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Posted to dev@hc.apache.org by "Nikola Petrov (JIRA)" <ji...@apache.org> on 2013/09/02 18:08:51 UTC

[jira] [Updated] (HTTPCLIENT-1395) Call the storage implementation only once on a cache miss

     [ https://issues.apache.org/jira/browse/HTTPCLIENT-1395?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nikola Petrov updated HTTPCLIENT-1395:
--------------------------------------

    Attachment: call-storage-implementation-once.patch

The patch that makes sure the storage backend is called only once on a cache miss
                
> Call the storage implementation only once on a cache miss
> ---------------------------------------------------------
>
>                 Key: HTTPCLIENT-1395
>                 URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1395
>             Project: HttpComponents HttpClient
>          Issue Type: Improvement
>          Components: HttpCache
>    Affects Versions: 4.2.5
>            Reporter: Nikola Petrov
>            Priority: Minor
>         Attachments: call-storage-implementation-once.patch
>
>
> I am trying to use the httpclient-cache component with a Cassandra backend. Everything seems good except that HttpCacheStorage#getEntry is getting called 3 times the first time resulting in a performance bottleneck. There might be a way to handle this in the Storage implementation by caching the recently queried values but I think that a better place is in the CachingHttpClient class. The current code expects zero latency to the storage backend(the current implementations are all memory based) but here is a patch that fixes the problem. Some notes:
> * I am using the code from the 4.2.5 release(but can port the code to the current trunk) 
> * test is provided in org.apache.http.impl.client.cache.TestCachingHttpClient
> * BasicHttpCache is patched to expose methods that check if the key is found or if a proper variant is found - without this there is no way to say if there was a real cache miss or the specific variant is missing
> * CachingHttpClient is checking if the current HttpCache implementation is BasicHttpCache so it can use the new methods - I didn't want to change the interface because this will add breaking changes to the API

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