Microsoft Azure API Management - Cache policy doesn't work

Question

I have tried to set a caching policy in Azure API Management as follows:

<policies>
    <inbound>
        <base />
        <cache-lookup vary-by-developer="false" vary-by-developer-groups="false" must-revalidate="true" downstream-caching-type="none" caching-type="internal">
            <vary-by-query-parameter>KontoNr</vary-by-query-parameter>
        </cache-lookup>
        <set-backend-service id="apim-generated-policy" backend-id="LogicApp_GeldEinzahlen_APIM_f597e3433e7847cb9d689c3f95bf1d6d" />
        <validate-jwt header-name="Authorization" failed-validation-httpcode="401" failed-validation-error-message="Unauthorized. Access token is missing or invalid.">
            <openid-config url="https://login.microsoftonline.com/1b7c4ba5-7701-49e7-94d8-5ddbc87f8b6e/v2.0/.well-known/openid-configuration" />
            <required-claims>
                <claim name="aud">
                    <value>7068cdb6-0e5c-49c5-aaa8-ec8fc941de22</value>
                </claim>
            </required-claims>
        </validate-jwt>
        <set-variable name="isKontoNr" value="@(context.Request.MatchedParameters["kontoNr"].ToString().Length != 10)" />
        <choose>
            <when condition="@(context.Variables.GetValueOrDefault<bool>("isKontoNr"))">
                <return-response>
                    <set-status code="400" reason="Bad Request" />
                    <set-header name="WWW-Request" exists-action="override">
                        <value>Generell error="kontoNr invalid"</value>
                    </set-header>
                </return-response>
            </when>
        </choose>
    </inbound>
    <backend>
        <base />
    </backend>
    <outbound>
        <base />
        <cache-store duration="1000" />
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>

I have pricing tier "Developer" so the internal cache has to be available but if i make a request i always get the following response:

HTTP/1.1 200 OK

cache-control: no-cache
content-encoding: gzip
content-type: text/plain; charset=utf-8
date: Tue, 12 Jan 2021 15:54:26 GMT
expires: -1
pragma: no-cache
strict-transport-security: max-age=31536000; includeSubDomains

cache-control is always 'no-cache' no matter what i send in the header.

How can i fix it ? Is some other configuration needed or have i enable something?

the no-cache pragma should not really be indicative whether the cache was being used. Go to the testing page in APIM, run a query and look a the traces. There you will see whether cache lookup was used — silent
Hi Pascal, if the answer I provided below helps your question, could you please mark(click on the check mark beside my answer to toggle it from greyed out to filled in) it as "accepted", thanks in advance. — Hury Shen

Hury Shen Hury Shen · Accepted Answer · 2021-01-13T02:17:04

As silent mentioned in comments, the message cache-control: no-cache should not really be indicative whether the cache was being used. The <cache-lookup> policy is correct in your APIM.

When you request the api(for test in APIM page) first time, click "Trace" --> "Inbound". You can find the message Cache lookup resulted in a miss because there is no cache when you request first time.

And then click "Outbound", you can find Response will be buffered during streaming and stored in the cache after it is received in full.

Then, since you specified the cache be stored for 1000 seconds, so if you request again in 1000 seconds, you can find the message Cache lookup resulted in a hit! under "Inbound".

Please test in your side, and if the result is same with what I mentioned above, the policy <cache-lookup> works fine in your APIM.

Microsoft Azure API Management - Cache policy doesn't work

1 Answers