@Override
    protected void atHeadOfRingBufferEventHandlerAppend() {
      if (testWALTimout) {
        try {
          Thread.sleep(timeoutMIlliseconds + 1000);
        } catch (InterruptedException e) {
          throw new RuntimeException(e);
        }
      }
      super.atHeadOfRingBufferEventHandlerAppend();
    }
The {@link WAL#sync} would timeout and throws {@link WALSyncTimeoutIOException},when
{@link HRegion#doWALAppend} catches this exception it aborts the RegionServer.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestWALSyncTimeoutException.java