[jira] [Created] (FLINK-6025) User code ClassLoader not used when KryoSerializer fallbacks to serialization for copying

[Shang Yuanchun (Jira)]

Tzu-Li (Gordon) Tai created FLINK-6025:
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             Summary: User code ClassLoader not used when KryoSerializer fallbacks to serialization for copying
                 Key: FLINK-6025
                 URL: https://issues.apache.org/jira/browse/FLINK-6025
             Project: Flink
          Issue Type: Bug
          Components: Type Serialization System
            Reporter: Tzu-Li (Gordon) Tai


Reported in ML: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/AWS-exception-serialization-problem-td12063.html

This is a known Kryo issue with its {{JavaSerializer}}: https://github.com/EsotericSoftware/kryo/pull/483.

It happens when a {{Throwable}} is to be copied by the {{KryoSerialzer}}. Since we use the {{JavaSerializer}} for throwables, and {{JavaSerializer}} doesn't support copying, the {{KryoSerializer}} fallbacks to use de-/serialization for the throwable. The problem is that on deserialization, the classloader that the {{ObjectInputStream}} uses may be overriden, and doesn't specifically uses Kryo's configured classloader (i.e., the user code class loader), and results in {{ClassNotFoundException}}.

Generally, this may happen if the user also registers to use the {{JavaSerializer}} for their types.

To fix the problem for {{Throwable}} serializing in the {{KryoSerializer}}, we could either consider registering our own {{JavaSerializer}} that fixes this problem, or wait for the Kryo fix to be released (to be fixed in Kryo 4.0.1 release).



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