[ https://issues.apache.org/jira/browse/HTTPCLIENT-1165?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jon Moore updated HTTPCLIENT-1165: ---------------------------------- Issue Type: Improvement (was: Bug) @Manish: I've reclassified this as an improvement and not a bug, as the cache properly handles these race conditions if multiple responses have differing Date headers, so no semantic transparency is broken here--in other words no incorrect HTTP behavior is created by the cache. That said, request collapsing is a perfectly valid enhancement request--patches welcome. :) > Cache allows multipe requests to retrieve the same cacheable resource from > the server in multithreaded environment due to lack of proper locking > ------------------------------------------------------------------------------------------------------------------------------------------------ > > Key: HTTPCLIENT-1165 > URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1165 > Project: HttpComponents HttpClient > Issue Type: Improvement > Components: Cache > Affects Versions: Snapshot > Reporter: Manish Tripathi > > Consider the following scenario: > Two separate threads are launched at the same time with identical Http > requests through CachingHttpClient. > Both threads look up the same URI in the cache at [almost] the same time and > find no cached response for that URI. > Both threads fall back to backend HttpClient and make identical requests to > the server. > Both threads retrieve the resource and attempt to store it in the cache. > The same resource gets retrieved from the server twice and is stored in the > cache twice. > Obviously, the described algorithm is inefficient > Suggested fix: introduce read-write locking mechanism which would block > multiple requests to retrieve the same URI until one of the concurrent > requests has either received a response header indicating that the response > is not cacheable, or until cacheable response has been fully retrieved and > stored in the cache. The proposed pseudo-code follows: > cachingClient.execute(url) { > if (lock_count(url)>0) > lock=lockingFactory.acquireReadLock(url); > else > lock=lockingFactory.acquireWriteLock(url); > response=satisfyFromCache(url); > if (response==null) { > if (lock.isReadLock()) { lock.release(); > lock=lockingFactory.acquireWriteLock(url); } > response=satisfyFromServerAndStoreInCache(url); > } > lock.release(); > return response; > } > where lockingFactory instance is shared by multiple instances of > CachingHttpClient. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@hc.apache.org For additional commands, e-mail: dev-h...@hc.apache.org