What are Sticky Sessions?

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What are Sticky Sessions?..

Answer / venky

Sticky sessions work with the load balancer to improve
efficiency of Persistent Sessions in a clustered configuration.

In a clustered configuration, the load balancer sends
requests to multiple backend Resin servers. Each session has
an owning Resin server and a backup Resin server. The load
balancer will send a session's request to the owning server
or to the backup if the owning server is not available. The
association of a session with a backend server is called
"sticky sessions".

Because the load balancing occurs before any interpretation
of the Virtual Host or Web Application, it's a <server>
configuration variable, with the <session-cookie> directive.

Sticky sessions encodes the session cookie with the owning
server. The encoding using a simple prefix value. 'a' refers
to the first server in the cluster, 'b' refers to the second
server, ..., 'z' refers to the 26th server.

So the session cookie JSESSIONID=cnn8x02mPph_4sOKlbn would
go to the third server, 192.168.0.12 in the following
configuration

<cluster>
<srun id="a" host="192.168.0.10" port="6802"/>
<srun id="b" host="192.168.0.11" port="6803"/>
<srun id="c" host="192.168.0.12" port="6803"/>
</cluster>