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https://issues.apache.org/jira/browse/IGNITE-28942?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Anton Vinogradov updated IGNITE-28942:
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Labels: IEP-132 (was: )
> Evaluate replacing JdkMarshaller with binary in a self-contained mode
> ---------------------------------------------------------------------
>
> Key: IGNITE-28942
> URL: https://issues.apache.org/jira/browse/IGNITE-28942
> Project: Ignite
> Issue Type: Sub-task
> Components: messaging
> Reporter: Anton Vinogradov
> Assignee: Anton Vinogradov
> Priority: Major
> Labels: IEP-132
> Fix For: 2.19
>
>
> *Research task, finished. Result: keep {{JdkMarshaller}}. Kept for the record
> so the question does not come back.*
> h3. Question
> Can {{JdkMarshaller}} be dropped and binary used everywhere?
> h3. What was checked
> *Binary can be self-contained.* When a type is not registered, binary writes
> {{UNREGISTERED_TYPE_ID}} plus the class name
> ({{BinaryWriterExImpl#preWrite}}), and metadata can stay local
> ({{registerClassNameLocally}}, {{addMetaLocally}}). Thin client, JDBC and the
> standalone WAL reader already run binary with no cluster at all. So "binary
> needs discovery" is not true of the format.
> *But only with a full footer.* An object written by one context and read by a
> completely empty one:
> * {{compactFooter = false}}: read succeeds, cycles included, 84 bytes against
> 121 for jdk;
> * {{compactFooter = true}} (the default): read fails with "Cannot find
> metadata for object with compact footer", because the field layout comes from
> metadata that discovery distributes.
> {{compactFooter}} is a node-wide setting: {{BinaryWriterExImpl#postWrite}}
> reads {{ctx.isCompactFooter()}}. A per-call full-footer mode would have to be
> added.
> *The unregistered path is slow, and the reason is known.* 160 us against 24
> for a {{CacheConfiguration}}. {{BinaryContext#registerUserClassDescriptor}}
> stores the descriptor in {{descByCls}} only when registration succeeded;
> otherwise it returns the descriptor without caching it, so it is rebuilt by
> reflection on every call.
> *Pre-registration is not closed under nesting.* Marshalling a plain
> {{CacheConfiguration}} needs 9 types;
> {{javax.cache.configuration.FactoryBuilder$SingletonFactory}} and
> {{javax.cache.expiry.EternalExpiryPolicy}} are missing from
> {{META-INF/classnames.properties}}. {{failIfUnregistered = true}} does not
> help - it fires for internal types too.
> *On-disk formats would become a migration.* Cache configurations, metastore,
> snapshots and dumps are written with jdk and read by offline tools
> ({{DumpReader}} builds {{Marshallers.jdk()}} directly). Note that wire
> companions in such classes are {{transient}}, so today the two formats do not
> interfere - dropping jdk would end that.
> *And it would not even remove Java serialization.*
> {{BinaryUtils#isCustomJavaSerialization}} walks the whole hierarchy, so every
> {{Externalizable}} class and every class with {{writeObject}} goes to
> {{OptimizedMarshaller}} anyway. Three implementations would become two, not
> one.
> h3. Answer
> Keep {{JdkMarshaller}}. The move costs a new format mode, a descriptor-cache
> change, and a migration of data already written on user disks, and it buys
> one implementation less plus a few dozen bytes per object.
> This does not affect the rest of IGNITE-28935: it removes the *choice* of a
> marshaller, not a marshaller. If the picture changes later, only the call
> sites have to be revisited.
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