On 2017/11/16 18:05, Gang He wrote: > Hello Changwei, > > Base on your description, it looks make sense. > Since I uses fs/dlm kernel module, it looks stable. > Do you compare both dlm implementation? maybe can learn from each other. > > > Thanks > Gang
Hi Gang, Actually , I have studied some code of fs/dlm and I don't think it can handle such a exception scenario. But I don't have a test environment with fs/dlm applied. Can you take some tests like configuring a duplicated IP address to a host. I think it is easy to reproduce. Thanks, Changwei > > >>>> >> Hi all, >> As far as we know, ocfs2/o2net is not a reliable message mechanism. >> Messages might get lost due to a sudden TCP socket connection shutdown. >> And the only customer of o2net is ocfs2/dlm, so this may cause ocfs2/dlm >> hang(missing AST and ASSERT MASTER). Sometimes it also causes >> ocfs2/dlm's infinite wait for accomplishment of DLM recovery. But that >> won't happen since target node is still heartbeating and no dlm recovery >> procedure will be launched. >> >> So I think above cases drive us to improve current ocfs2/o2net making it >> more reliable. I already have a draft design for it. And we indeed need >> to change o2net behavior. >> >> To accomplish this goal, we tag each o2net message with a sequence >> ::msg_seq to let receiver tell if the newly coming message is a >> duplicated one or not and ::msg_seq will work as a key value for >> searching a following key structure in a red-black tree. >> >> A brandy new structure is added to o2net named as *Message Holder*, it >> is responsible for _handle_status_ storing. >> >> When TCP has to shutdown or reset due to unknown reason, although we >> lose the packets in send or receive buffer, o2net still manages those >> messages. This gives a chance to o2net to re-send the messages once TCP >> connection is established again. >> >> Below diagram demonstrates how it works: >> >> SEND RECV >> send message >> tag message header with ::msg_seq >> search for Message Holder with >> ::msg_seq >> NOT FOUND - insert one >> (FOUND - means a duplicated one) >> handle message >> store status into Message Holder >> send back status >> instruct RECV to remove MH >> notify SEND that MH is already >> removed >> return to caller >> >> I am expecting your comments especially from @Mark, @Joseph and @Junxiao. >> >> Thanks, >> Changwei. >> >> _______________________________________________ >> Ocfs2-devel mailing list >> Ocfs2-devel@oss.oracle.com >> https://oss.oracle.com/mailman/listinfo/ocfs2-devel > > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel
