JVM垃圾回收与一次线上内存泄露问题分析和解决过程

compile 'org.springframework.boot:spring-boot-starter-actuator'compile 'io.micrometer:micrometer-registry-prometheus'

management:  endpoints:      web:        exposure:          include: health,prometheus          默认报点的url：http://ip:port/actuator/prometheus

ps -ef|grep projectName

jmap -dump:live,format=b,file=dump.hprof <pid>

unzip -o MemoryAnalyzer-1.9.1.20190826-linux.gtk.x86_64.zipcd mat

./ParseHeapDump.sh <dump文件> org.eclipse.mat.api:suspects org.eclipse.mat.api:overview org.eclipse.mat.api:top_components

class关系链--ch.qos.logback.core.spi.AppenderAttachableImpl----ch.qos.logback.classic.Logger------org.slf4j.LoggerFactory--------ch.qos.logback.classic.LoggerContext----------org.slf4j.impl.StaticLoggerBinder

//com.huajiao.common.cron.service.CronServerService中的业务代码
//构造loggerLogger logger = org.slf4j.LoggerFactory.getLogger(cronBean.getClass());
//这里为了临时储存日志信息ListAppender<ILoggingEvent> listAppender = new ListAppender<>();((ch.qos.logback.classic.Logger)logger).addAppender(listAppender);listAppender.start();

//ch.qos.logback.classic.Logger中的代码public final class Logger implements org.slf4j.Logger ,... {    ...  transient private AppenderAttachableImpl<ILoggingEvent> aai;
  public synchronized void addAppender(Appender<ILoggingEvent> newAppender) {    if (aai == null) {      aai = new AppenderAttachableImpl<ILoggingEvent>();    }    aai.addAppender(newAppender);  }}

//ch.qos.logback.core.spi.AppenderAttachableImpl中的代码
public class AppenderAttachableImpl<E> implements AppenderAttachable<E> {
  @SuppressWarnings("unchecked")  final private COWArrayList<Appender<E>> appenderList = new COWArrayList<Appender<E>>(new Appender[0]);
  /**    * Attach an appender. If the appender is already in the list in won't be    * added again.  */  public void addAppender(Appender<E> newAppender) {    if (newAppender == null) {      throw new IllegalArgumentException("Null argument disallowed");    }    appenderList.addIfAbsent(newAppender);  }
    ...}

//org.slf4j.impl.StaticLoggerBinder中的关键代码public class StaticLoggerBinder implements LoggerFactoryBinder {//...省略部分代码
  private static StaticLoggerBinder SINGLETON = new StaticLoggerBinder();
  static {        SINGLETON.init();  }
  private boolean initialized = false;  private LoggerContext defaultLoggerContext = new LoggerContext();
  public static StaticLoggerBinder getSingleton() {    return SINGLETON;  }
  void init() {    try {      try {        new ContextInitializer(defaultLoggerContext).autoConfig();      } catch (JoranException je) {                Util.report("Failed to auto configure default logger context", je);      }      ....省略部分代码      initialized = true;    } catch (Exception t) { // see LOGBACK-1159            Util.report("Failed to instantiate [" + LoggerContext.class.getName() + "]", t);    }  }
  public ILoggerFactory getLoggerFactory() {    if (!initialized) {      return defaultLoggerContext;    }
    if (contextSelectorBinder.getContextSelector() == null) {      throw new IllegalStateException("contextSelector cannot be null. See also " + NULL_CS_URL);    }    return contextSelectorBinder.getContextSelector().getLoggerContext();  }

//构造loggerLogger logger = org.slf4j.LoggerFactory.getLogger(cronBean.getClass());
//这里为了临时储存日志信息ListAppender<ILoggingEvent> listAppender = new ListAppender<>();((ch.qos.logback.classic.Logger)logger).addAppender(listAppender);listAppender.start();try {  ....//此处省略部分业务代码} finally {//删除  ((ch.qos.logback.classic.Logger) logger).detachAppender(listAppender);   MDC.remove("tid");}