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https://issues.apache.org/jira/browse/DIRMINA-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13048696#comment-13048696
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Platon Potapov commented on DIRMINA-838:
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AttributeKeys do get discarded; MINA leaks no memory. But our project creates a
lot of connections (thousands per second), so the overhead of
creating/discarding many AttributeKeys is tangible. In case AttributeKeys do
not need to be unique per ProtocolCodecFilter, this hurts performance for no
benefit.
However, I am not familiar with MINA well enough to assert that AttributeKeys
can by design be singletons in this place - can they?
You said there were failures with having these being static - could it have
been because AttributeKeys were being incorrectly used elsewhere (a latent bug)?
> Redundant AttributeKey allocation resulting in high garbage collector
> activity
> -------------------------------------------------------------------------------
>
> Key: DIRMINA-838
> URL: https://issues.apache.org/jira/browse/DIRMINA-838
> Project: MINA
> Issue Type: Improvement
> Components: Filter
> Affects Versions: 2.0.3
> Environment: java version "1.6.0_22"
> Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
> Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)
> Reporter: Platon Potapov
>
> The classes CumulativeProtocolDecoder and ProtocolCodecFilter (there are
> others too, but these two are the important ones for our project) have
> members of type AttributeKey declared as:
> private final AttributeKey ENCODER = new
> AttributeKey(ProtocolCodecFilter.class, "encoder");
> As can be seen, these are not static, so each time ProtocolCodecFilter is
> created, AttributeKey objects get created as well, which in turn involves
> creation of a lot of String and char[] objects. jProfiler indicates that
> AttributeKey is accountable for creation of about 85% of all Strings and
> char[] in runs of our project, so it makes a significant difference for us.
> Is it OK for these attribute key objects to be singletons? If not, what would
> take to make them singletons?
> Some of other MINA filters have AttributeKeys as static members (e.g.
> MdcInjectionFilter, SslFilter).
> To summarize: the improvement being requested is to make the pre-defined
> AttributeKey objects static within classes such as CumulativeProtocolDecoder
> and ProtocolCodecFilter.
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