[keycloak-dev] Sticky sessions in backchannel requests

I was thinking about possibilities how to solve the issue with sticky sessions in backchannel requests. It seems that we need to support the scenarios, when backchannel requests won't be able to share the sticky session cookie with the browser. However in many cases it may be possible that backchannel requests can participate in the "sticky session", which will have great advantage for performance. Some thoughts: - OAuth code (the one used in code-to-token backchannel request) can be JWT signed by realm HMAC key. One of the claims in the code could be "route-id" - Refresh tokens will also contain "route-id" claim - Keycloak OIDC adapters will be able to read the "route-id" from the code and they will attach sticky session information to the single backchannel request. Hence the backchannel request will be able to participate in sticky session and will be properly routed by loadbalancer to the correct node. Same for requests using refresh token. - It seems we will need some flexibility how is the "sticky session" added to the request to support various loadbalancers (cookie, path-parameters etc). Maybe we need some SPI on adapter side? Or just some kind of expressions/tokens, which will help to configure how exactly will cookie/path parameter look like? - Keycloak.js adapter seems to be working already. Ajax requests are re-sending the browser cookies and they are available in backchannel endpoint on server-side. This is true even if AUTH_SESSION_ID cookie is httpOnly. I've tested with Firefox, Chrome, my mobile phone. Not sure if this is different in other browsers/devices (cordova etc)? - For SAML backchannel requests (backchannel logout), we can add the same to our own SAML adapters though. - If people use 3rd party adapters, they won't have this. However we can also have support for some loadbalancers to route the requests directly based on the content of the route-id inside code (or refresh token). In many cases, customers will already have established loadbalancer in their deployments. However some others might be starting their deployment from the scratch and we can suggest them to use some of our preferred loadbalancers though. I've checked that if wildfly+mod_cluster is used as loadbalancer, we have the flexibility to inject custom undertow handler, which will be able to look into JWT and add the route info to the HttpServerExchange, from where mod_cluster will read it. Maybe we can investigate this possibility in the other popular loadbalancers (nginx etc) ? So in summary: Backchannel requests won't be able to participate in sticky session just if: 3rd party adapter is used AND customer can't use our preferred loadbalancer. WDYT? Marek