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https://issues.apache.org/jira/browse/IGNITE-20327?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nikita Amelchev updated IGNITE-20327:
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Release Note: Fixed doubled serialization of CQ event oldValue field for
REMOVE/EXPIRY events.
> [Thin clients] Continuous Query EXPIRY/REMOVE events can consumes a huge
> amount of heap
> ----------------------------------------------------------------------------------------
>
> Key: IGNITE-20327
> URL: https://issues.apache.org/jira/browse/IGNITE-20327
> Project: Ignite
> Issue Type: Task
> Reporter: Mikhail Petrov
> Assignee: Mikhail Petrov
> Priority: Major
> Labels: ise
> Fix For: 2.16
>
> Time Spent: 1h 20m
> Remaining Estimate: 0h
>
> 1. CQ is registered through the thin client. Assume that we filter out all
> events except cache entry expired events.
> 2. A huge amount of cache entries expiry on the cluster and the corresponding
> CQ events are created on the node that holds CQ listener.
> 3. Assume that thin client connection is slow. Thus, all events designated
> for the thin client are accumulated in the selector queue
> GridSelectorNioSessionImpl#queue before they are sent. Note, that all thin
> clients messages stored in the serializes form.
> Here is two main problems
> 1. Currently EXPIRY and REMOVE CacheContinuousQueryEntry entries are
> initialized with both oldValue and newValue as a reference to the same object
> (that was done to meet JCache requirements - see
> https://issues.apache.org/jira/browse/IGNITE-8714)
> During thin client CQ event serialization, we process both oldValue and
> newValue independently. As a result, the same value is serialized twice,
> which can significantly increase the amount of memory consumed by the
> GridSelectorNioSessionImpl#queue.
> 2. Messages designated to the thin clients are serialized with the use of
> POOLED allocator. The problem here is that the POOLED allocator allocates
> memory in powers of two. As a result, if the serialized message is slightly
> larger than 2^n bytes, then twice as much memory will be allocated to store
> it.
> As a result each EXPIRY/REMOVE CQ event that is awaiting its sending to the
> thin client side can consume <expired/removed cache entry size> * 4 of Java
> Heap.
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