Tomcat非容器线程中的Java异常处理

Question

我在catalina日志中具有以下堆栈跟踪：

24-Jan-2019 16:44:13.139 INFO [messageBrokerScheduler-3] org.apache.coyote.AbstractProcessor.setErrorState An error occurred in processing while on a non-container thread. The connection will be closed immediately
 java.io.IOException: An existing connection was forcibly closed by the remote host
        at sun.nio.ch.SocketDispatcher.write0(Native Method)
        .....
        at org.apache.catalina.connector.ResponseFacade.flushBuffer(ResponseFacade.java:312)
        at org.springframework.http.server.ServletServerHttpResponse.flush(ServletServerHttpResponse.java:96)
        at org.springframework.web.socket.sockjs.transport.session.AbstractHttpSockJsSession.writeFrameInternal(AbstractHttpSockJsSession.java:350)
        at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession.writeFrame(AbstractSockJsSession.java:322)
        at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession.sendHeartbeat(AbstractSockJsSession.java:255)
        at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession$HeartbeatTask.run(AbstractSockJsSession.java:456)
        at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

从堆栈跟踪中可以看出，AbstractSockJsSession $ HeartbeatTask.run（AbstractSockJsSession.java:456）中有一个例外

从spring-websocket源代码中，我们有以下内容：

private class HeartbeatTask implements Runnable {

    private boolean expired;

    @Override
    public void run() {
        synchronized (responseLock) {
            if (!this.expired && !isClosed()) {
                try {
                    sendHeartbeat();
                }
                catch (Throwable ex) {
                    // Ignore: already handled in writeFrame...
                }
                finally {
                    this.expired = true;
                }
            }
        }
    }

    void cancel() {
        this.expired = true;
    }
}

可以看出，sendHeartbeat（）方法由try-catch块包装。

所以，不明白，tomcat如何打印该异常？

我正在使用spring-websocket 4.3.8，tomcat 8.5.9

JFYI：
我知道spring-websocket 4.3.8版本中添加了catch块，这就是为什么我使用4.3.8的原因
我也知道在Tomcat 8.5.25中，setErrorState以调试模式记录消息。