Unable to get variable from Lookup cache from two proxies

Google Cloud Apigee
1

Hello There,

I’m facing an issue where I’m unable to get a cached value using lookup cache policy as explained below:

I have two proxies (proxy1 and proxy2) that are deployed under same API product and each proxy hit a different target endpointpoint:

Proxy1 : calls authenticate API.

Proxy2 : calls accounts API

In proxy1, once I get the response back, I’m caching the token using the below polices in sequence to the response flow:

ExtractVariables:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ExtractVariables async="false" continueOnError="false" enabled="true" name="Extract_IAM_Token">
    <DisplayName>Extract IAM Token From IAM Response</DisplayName>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <JSONPayload>
        <Variable name="AccessToken">
            <JSONPath>$.access_token</JSONPath>
        </Variable>
        <Variable name="AccessTokenType">
            <JSONPath>$.token_type</JSONPath>
        </Variable>
        <Variable name="AccessTokenExpiry">
            <JSONPath>$.expires_in</JSONPath>
        </Variable>
        <Variable name="AccessTokenScope">
            <JSONPath>$.scope</JSONPath>
        </Variable>
    </JSONPayload>
    <Source clearPayload="false">response</Source>
    <VariablePrefix>varIAMToken</VariablePrefix>
</ExtractVariables>

PopulateCache:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<PopulateCache async="false" continueOnError="false" enabled="true" name="IAM_MG_Token">
    <DisplayName>Populate IAM Token From Cache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment>mgAccessToken</KeyFragment>
        <KeyFragment ref="apigee.access_token"/>
    </CacheKey>
    <Scope>Exclusive</Scope>
    <ExpirySettings>
        <TimeoutInSec>3600</TimeoutInSec>
    </ExpirySettings>
    <Source>varIAMToken.AccessToken</Source>
</PopulateCache>

LookupCache (used to confirm that I can get the token):

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<LookupCache async="false" continueOnError="false" enabled="true" name="Get_IAM_Token">
    <DisplayName>Lookup IAM Token From Cache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment>mgAccessToken</KeyFragment>
        <KeyFragment ref="apigee.access_token"/>
    </CacheKey>
    <Scope>Exclusive</Scope>
    <AssignTo>varIAMToken.AccessToken</AssignTo>
</LookupCache>

AssignMessage:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage async="false" continueOnError="false" enabled="true" name="Return_MG_Token">
    <DisplayName>Remove IAM Token From the Response Body</DisplayName>
    <Set>
        <Payload contentType="application/json">
            {
                "AccessToken":"{varIAMToken.AccessToken}"
            }
        </Payload>
        <StatusCode>200</StatusCode>
        <ReasonPhrase>OK</ReasonPhrase>
    </Set>
    <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
</AssignMessage>

Which gives me the token. However, for proxy2, I need to lookup the cache so I can make the call to my accounts API with that token. I’m adding the below policy to the request flow :

LookupCache:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<LookupCache async="false" continueOnError="false" enabled="true" name="Get_IAM_Token">
    <DisplayName>Lookup IAM Token From Cache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment>mgAccessToken</KeyFragment>
        <KeyFragment ref="apigee.access_token"/>
    </CacheKey>
    <Scope>Global</Scope>
    <AssignTo>varIAMToken.AccessToken</AssignTo>
</LookupCache>

However, I’m not getting the token back and the cache comes empty.

6720-screen-shot-2018-04-06-at-33617-pm.png
6720-screen-shot-2018-04-06-at-33617-pm.png1974×450 37.3 KB

I’m not sure why am i missing in my polices or if i’m doing something incorrect. I really appreciate your help.

Thank you

1 Like
2

THANKS for the clear, detailed question! With all that detail, it makes it really easy for us to understand what’s going on.

Answer: check the Scope.

In one of your LookupCache policies, you have

<Scope>Global</Scope>

In the other LookupCache and in the PopulateCache, you have

<Scope>Exclusive</Scope>

I think you want Global scope, everywhere.

The scope must match, across Populate and Lookup. Internally, the PopulateCache or LookupCache will use a different key if you specify Scope= Exclusive vs Global. Another way to say this: If you use PopulateCache with Exclusive scope, a lookup with Global scope will not retrieve the value you just populated.

Also, according to the documentation for the LookupCache policy, a value populated with Exclusive scope would be available only to a LookupCache policy operating in the same proxyEndpoint of the same revision of the same proxy bundle! Therefore if you use PopulateCache in proxy1 with Scope=Exclusive, you cannot retrieve from proxy2 with LookupCache, regardless of what you use for Scope.

I think you want to use Global Scope, in every policy. With that, values populated in proxy1 would be available for lookup from proxy1 or proxy2.

3

Thank you so much for your response. I update the Scope and faced the same issue. However, The thing I didn’t mention in my issue is that I was using Flow Callout policy to do shared-double-proxy between my Apigee Edge and MicroGatway. This policy (Internally) was doing “add cache” between my “apigee.access_token” and my micorgateway token causing that I lost “varIAMToken.AccessToken” from the cache since it is overriding it as I’m using the same key.

To solve the issue I had to first lookup my cache (using Lookup cache policy) in my account proxy before doing the double-shared-porxy. Then after the flow callout policy, I’m re-populating the cache with “apigee.access_token”/“varIAMToken.AccessToken” which solved my issue.