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Date: Sat, 12 Nov 2005 01:04:03 +0100 (CET)
From: "Stephane Bailliez (JIRA)" <directory-dev@incubator.apache.org>
To: dev@directory.apache.org
Subject: [jira] Commented: (DIRLDAP-71) CachingNormalizer exhibits concurrency
 flaw under load.
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    [ http://issues.apache.org/jira/browse/DIRLDAP-71?page=comments#action_12357459 ] 

Stephane Bailliez commented on DIRLDAP-71:
------------------------------------------

I might be missing something but there's no need to me to do a containsKey() call.
AFAIK you'll never get a null normalized value stored in the cache plus the containsKey() is pretty inefficient as it is iterating over all keys to find if it exists so you'll want to avoid that call.

The Normalizer interface should certainly be documented to make it clear that it does not accept null values to be normalized and that it should not return null.

> CachingNormalizer exhibits concurrency flaw under load.
> -------------------------------------------------------
>
>          Key: DIRLDAP-71
>          URL: http://issues.apache.org/jira/browse/DIRLDAP-71
>      Project: Directory LDAP
>         Type: Bug
>   Components: Common
>     Versions: 0.9.3
>     Reporter: Jacob S. Barrett
>  Attachments: CachingNormalizer-Concurrency.patch
>
> CachingNormalizer doesn't have it's cache protected from concurrent modifications.  Under load a state is reached where cache.containsKey(key) is true but the result of cache.get(key) results in an unexpected null value and thus a NullPointerException.  This is really only reached when you have more than threads than the max cache size and therefore items in the cache are being purged.  The attached path synchronizes the cache.  It would be better to use a R/W lock from JSR 166 backport or something similar.

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