Response Cache policy for conditional flows

Google Cloud Apigee
1

Question:

I am using response cache in conditional flow to cache data from a backend resource, reducing the number of requests to the resource.

I have 4 conditional flow and added in both request & response step as below.

<?xml version="1.0" encoding="UTF-8"?>
<Flow name="1">
   <Description />
   <Request>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Request>
   <Response>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Response>
   <Condition>(proxy.pathsuffix MatchesPath "/1")</Condition>
</Flow>

<?xml version="1.0" encoding="UTF-8"?>
<Flow name="2">
   <Description />
   <Request>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Request>
   <Response>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Response>
   <Condition>(proxy.pathsuffix MatchesPath "/2")</Condition>
</Flow>


<?xml version="1.0" encoding="UTF-8"?>
<Flow name="3">
   <Description />
   <Request>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Request>
   <Response>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Response>
   <Condition>(proxy.pathsuffix MatchesPath "/3")</Condition>
</Flow>

<?xml version="1.0" encoding="UTF-8"?>
<Flow name="4">
   <Description />
   <Request>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Request>
   <Response>
      <Step>
         <Name>Response-Cache-1</Name>
      </Step>
   </Response>
   <Condition>(proxy.pathsuffix MatchesPath "/4")</Condition>
</Flow>

==

<?xml version="1.0" encoding="UTF-8"?>
<ResponseCache async="false" continueOnError="false" enabled="true" name="Response-Cache-1">
   <DisplayName>Response-Cache-1</DisplayName>
   <FaultRules />
   <Properties />
   <CacheKey>
      <Prefix />
      <KeyFragment ref="request.uri" type="string" />
   </CacheKey>
   <Scope>Exclusive</Scope>
   <ExpirySettings>
      <ExpiryDate />
      <TimeOfDay />
      <TimeoutInSec ref="">300</TimeoutInSec>
   </ExpirySettings>
   <SkipCacheLookup />
   <SkipCachePopulation />
</ResponseCache>

==

What I was expecting:

##################

Cache the data from backend resource for each conditional flow & respond from cache( for subsequent requests).

What I am facing:

###############

See below error.

Response cache step definition Response-Cache-1 can not be attached more than once in the response path

We are using on-prem 4.15.04.

Tried few options to apply the policy in proxy pre/ & target post flow but see same error.

Let me know your suggestions if any one used response cache with conditional flows?

-Vinay

1 Like
2

Hi @vinay poreddy looks like from your XML fragment that you want to cache the response when either of the 4 flows occur. If that is the case could you not have 4 conditions in one flow? This could work unless you are doing other things in those flows that are different from each other. Another alternative is use Populate / Lookup Cache policies for more explicit control.

1 Like
3

@vinay poreddy , Just FYI, Moving forward while posting any code, use code widget in text editor & format xml code using tools like http://www.freeformatter.com/xml-formatter.html . That will help to improve readability & visibility. Thank you :slight_smile: I have done same for now.

4

@vinay poreddy , Great Question & Thank you for asking same. I never know about this design restriction & your question helped me to learn about same.

It’s by design, see the documentation here that explains same in error codes section.

2598-screen-shot-2016-04-29-at-102456-am.png
2598-screen-shot-2016-04-29-at-102456-am.png1496Ă—444 49.7 KB

So, Please change your flow condition to match that / use step condition in preflow / postflow instead of flow conditions. Do you know you can conditionally execute policies using step conditions ? Step conditions is the easy way to solve your issue.

@docs , Can we also add this information in policy description “Where” section to avoid confusion ? Right now, it’s only visible in error codes section. Thank you :slight_smile:

1 Like
5

@vinay poreddy

Can you please try the below solution?

  1. I am assuming that you are also having one condition for unknown resource i.e. if path suffix does not matches /1, /2, /3. /4

  2. Use the cache policy in the PROXY POSTFLOW and add the KEYFRAGMENT with proxy path suffix

This will resolve the issue. Please let me know if this method is incorrect

6

I tested using Proxy Endpoint Response flow and it took care of any target endpoint it hit.

I have other issues which made a decision to remove the caching policy but good to explore response caching policy.

7

@vinay poreddy , Glad to know that. If above answer resolved your query, please click on accept link below the answer so that it will be helpful for other users too. Thank you.

8

this is a great work around, but it does make me wonder: are caching and conditional flows mutually exclusive?

maybe this should be logged as a bug?

9

@Benjamin Goldman , I don’t see any reason why we cannot add multiple response cache policies in conditional flows until unless i am missing something that i don’t know.

Yes, As you said, Looks like a bug for me. Ideally, It should override other caches if added multiple times. I have raised a bug in Jira - MGMT-3395 .

10

Hi @Anil Sagar, Any luck with this issue? We have a use case to implement response caching limited to only some condition flows. I’m unable to attach ResponseCache policy to multiple conditional flows. Thanks in advance :slight_smile: