We're using Logback in high transactional system.
In some cases, our JVM memory abnormally increased and after some minutes, clients could not connect to our services.

Here is dump of JVM threads.
I think there is a problem on logback.

"pool-9-thread-1257" prio=10 tid=0x00002ab04d8c4000 nid=0x6613 waiting for monitor entry [0x000000004ec13000]
java.lang.Thread.State: BLOCKED (on object monitor)
at ch.qos.logback.core.AppenderBase.doAppend(AppenderBase.java:64)

• waiting to lock <0x00002aab31180628> (a ch.qos.logback.classic.sift.SiftingAppender)
  at ch.qos.logback.core.spi.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:64)
  at ch.qos.logback.classic.Logger.appendLoopOnAppenders(Logger.java:283)
  at ch.qos.logback.classic.Logger.callAppenders(Logger.java:270)
  at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:471)
  at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:425)
  at ch.qos.logback.classic.Logger.debug(Logger.java:532)
  at com.kishware.common.log.Slf4jLogger.debug(Slf4jLogger.java:47)
  at com.kishware.core.framework.controller.PreOperationController.preOperationControl(PreOperationController.java:109)
  at com.kishware.core.framework.controller.PreOperationController$1.call(PreOperationController.java:73)
  at com.kishware.core.framework.controller.PreOperationController$1.call(PreOperationController.java:1)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
  at java.util.concurrent.FutureTask.run(FutureTask.java:138)
  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
  at java.lang.Thread.run(Thread.java:619)