Rs shut down because of DroppedSnapshotException when memstore flushing

After memstore be flushed, flush marker will be writed to WAL.
But current wal being rolled now, the DroppedSnapshotException will happen.

if (wal != null)

{ // write flush marker to WAL. If fail, we should throw DroppedSnapshotException FlushDescriptor desc = ProtobufUtil.toFlushDescriptor(FlushAction.COMMIT_FLUSH, getRegionInfo(), flushOpSeqId, committedFiles); WALUtil.writeFlushMarker(wal, this.htableDescriptor, getRegionInfo(), desc, sequenceId, true); }

} catch (Throwable t) {
.......

DroppedSnapshotException dse = new DroppedSnapshotException("region: " +
Bytes.toStringBinary(getRegionName()));
dse.initCause(t);
status.abort("Flush failed: " + StringUtils.stringifyException(t));
throw dse;