Request-based Sticky Session configuration with Spring Cloud LoadBalancer - spring-cloud

Question

I have the following configuration for request-based sticky session using Spring Cloud LoadBalancer
spring:
cloud:
discovery.client.simple.instances:
say-hello:
- instanceId: say-hello1
uri: http://localhost:8080
- instanceId: say-hello2
uri: http://localhost:8081
loadbalancer:
configurations: request-based-sticky-session
sticky-session:
add-service-instance-cookie: true
server.port:9090
the following call:
$ http :9090/hi 'Cookie:sc-lb-instance-id=say-hello1'
should go only to the say-hello1 instance based on the Request-based Sticky Session for LoadBalancer but instead is using round robin load balancing.
What do I miss here?
Here is the source code to try it: https://github.com/altfatterz/client-side-loadbalancing

Answer 1

There are 2 things to consider here:
In the sample, the cookie has to be passed on to the actual load-balanced request, for example like so:
#GetMapping("/hi")
public String hi(#RequestParam(value = "name", defaultValue = "Mary") String name) {
logger.info("Accessing /hi endpoint");
HttpHeaders headers = new HttpHeaders();
headers.set("Cookie", "sc-lb-instance-id=say-hello1");
HttpEntity entity = new HttpEntity(headers);
ResponseEntity<String> greeting = restTemplate.exchange("http://say-hello/greeting", HttpMethod.GET, entity, String.class, new HashMap<>());
return greeting + " " + name;
}
This feature is only supported for WebClient-backed load-balancing. It was not properly documented. I have documented it here.
I have also created a GitHub issue for adding the non-reactive implementation, however, the decision to implement it will be dependant on larger community interest.