How should the Cache-Control to work in conjunction with the ResponseCachePolicy?

Google Cloud Apigee
1

After reading the documentation here, came across the setting UseResponseCacheHeaders. If I understand this right, if I set the appropriate Cache-Control header and Expires header, the cache will honor the value set here and expire the resource accordingly. But this is not working as expected.

On the Target PostFlow Response, I set the headers by means of a JavaScript policy, below is the code:

var now = new Date().getTime();
var ttl = 10 * 1000;
var then = now + ttl;
var thenDate = new Date(then);
context.setVariable("response.header.Expires",thenDate.toUTCString());
context.setVariable("response.header.Cache-Control","max-age="+ttl);

The ResponseCachePolicy is attached at the Response of one of my Flows as below, including the policy XML as well:

Proxy Flow XML:

<Flow name="getCache">
            <Description/>
            <Condition>request.verb = "GET" AND proxy.pathsuffix MatchesPath "/getCache"</Condition>
            <Request>
                <Step>
                    <Name>ResponseCache</Name>
                </Step>
            </Request>
            <Response>
                <Step>
                    <Name>ResponseCache</Name>
                    <Condition>response.status.code = 200</Condition>
                </Step>
            </Response>
 </Flow>

Cache Policy:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ResponseCache async="false" continueOnError="false" enabled="true" name="ResponseCache">
    <DisplayName>ResponseCache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment>getCache</KeyFragment> <!-- hard coded flow identifier -->
        <KeyFragment ref="accesstoken.attribute1"/>
        <KeyFragment ref="accesstoken.attribute2"/>
    </CacheKey>
    <Scope>Global</Scope>
    <CacheResource>cache-resource</CacheResource>
    <!--ExpirySettings>
        <TimeoutInSec ref="">3600</TimeoutInSec>
    </ExpirySettings--> <!-- tried commenting/uncommenting this -->
    <SkipCacheLookup>request.header.Cache-Control = "no-cache"</SkipCacheLookup> <!-- this works as expected and by passes the cache and hits the target -->
    <SkipCachePopulation/>
    <UseResponseCacheHeaders/> <!-- This does not work as expected -->
</ResponseCache>

Any thoughts/suggestions appreciated.

Thanks,

Girish

1 Like
2

Dear @Girish Gajria,

As per the documentation here, you need to set the <UseResponseCacheHeaders> element value to true to be able to use the response headers “Cache-Control” and “Expires”. Your comment in the Cache policy about this tag states “This does not work as expected”. Not sure what your experiments were about this tag.

Anyways, I would like to check the following:

Have you tried setting [<UseResponseCacheHeaders>](http://docs.apigee.com/api-services/reference/response-cache-policy#UseResponseCacheHeaders)to true ? If not, can you please set it to true and check the behaviour ?

Note: The element[<UseResponseCacheHeaders>](http://docs.apigee.com/api-services/reference/response-cache-policy#UseResponseCacheHeaders)is false by default.

Regards,

Amar

3

You might want to read the following document - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control

There are a bunch of Cache-Control values that the client can send in a HTTP request. For example ‘max-age’, ‘max-stale’. Therefore instead of checking for:

request.header.Cache-Control = "no-cache"

You may need to use a Javascript callout to find the ‘no-cache’ value from the list of Cache-Control headers.