[Ocfs2-devel] [PATCH 3/3] o2net: correct keepalive message protocol

[Sunil Mushran]

How will it double? The node will send a keepalive only if it has
not heard from the other node for 2 secs.

Srinivas Eeda wrote:
> No harm, just doubles heartbeat messages which is not required at all.
>
> Sunil Mushran wrote:
>> What's the harm in leaving it in?
>>
>> Srinivas Eeda wrote:
>>> Each node that has this patch would send a O2NET_MSG_KEEP_REQ_MAGIC 
>>> every 2 seconds(default). So, nodes without this patch would always 
>>> receive a heartbeat message every 2 seconds.
>>>
>>> Nodes without this patch will send(respond) with 
>>> O2NET_MSG_KEEP_RESP_MAGIC for every keep alive packet they received. 
>>> So nodes with this patch will always receive a response message.
>>>
>>> So, in a mixed setup, both nodes will always hear the heartbeat from 
>>> each other :).
>>>
>>> thanks,
>>> --Srini
>>>
>>>
>>>
>>> Joel Becker wrote:
>>>  
>>>> On Thu, Jan 28, 2010 at 08:51:11PM -0800, Srinivas Eeda wrote:
>>>>     
>>>>>          case O2NET_MSG_KEEP_REQ_MAGIC:
>>>>> -            o2net_sendpage(sc, o2net_keep_resp,
>>>>> -                       sizeof(*o2net_keep_resp));
>>>>> +            /* Each node now sends keepalive message every
>>>>> +             * keepalive time interval. Hence no need for response
>>>>> +             */
>>>>>              goto out;
>>>>>           
>>>>     You still have to send the response.  Think about a mixed
>>>> environment where some nodes have this fix and some do not.  The older
>>>> software is still waiting on the response.
>>>>     The newer version can just ignore any responses it gets from
>>>> other nodes.  But it has to send responses out just in case the other
>>>> node is older.
>>>>     The only other alternative is to bump the o2net protocol
>>>> version, and that means the cluster has to be shut down to 
>>>> upgrade.  Not
>>>> a good choice.
>>>>
>>>> Joel
>>>>
>>>>       
>>>
>>>
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>>>   
>>
>