On 07/04/2015 21:46, Linus Brimstedt wrote:
> Hello,
> 
> We have a problem with SimpleTcpCluster and session replication.
> We have tested this in Tomcat 7 and 8 (latest versions) on Windows Server
> using latest revision of Hotspot JDK version 7, but checking the code it
> seems like this is not covered anyway.
> 
> The problem:
> Replication works well when servers start up, they get missing sessions and
> new sessions are replicated to all servers.
> If one server temporarily drops out of the cluster, for example because it
> gets unresponsive during deployment of new application, the sessions
> created during this time are not replicated.
> 
> We remove servers from load balancer several times a day to upgrade
> different applications, so this has become a big problem for us.
> 
> Once the server joins the cluster again, new sessions are replicated
> properly. Only sessions created during the unresponsive window are lost.
> 
> 
> I see two solutions:
> 1) Switch to a different session sharing  setup (redis, memcached, or
> similar). We would like to avoid this if possible, to avoid maintaining
> more services.
> 
> 2) Improve SimpleTcpCluster to resend lost sessions.
> We had a brief look at the code and realize it's a bit of work. Before we
> dig deeper into this, it'd be good to see if someone has any thoughts on
> this, other suggestions or ideas to remedy the situation.

1. Use the BackupManager rather than the DeltaManager. It also scales
better.

Mark


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