Kenneth Knowles created BEAM-169:
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Summary: Need serialized form and serialVersionUID for user-facing
superclasses
Key: BEAM-169
URL: https://issues.apache.org/jira/browse/BEAM-169
Project: Beam
Issue Type: Bug
Components: sdk-java-core
Reporter: Kenneth Knowles
When a class does not have an explicit {{serialVersionUID}}, it should be
considered an unstable value based on the exact version of the code. This is
fine for transmission most of the time, but never acceptable for persistence
where backwards compatibility matters.
There are two use cases that require explicit serialized form and
{{serialVersionUID}} even just for transmission. They are required for
user-facing superclasses such as DoFn, WindowFn, etc, to support the following:
# Encoding a pipeline with a JDK and decoding with a JDK that computes defaults
differently.
# Encoding a pipeline against a version of the Beam SDK and decoding with a
different version.
The first situation should be rare since there is a deterministic spec, but we
have unfortunately seen it.
The second situation is very reasonable; a runner might want to run with
additional security fixes in the SDK, etc. Given a correct semantic version for
the SDK, the pipeline author and runner author may reasonably expect it to work.
So we should add explicit serialization to superclasses that are necessarily
encoded as part of a user's pipeline.
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