Flow variable for lookup cache policy which tells the elapsed time of the cached entry

[#1]

There is a need for my proxy to know how long a cached entry was put into Cache by Populate cache policy. Is there flow variable available after executing lookup Cachce to find the elapsed time when a cahce hit occurs?.

[sarthak]

Hi @murali boyapati I do not recall any flow variable on top of my head which stores what you are looking for.

But I think you can build the functionality :

When you construct the cache key ... append a current timestamp as well. So your Populate Cache policy should have one of the key fragments as follows :

<KeyFragment ref="keyFrag1"/>

<KeyFragment ref="KeyFrag2"/>

<KeyFragment ref="system.timestamp"/>

Put that as the last key fragment.

When you do the key lookup do like this :

<CacheKey> 

<Prefix/> 

<KeyFragmentref="KeyFrag1"/>

<KeyFragmentref="KeyFrag2"/> 

</CacheKey>

So basically do not do the lookup based on the timestamp keyfragment.

Once retrieved , check the timestamp against the lookupcache.{policy-name}.cachekey flow variable using javascript or python policy.

I havn't tried this out yet, but I think this should work. Let me know what you find out.

Directly using the system.timestamp will give a class cast exception for not being able to cast from long to string. To avoid that I added a javascript policy just before the populate Cache policy:

context.setVariable("current_sys_time_in_string",context.getVariable("system.timestamp").toString());

And then in the populate lookup cache policy use "current_sys_time_in_string" .

Thanks

Sarthak

[#3]

@sarthak I will try this and update on the result soon.

[#4]

@sarthak Tried by adding <KeyFragment ref="system.time"/> as system.timestamp is giving cast exception as it is Long. But lookup cache policy is allays failing to hit the cache as the keys doesn't match now. do I need to specify anything on the lookup cache policy to look for only partial match of the key?

[sarthak]

Yes I see the error. I updated the answer with the solution

[#6]

I tried this and same issue as the Lookup key is not matching, it never identifying the cached object. So my policy is always returning cache hit as "false".

[sarthak]

Yes you are right. You can do deletion of caches in a cascading manner but probably not a select. I am checking a few things and I will update if I find a viable solution.

[sarthak]

@murali boyapati After thinking about it more I don't think the above approach will work. It might be possible to store the cache key and them current timestamp in a KVM map . And then use the KVM policy to check for the time just before the caching policy is executed.

Let me know what do you think about that approach ?

[#9]

Instead of KVM I implemented using another populate cache policy to just store the timestamp and whenever a cache hit on the main cachekey I will look for cached timestamp using timestamp cachekey.