Session affinity is configured at the backend service level. It allows requests by a client to a backend service to always be routed to the same origin. This is also known as "sticky sessions" and is useful in situations where some state is stored server-side (i.e., with stateful services) and sessions are not shared between instances (origins).
Session affinity in Styx is cookie-based: for each backend service configured to use sticky sessions, the client receives a cookie. The value of the cookie tells Styx which origin to route to. If the client has no cookie, an origin will be assigned by the load balancer. Once they have a cookie, they will be routed to the origin it specifies.
If Styx is unable to route to the specified origin, the load balancer will choose a new origin, and the client's cookie will be overwritten with the new value.
The Session Affinity is configured per backend service via the
stickySession block inside the Backend Service block.
stickySession:
enabled: true
timeoutSeconds: 14321