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https://issues.apache.org/jira/browse/IGNITE-4157?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15687126#comment-15687126
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Sergey Chugunov commented on IGNITE-4157:
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Implemented requesting of mapping by client when it doesn't have a mapping in
local cache it needs to unmarshal some data.
This may happen because discovery events are sent to clients asynchronously so
it is possible that servers already accepted new mapping but clients aren't
aware of it.
> Use discovery custom messages instead of marshaller and system cache
> --------------------------------------------------------------------
>
> Key: IGNITE-4157
> URL: https://issues.apache.org/jira/browse/IGNITE-4157
> Project: Ignite
> Issue Type: Improvement
> Components: cache
> Reporter: Alexey Goncharuk
> Assignee: Sergey Chugunov
> Fix For: 2.0
>
>
> Currently we use system caches for keeping classname to class ID mapping and
> for storing binary metadata
> This has several serious disadvantages:
> 1) We need to introduce at least two additional thread pools for each of
> these caches
> 2) Since cache operations require stable topology, registering a class ID or
> updating metadata inside a transaction or another cache operation is tricky
> and deadlock-prone.
> 3) It may be beneficial in some cases to have nodes with no caches at all,
> currently this is impossible because system caches are always present.
> 4) Reading binary metadata leads to huge local contention, caching metadata
> values in a local map doubles memory consumption
> I suggest we use discovery custom events for these purposes. Each node will
> have a corresponding local map (state) which will be updated inside custom
> event handler. From the first point of view, this should remove all the
> disadvantages above.
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