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https://issues.apache.org/jira/browse/NUTCH-471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12491313
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Enis Soztutar commented on NUTCH-471:
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> Nice trick with the unsynchronized check. :)
Wow, indeed i have used a pattern w/o knowing about it :) Seemed a simple and
efficient solution to me.
>Isn't the DCL declared to be broken?
After reading http://en.wikipedia.org/wiki/Double-checked_locking, i can say
that this a very subtle bug. As suggested we can fix it by declaring NutchBean
volatile. However i guess, that in that case would the servlet container should
also be configured to use Java 1.5 instead of 1.4.
> Fix synchronization in NutchBean creation
> -----------------------------------------
>
> Key: NUTCH-471
> URL: https://issues.apache.org/jira/browse/NUTCH-471
> Project: Nutch
> Issue Type: Bug
> Components: searcher
> Affects Versions: 1.0.0
> Reporter: Enis Soztutar
> Fix For: 1.0.0
>
> Attachments: NutchBeanCreationSync_v1.patch
>
>
> NutchBean is created and then cached in servlet context. But
> NutchBean.get(ServletContext app, Configuration conf) is not syncronized,
> which causes more than one instance of the bean (and
> DistributedSearch$Client) if servlet container is accessed rapidly during
> startup.
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