>>>
> 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.
Do you have a detailed steps to reproduce this problem? I think the problem
should exist,
Maybe the idea can be referenced by both dlm modules.
Second, if you add this message-id and red-black tree mechanism, you also need
to
add a monitor kernel-thread, to see if these messages in red-black tree will
become more and more bigger (this will lead to memory leak).
Thanks
Gang
>>
>>
>> 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 at oss.oracle.com
>>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>
>>