Sticky session Ribbon rule in Zuul always has null request - spring-boot

Question

I am attempting to implement a sticky session load balancer rule in a Zuul proxy service. I am using the code from this example: https://github.com/alejandro-du/vaadin-microservices-demo/blob/master/proxy-server/src/main/java/com/example/StickySessionRule.java
I seem to have everything configured correctly, and the rule is triggering in my debugger, but the call to RequestContext.getCurrentContext().getResponse() always returns null, so the cookie is never found, so the rule never takes effect.
The rest of the Zuul config is working 100%. My traffic is proxied and routed and I can use the app fine, only the sticky session rule is not working.
Is there another step I am missing to get the request wired in to this rule correctly?
My route config:
zuul.routes.appname.path=/appname/**
zuul.routes.appname.sensitiveHeaders=
zuul.routes.appname.stripPrefix=false
zuul.routes.appname.retryable=true
zuul.add-host-header=true
zuul.routes.appname.service-id=APP_NAME
hystrix.command.APP_NAME.execution.isolation.strategy=THREAD
hystrix.command.APP_NAME.execution.isolation.thread.timeoutInMilliseconds=125000
APP_NAME.ribbon.ServerListRefreshInterval=10000
APP_NAME.ribbon.retryableStatusCodes=500
APP_NAME.ribbon.MaxAutoRetries=5
APP_NAME.ribbon.MaxAutoRetriesNextServer=1
APP_NAME.ribbon.OkToRetryOnAllOperations=true
APP_NAME.ribbon.ReadTimeout=5000
APP_NAME.ribbon.ConnectTimeout=5000
APP_NAME.ribbon.EnablePrimeConnections=true
APP_NAME.ribbon.NFLoadBalancerRuleClassName=my.package.name.StickySessionRule
The app:
#EnableZuulProxy
#SpringBootApplication
public class ApplicationGateway {
public static void main(String[] args) {
SpringApplication.run(ApplicationGateway.class, args);
}
#Bean
public LocationRewriteFilter locationRewriteFilter() {
return new LocationRewriteFilter();
}
}
EDIT: As requested, the code:
import com.netflix.loadbalancer.Server;
import com.netflix.loadbalancer.ZoneAvoidanceRule;
import com.netflix.zuul.context.RequestContext;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
/**
* #author Alejandro Duarte.
*/
public class StickySessionRule extends ZoneAvoidanceRule {
public static final String COOKIE_NAME_SUFFIX = "-" + StickySessionRule.class.getSimpleName();
#Override
public Server choose(Object key) {
Optional<Cookie> cookie = getCookie(key);
if (cookie.isPresent()) {
Cookie hash = cookie.get();
List<Server> servers = getLoadBalancer().getReachableServers();
Optional<Server> server = servers.stream()
.filter(s -> s.isAlive() && s.isReadyToServe())
.filter(s -> hash.getValue().equals("" + s.hashCode()))
.findFirst();
if (server.isPresent()) {
return server.get();
}
}
return useNewServer(key);
}
private Server useNewServer(Object key) {
Server server = super.choose(key);
HttpServletResponse response = RequestContext.getCurrentContext().getResponse();
if (response != null) {
String cookieName = getCookieName(server);
Cookie newCookie = new Cookie(cookieName, "" + server.hashCode());
newCookie.setPath("/");
response.addCookie(newCookie);
}
return server;
}
private Optional<Cookie> getCookie(Object key) {
HttpServletRequest request = RequestContext.getCurrentContext().getRequest();
if (request != null) {
Server server = super.choose(key);
String cookieName = getCookieName(server);
Cookie[] cookies = request.getCookies();
if (cookies != null) {
return Arrays.stream(cookies)
.filter(c -> c.getName().equals(cookieName))
.findFirst();
}
}
return Optional.empty();
}
private String getCookieName(Server server) {
return server.getMetaInfo().getAppName() + COOKIE_NAME_SUFFIX;
}
}

Answer 1

I think you are missing a PreFilter, like this:
import com.netflix.zuul.context.RequestContext;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import org.springframework.cloud.netflix.zuul.filters.support.FilterConstants;
public class PreFilter extends com.netflix.zuul.ZuulFilter {
#Override
public Object run() {
RequestContext ctx = RequestContext.getCurrentContext();
RequestContext.getCurrentContext().set(FilterConstants.LOAD_BALANCER_KEY, ctx.getRequest());
return null;
}
#Override
public boolean shouldFilter() {
return true;
}
#Override
public int filterOrder() {
return FilterConstants.SEND_RESPONSE_FILTER_ORDER;
}
#Override
public String filterType() {
return "pre";
}
}
Mark as Bean
#Bean
public PreFilter preFilter() {
return new PreFilter();
}
And use it in your rule
#Override
public Server choose(Object key) {
javax.servlet.http.HttpServletRequest request = (javax.servlet.http.HttpServletRequest) key;

Answer 2

RequestContext not working cause "hystrix.command.APP_NAME.execution.isolation.strategy=THREAD"