HTTP caching fails after initial Max Age expiry

[chamil321]

Description:

$subject and hits the backend rather taking the caches response. The issue lies with the age calculation

Steps to reproduce:

import ballerina/http;
import ballerina/log;

http:Client cachingEP = checkpanic new ("http://localhost:8080",
                             {cache: {enabled: true, isShared: true}});
service /cache on new http:Listener(9090) {

    resource function get .(http:Caller caller, http:Request req) {
        http:Response|error response = cachingEP->forward("/hello", req);

        if (response is http:Response) {
            var result = caller->respond(response);
            if (result is error) {
                log:printError("Failed to respond to the caller", result);
            }
        } else {
            http:Response res = new;
            res.statusCode = 500;
            res.setPayload(response.message());
            var result = caller->respond(res);
            if (result is error) {
                log:printError("Failed to respond to the caller", result);
            }
        }
    }
}



service /hello on new http:Listener(8080) {

    resource function 'default .(http:Caller caller, http:Request req) {
        json payload = {"message": "Hello, World!"};
        http:Response res = new;
        http:ResponseCacheControl resCC = new;
        resCC.maxAge = 15;
        resCC.mustRevalidate = true;
        resCC.isPrivate = false;

        res.cacheControl = resCC;

        res.setETag(payload);
        res.setLastModified();

        res.setPayload(payload);

        var result = caller->respond(res);
        if (result is error) {
            log:printError("Failed to respond to the caller", result);
        }
    }
}

Invocation 1 : Hit backend : 200 OK response
Invocation 2 : Within max age : Take from cache
Invocation 3 : After max age timeout : Hit backend : 304 Not modified response
Invocation 4 : Within 2nd max age : Hit backend : 304 Not modified response // this is problematic

Affected Versions:
SL beta 4