Shenjiaqi opened a new pull request, #20860:
URL: https://github.com/apache/flink/pull/20860
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## What is the purpose of the change
When protobuf serializer serializes an object, which is built directly with
builder without assign any value to field, the serializer will generate a zero
length byte[] and then write it into state with content '\0'（indicates zero
length data).
When recovered from checkpoint, protobuf seralizer deserialize the data. It
get length 0, and call InputStream#read(byte[] bytes, int offset, int count)
with count = 0.
The underlying Input implementation is
[NoFetchingInput](https://github.com/apache/flink/blob/9d2ae5572897f3e2d9089414261a250cfc2a2ab8/flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/NoFetchingInput.java).
It will call Inputsteam#read(byte[] bytes, int offset, int count) with count =
0.
The InputStream implementation is
[ByteStateHandleInputStream](https://github.com/apache/flink/blob/53d5e1cf9666517bc2fded60b510f2fd13d93f10/flink-runtime/src/main/java/org/apache/flink/runtime/state/memory/ByteStreamStateHandle.java#L140-L153)，It
will return -1 as long as no data left in memory, even if count is 0.
Any seralizer/deserializer with implementation like protobuf will encounter
problem like this (can not recovery from checkpoint with empty length
serialized value).
## Brief change log
Add check before return -1 in ByteStateHandleInputStream#read(byte[] bytes,
int offset, int count). If caller reads 0 bytes, it should always return 0
instead of -1.
## Verifying this change
This change added tests and can be verified as follows:
- Use a protobuf generated class as value in list state. Build object of
the class with builder and set no field. Try recovery from checkpoint. Before
this fix, recovery should fail.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (no)
- The serializers: (don't know)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
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