Hi Ruwan, On Mon, Jun 24, 2019 at 9:57 AM Ruwan Abeykoon <ruw...@wso2.com> wrote:
> Hi All, > WSO2 Cache is designed designed as a shared in-memory cache at the first > place. We have made some effort to make it "non-shared" local cache for > limited cases. However there are few problems due to some of the historical > design based on shared cache. > > a) Cache is expired at [1]. The cache entry is not cleared if the entry is > recently modified or accessed (depending on the configuration). This was > right decision on the shared cache. But have problems when we have local > cache. We need to implement absolute TTL on local cache (not done yet) > b) All caches go through single cleanup task. Each cache can be > initialized as ACCESSED or MODIFIED or none. None means each cache entry is > removed after given cache timeout of the relevant cache. > > So, > @Bhathiya Jayasekara <bhath...@wso2.com> > >>But they are removed after the configured cache timeout (individually > based on their lifespan) even when they are kept being used. That means the > ACCESSED type expiry is not honored, I assume. Is my understanding wrong? > If the cache is not initialized as ACCESSED, this this can happen. > But in the above Git link I have shared, it has used ACCESSED type. Something is missing there. Thanks, Bhathiya > > @Azeez Afkham <az...@wso2.com> > >>I suppose this was a change suggested by Ruwan to ensure that even if an > entry is in use, we don't keep it fresh forever and to forcefully remove it > after a period of time. This was implemented to address a particular edge > case. > This was not implemented yet. I plan to implement this in next IAM > release, as we are currently recommending local-cache for all IAM > deployment with invalidation messages. Invalidation messages may become > dead letter, thus we need TTL of local cache. > > > [1] > https://github.com/wso2/carbon-kernel/blob/4.5.x/core/javax.cache/src/main/java/org/wso2/carbon/caching/impl/CacheImpl.java#L941 > > > > Cheers, > Ruwan A > > On Mon, Jun 24, 2019 at 9:11 AM Afkham Azeez <az...@wso2.com> wrote: > >> I suppose this was a change suggested by Ruwan to ensure that even if an >> entry is in use, we don't keep it fresh forever and to forcefully remove it >> after a period of time. This was implementated to address a particular edge >> case. Ruwan should be able to give more details. >> >> On Mon, Jun 24, 2019, 12:53 AM Bhathiya Jayasekara <bhath...@wso2.com> >> wrote: >> >>> Hi Azeez/Nuwan, >>> >>> On Fri, Jun 21, 2019 at 2:57 PM Afkham Azeez <az...@wso2.com> wrote: >>> >>>> An item can get removed from the cache for two reasons: >>>> >>>> 1. Cache expiry. >>>> A task runs periodically and checks the last accessed time of each >>>> cache entry and removes it if the entry has not been accessed for sometime >>>> >>> >>> This is what I expected/assumed too. (i.e. if a particular cache entry >>> is kept being used forever, it should never be removed from cache [plz >>> correct me if my understanding of ACCESSED type expiry is wrong] ) And I >>> also have noticed that in some caches (I don't remember where) it runs a >>> forceful cache clean up task periodically to remove these never-removable >>> cache entries time to time. So that was the other part of my >>> expectation/assumption. >>> >>> However, I ran a few tests with APIM gateway cache[1] with just 2 >>> tokens. But results don't reflect above. Each cache entry has its own >>> lifespan. That's correct. But they are removed after the configured cache >>> timeout (individually based on their lifespan) even when they are kept >>> being used. That means the ACCESSED type expiry is not honored, I assume. >>> Is my understanding wrong? >>> >>> [1] >>> https://github.com/wso2/carbon-apimgt/blob/master/components/apimgt/org.wso2.carbon.apimgt.impl/src/main/java/org/wso2/carbon/apimgt/impl/utils/APIUtil.java#L7487 >>> >>> >>> p.s. what does setStoreByValue mean in [1]? >>> >>> Thanks, >>> Bhathiya >>> >>> >>>> >>>> 2. Cache eviction >>>> When cache capacity is reached and there is no more space to insert >>>> items, then 25% of the items are (forcefully) evicted (even if they have >>>> not expired). >>>> >>>> If the cache is periodically purged even ignoring the above two cases, >>>> then it is incorrect. Such code didn't exist in the early versions of >>>> caching that I implemented. >>>> >>>> Azeez >>>> >>>> On Fri, Jun 21, 2019 at 12:07 PM Nuwan Dias <nuw...@wso2.com> wrote: >>>> >>>>> Hi, >>>>> >>>>> I have heard about two mechanisms how the cache expires in WSO2 >>>>> products. >>>>> >>>>> 1. Each cache entry has its individual lifespan specified in the cache >>>>> timeout config (15m by default). >>>>> 2. A scheduled job that runs periodically (based on the cache timeout) >>>>> cleans the full cache on each run. This would mean that some cache entries >>>>> expire sooner than the others. >>>>> >>>>> Which of the above is correct? Or is it completely different? Can we >>>>> alter between the two based on a config? >>>>> >>>>> Thanks, >>>>> NuwanD. >>>>> >>>>> -- >>>>> *Nuwan Dias* | Director | WSO2 Inc. >>>>> (m) +94 777 775 729 | (e) nuw...@wso2.com >>>>> [image: Signature.jpg] >>>>> >>>> >>>> >>>> -- >>>> *Afkham Azeez* | Vice President | WSO2 Inc. >>>> (m) +94773320919 | (w) +94117435800 | (e) az...@wso2.com >>>> GET INTEGRATION AGILE >>>> Integration Agility for Digitally Driven Business >>>> >>>> >>> >>> -- >>> *Bhathiya Jayasekara* >>> *Technical Lead,* >>> *WSO2 inc., http://wso2.com <http://wso2.com>* >>> >>> *Phone: +94715478185* >>> *LinkedIn: http://www.linkedin.com/in/bhathiyaj >>> <http://www.linkedin.com/in/bhathiyaj>* >>> *Twitter: https://twitter.com/bhathiyax <https://twitter.com/bhathiyax>* >>> *Blog: http://movingaheadblog.blogspot.com >>> <http://movingaheadblog.blogspot.com/>* >>> >> > > -- > Ruwan Abeykoon | Director/Architect | WSO2 Inc. > (w) +947435800 | Email: ruw...@wso2.com > > -- *Bhathiya Jayasekara* *Technical Lead,* *WSO2 inc., http://wso2.com <http://wso2.com>* *Phone: +94715478185* *LinkedIn: http://www.linkedin.com/in/bhathiyaj <http://www.linkedin.com/in/bhathiyaj>* *Twitter: https://twitter.com/bhathiyax <https://twitter.com/bhathiyax>* *Blog: http://movingaheadblog.blogspot.com <http://movingaheadblog.blogspot.com/>*
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