weiqingy opened a new pull request, #871:
URL: https://github.com/apache/flink-agents/pull/871
Linked issue: #865
### Purpose of change
`ActionStateSerde` serializes `MemoryUpdate.value` (declared `Object`) via a
plain, type-info-less Jackson `ObjectMapper`, so a `byte[]` is written as a
base64 `String` and — with no type tag — deserialized back as `String` on
crash/replay, silently writing the wrong type into memory.
This is a pre-existing, Java-native defect: a Java agent can `set` a
`byte[]` memory value directly, so the bug predates admitting Python `bytes`
into the memory contract (#846); #846 only makes it more likely to be hit.
The fix adds a targeted, field-scoped envelope (de)serializer bound to
`MemoryUpdate.value` via a Jackson mixin. A `byte[]` is written as
`{"__flink_agents_bytes__":"<base64>"}` and reversed back to `byte[]` on read;
every other value type delegates to Jackson's stock untyped-`Object`
(de)serialization and stays byte-identical on disk, so in-flight durable state
remains replay-compatible.
The (de)serializer is bound per-property (mixin on `value`), not registered
globally on `byte[]`, so `CallResult`'s statically-typed `byte[]` fields are
untouched. The envelope carries only base64 text → `byte[]`, so it adds no
polymorphic-typing deserialization surface.
Scope: only a top-level `byte[]` value is preserved. A `byte[]` nested
inside a `List`/`Map` value goes through the default serializers and is out of
scope, documented in the code.
### Tests
Added round-trip regressions in `ActionStateSerdeTest` (the first mirrors
the issue repro exactly):
- `byte[]` on a short-term memory update round-trips as `byte[]` (issue
repro; `assertArrayEquals`)
- `byte[]` on a sensory memory update
- empty `byte[0]`
- a `String` value still round-trips as `String` (envelope doesn't disturb
the common case)
- a `Map` value still round-trips as a `Map` (not misread as an envelope;
on-disk shape unchanged)
- reserved-key residual: a user `Map` that is exactly
`{"__flink_agents_bytes__":"<base64>"}` recovers as `byte[]` (documented
residual), while any second key keeps it a `Map`
`mvn test -Dtest=ActionStateSerdeTest -pl runtime` → 16 tests, 0 failures.
`mvn test -pl runtime` → 396 tests, 0 failures.
### API
No public API change. `MemoryUpdate`, `ActionState`, and
`ActionStateSerde.serialize/deserialize` signatures are unchanged; only the
on-disk encoding of a `byte[]` value changes (it was previously broken).
### Documentation
- [ ] `doc-needed`
- [x] `doc-not-needed`
- [ ] `doc-included`
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