Populate Cache fails

[AMetelski]

Hello, 

I'm trying to populate a cache with the results of a service call, but when the flow attempts to store the value I get this error. 

error.class state type error Identifier 

Properties

java.lang.ClassCastException

PROXY_REQ_FLOW

ErrorPoint

class com.apigee.flow.Variables cannot be cast to class com.apigee.entities.info.TargetInfo (com.apigee.flow.Variables and com.apigee.entities.info.TargetInfo are in unnamed module of loader 'app')

fault

[dchiesa1]

Hi, sorry about that error message. That does not sound particularly helpful. 

Can you show your PopulateCache policy configuration please?

[AMetelski]

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<PopulateCache continueOnError="false" enabled="true" name="pc-access-token">
    <DisplayName>pc-access-token</DisplayName>
    <CacheResource>defaultCustomer</CacheResource>
    <CacheKey>
        <KeyFragment>token</KeyFragment>
    </CacheKey>
    <Scope>Exclusive</Scope>
    <ExpirySettings>
        <TimeoutInSec>60</TimeoutInSec>
    </ExpirySettings>
    <Source>accessToken</Source>
</PopulateCache>

And here is the extract variable right before the PC. 

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ExtractVariables continueOnError="false" enabled="true" name="ev-login-response">
    <DisplayName>ev-login-response</DisplayName>
    <Properties/>
    <Source>loginResponse</Source>
    <JSONPayload>
        <Variable name="accessToken" type="string">
            <JSONPath>$.access_token</JSONPath>
        </Variable>
        <Variable name="apiUrl" type="string">
            <JSONPath>$.instance_url</JSONPath>
        </Variable>
    </JSONPayload>
</ExtractVariables>

[dchiesa1]

Wow, that looks pretty basic. I am surprised you are having trouble with that. Let me try it here.

EDIT

OK I tried ... basically the same thing from here and... it just works. Attached please find a working API Proxy.

It does this:

• check the cache for a stored value

• if none is found

  • Use ServiceCallout to invoke an external system, getting a JSON response
  • Use ExtractVariables to extract a few fields from the response.
  • Use PopulateCache to load one of those values into the cache
  • Use AssignMessage to load the cached value into a well-known variable.
• invoke a backend endpoint
• in the response, insert the cached value as a header

[AMetelski]

Yeah, it's pretty basic. The issue ended up being in my assign message policy earlier in the flow.

Besides setting continueOnError = false Is there anything else I can do to make sure exceptions are bubbling up sooner?

[dchiesa1]

I'd advise you to just omit continueOnError completely. It defaults to false, which is usually what you want. 

And ... nope, nothing further for you to do.  Setting continueOnError to false , or omitting it completely, is what you need to do to let exceptions surface at the earliest possible point. 

[joe_zennioptica]

I encountered the same issue, do you mind sharing what you did to fix it?

[AMetelski]

@joe_zennioptica, I don't recall the exact fix, but there was a missing configured assign message before the cache policy that was causing the fault. 

[oleksandrdarchu]

I had same issue. As mentioned above, root cause was in the assign variable. In my case I was trying to assign target.copy.pathsuffix in the proxy with no target.

Once that part had been commented, everything started to work

It is still unclear why

- same code works well in Edge

- Issue is caused by incorrectly assigned variable, but the error actually happens only if there is a populate cache activity after such assign. 

Still the error makes some sense --  looks like target variable was not initialized without having actual target in the proxy, so assigning something there was incorrect

Hope this helps