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On 28.05.2013 0:31, Julian Anastasov wrote:
On Fri, 24 May 2013, Aleksey Chudov wrote:
May be better to modify the sync algorithm to synchronize only persistence
templates for these specific cases? Is it possible at all?
May be, with some flag and also sloppy_tcp. Then the
parametrized SH with netmask will do the same - we can avoid
the sync messages. Of course, with SH there is more risk
for imbalance and it can be exploited. Also SH requires
equal configuration for the real servers.
Currently we are using multiple active / standby server pairs and
synchronize them with each other. So half of the servers are constantly
doing nothing. We are searching how to use all the servers in active /
active mode while maintaining high availability and sessions persistence
in case of failure of one of the load balancers. Unfortunately the
proposed stateless scheme with SH scheduler and Sloppy TCP is not
suitable for as since we are using WLC and WRR schedulers. As you
mentioned SH scheduler has several drawbacks because of which we can not
use it. Also, we can not synchronize all connections between all
servers, since it would require a lot of memory and the search for such
a huge connection table is likely to be slower.
But we can solve the sync problem in such a way as done in the
conntrackd which allows filtering by flow state. The easiest option is
to make the filter only for IP_VS_CONN_F_TEMPLATE state. Thus if all the
load balancers will sync persistent templates with each other then even
if one of the load balancers fails most users will remain on the same
real servers. Of course without the full sync clients must reestablish
TCP connections, but for this case we can use Sloppy TCP to create a TCP
connection state on any TCP packet.
What do you think of this idea?
Regards,
Aleksey
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