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https://issues.apache.org/jira/browse/QPID-7728?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alex Rudyy closed QPID-7728.
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Resolution: Fixed
Fixed as part of QPID-7771
> [Java Broker] Existing implementation of fanout exchange is susceptible to
> memory leaks
> ---------------------------------------------------------------------------------------
>
> Key: QPID-7728
> URL: https://issues.apache.org/jira/browse/QPID-7728
> Project: Qpid
> Issue Type: Bug
> Components: Java Broker
> Affects Versions: qpid-java-broker-7.0.0
> Reporter: Alex Rudyy
>
> An implementation of fanout exchange {{FanoutExchangeImpl}} is susceptible to
> memory leaks. The scenarios when memory leaks can occur are described below.
> If binding does not have filter arguments, it is added into {{_queue}} and
> {{_unfilteredQueues }} (of {{FanoutExchangeImpl$BindingSet}}) (If binding is
> added multiple times, the counter in _queue is incremented)
> If binding has filter argument, it is added into {{_filteredQueues}} and
> {{_filteredBindings}} (of {{FanoutExchangeImpl$BindingSet}}).
> Thus, imagine the following scenario, when queue bindings are added to a
> fanout exchange:
> 1) add binding with filter and routing key set to null (binding is added
> into {{_filteredQueues}} and {{_filteredBindings}})
> 2) add binding with filter and routing key set to 'a' (binding is added into
> {{_filteredBindings}} ; {{_filteredQueue}} is not modified because queue is
> already there)
> 3) add binding without filter and routing key set to null (binding with null
> routing key is removed from {{_filteredBindings}} as part of
> {{Exchange#repaceBinding}} and added into {{_queues}} and
> {{_unfilteredQueue}} ({{_filteredQueues}} still has entry for a queue for
> routing key 'a'))
> 4) add binding without filter and routing key set to null again (binding
> with null routing key is removed from {{_unfilteredQueues}} and {{_queues
> }}as part of {{Exchange#repaceBinding}} but it is addeed into
> {{_filteredQueues}} second time (!!!) as {{_filteredBindings}} has binding
> for a routing key 'a'; it is re-added to {{_unfilteredQueues}} and
> {{_queues}} as part of {{Exchange#repaceBinding}}.
> 5) Repeating step 4 in a loop multiple times would result in adding into
> {{_filteredQueues}} a queue entry every time (line 203) which might
> eventually result in OOM.
> Here is a second scenario when leak is possible
> 1) add binding with filter and routing key set to 'a' (binding is added into
> {{_filteredQueues}} and {{_filteredBindings}})
> 1) add binding without filter and routing key set to null (added into
> {{_queues}} and {{_unfilteredQueues}}. The queue is present in
> {{_filteredQueues}} and {{_filteredBindings}} due to step 1)
> 2) add binding with filter and routing key set to 'b' (binding is added into
> {{_filteredQueues}} second time as it is present in {{_unfilteredQueues}});
> binding is added into {{_filteredBindings}}
> 3) Repeating step 2 in a loop multiple times would result in adding into
> {{_filteredQueues}} a queue entry every time (line 91) which might eventually
> result in OOM.
> I think that implementation of {{FanoutExchangeImpl$BindingSet}} does not
> really need {{_filteredQueues}} and {{_unfilteredQueues}}. These fields look
> redundant to me.
> Map {{_queues}} already containa unfiltered queues, thus
> {{_unfilteredQueues.contains}} can be replaced with call to
> {{_queues.containsKey}}.
> Map {{_filteredBindings}} contains filtered queues, thus
> {{_filteredQueues.contains}} can be replaced with call to
> {{_filteredBindings.containsKey}}.
> I think that {{_filteredBindings}} can be simplified and replaced with
> {{Map<MessageDestination, FilterManager> _filteredBindings}}. Every new
> filter can be added into {{FilterManage}}r using
> {{FilterManager#addFilter(String name,MessageFilter filter)}} similar to
> {{DirectExchangeImp}} where we can pass binding key as a name .
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