Hi Dick,
On 11/25/08 07:26 AM, Dick Davies wrote:
> On Tue, Nov 25, 2008 at 6:05 AM, Shreedhar Ganapathy
> <Shreedhar.Ganapathy_at_sun.com> wrote:
>
>>> Ah, hadn't realised that; assumed session replication piggybacked on
>>> GMS traffic.
>>>
>>> Does that mean sessions do not go over multicast?
>>>
>>>
>> Sessions go over TCP when replication happens. Replication module does need
>> multicast to send out a query to the group as to who owns a particular
>> version of a given session. This typically happens during failover.
>>
>
> Thanks Shreedhar
>
> so just to clarify; when an instance gets a http request with a
> session it does not
> have the latest version of (determined by JSESSIONIDVERSION), it sends
> out a multicast
> request for it?
>
[1] Yes, but only after checking its replica cache to see if it contains
the session with the requested JSESSIONID and JSESSIONIDVERSION.
If found, it will activate its replica copy of the requested session,
and no multicast
will be sent out. Otherwise, a multicast will be sent.
> i.e. rather than instances pushing out sessions to their cluster
> peers, a server requests a session if it needs it and does not have it
> locally?
>
After having served a session (from its active cache), an instance will
push a replica
copy of the session (with incremented JSESSIONIDVERSION) to its replication
partner instance only, to enable [1].
Jan