExecutorService executorService = Executors.newFixedThreadPool(4);

@GetMapping("saveUser")
    public String saveUser() {
    log.info("进入了saveUser");
    // 异步
    CompletableFuture.runAsync(()-> b(), executorService);
    log.info("退出了saveUser");
    return "Ok";
}

private void b() {
    log.info("进入了b");
}

The log is as follows. You can see that the requestId of the asynchronous thread is lost. 21dbaad3-3158 This is the requestId. In this case, we need to customize the thread class to save the MDC context

2023-04-19 11:51:59.309 21dbaad3-3158 INFO 23044 --- [p-nio-80-exec-1] c.h.m.api.CompletableFutureApi : Entered saveUser
2023-04 -19 11: 51: 59.312 21DBAAD3-3158 Info 23044 --- [P-Nio-80-EXEC-1] C.H.M.API.COMPLETABLEFUTUREAPI: Exit Saveuser
2023-04-19 11: 51: 59.312 Info 23044- -- [pool-1-thread-1] c.h.m.api.CompletableFutureApi : Enter b

3. Define the thread implementation class and store the MDC context in the constructor

public static class MdcTaskWrapper implements Runnable {
    private final Runnable task;
    private final Map<String, String> contextMap;

    public MdcTaskWrapper(Runnable task) {
        this.task = task;
        this.contextMap = MDC.getCopyOfContextMap();
    }

    @Override
    public void run() {
        if (contextMap != null) {
            MDC.setContextMap(contextMap);
        }
        try {
            task.run();
        } finally {
            MDC.clear();
        }
    }
}

4. Next, rewrite how to use runAsync. We use MdcTaskWrapper to perform thread operations. This thread class contains the mdc context

@GetMapping("saveUser")
public String saveUser() {
    log.info("进入了saveUser");
    // 异步
    CompletableFuture.runAsync(this::b, command -> executorService.execute(new MdcTaskWrapper(command)));
    log.info("退出了saveUser");
    return "Ok";
}

private void b() {
    log.info("进入了b");
}

. As you can see, requestId: 4ab037ab-92cb, the asynchronous thread can get it. MDC context, and the link log is successfully recorded

2023-04-19 11:58:27.581 4ab037ab-92cb INFO 6816 --- [p-nio-80-exec-5] c.h.m.api .CompletableFutureApi : Entered saveUser
2023-04-19 11:58:27.582 4ab037ab-92cb INFO 6816 --- [p-nio-80-exec-5] c.h.m.api.CompletableFutureApi : Exited saveUser
2023 -04-19 11:58:27.582 4ab037ab-92cb INFO 6816 --- [pool-1-thread-1] c.h.m.api.CompletableFutureApi

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