heliang666s opened a new pull request, #15616:
URL: https://github.com/apache/dubbo/pull/15616
### Optimize Triple POJO Serialization with Zero-Copy
#### What is the purpose of this PR?
This PR introduces a significant **zero-copy optimization** for POJO
serialization within the Dubbo Triple protocol's wrapper mode. It targets UNARY
RPC calls to dramatically reduce memory allocation and improve performance.
#### Why is this change necessary?
Previously, serializing multiple POJO parameters involved creating an
intermediate `byte[]` for each parameter. This led to:
- High memory allocation and churn.
- Increased GC pressure, impacting overall application performance.
- Performance bottlenecks due to memory copy operations.
#### How did you implement it?
The core of this optimization is a **dual-phase streaming mechanism** for
**UNARY** RPC calls:
1. **Phase 1: Size Calculation (Allocation-Free)**
A lightweight `CountingOutputStream` calculates the serialized size of
each parameter *without* allocating memory.
2. **Phase 2: Direct Serialization**
The parameters are serialized directly to the network output stream,
prefixed with their calculated length.
To maintain backward compatibility, this new format is identified by
appending a `-streaming` suffix to the serialization type (e.g.,
`hessian4-streaming`). The server detects this suffix and uses a corresponding
streaming decoder.
The optimization automatically **falls back to the traditional method** for
streaming RPCs (SERVER_STREAM, BI_STREAM) and non-capable serializations,
ensuring no breaking changes.
#### What are the key benefits?
- **Reduced Memory Allocation:** Eliminates intermediate `byte[]` buffers
for parameters.
- **Lower GC Pressure:** Significantly fewer objects for the garbage
collector to manage.
- **Improved Performance:** Faster serialization/deserialization by avoiding
memory copies.
- **Full Backward Compatibility:** The new mechanism is interoperable with
older clients/servers and gracefully degrades when not applicable.
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