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feat(java): type meta encoding for java (#1556)
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## What does this PR do?

This PR implements type meta encoding for java proposed in #1240 .

The type meta encoding in xlang spec proposed in #1413 will be finished
in another PR based on this PR.

The spec has been updated too:

type meta header
```
|      8 bytes meta header      | meta size |   variable bytes   |  variable bytes   | variable bytes |
+-------------------------------+-----------|--------------------+-------------------+----------------+
| 7 bytes hash + 1 bytes header | 1~2 bytes | current class meta | parent class meta |      ...       |
```

And the encoding for packge/class/field name has been updated to:
```
- Package name encoding(omitted when class is registered):
    - encoding algorithm: `UTF8/ALL_TO_LOWER_SPECIAL/LOWER_UPPER_DIGIT_SPECIAL`
    - Header: `6 bits size | 2 bits encoding flags`. The `6 bits size: 0~63`  will be used to indicate size `0~62`,
      the value `63` the size need more byte to read, the encoding will encode `size - 62` as a varint next.
- Class name encoding(omitted when class is registered):
    - encoding algorithm: `UTF8/LOWER_UPPER_DIGIT_SPECIAL/FIRST_TO_LOWER_SPECIAL/ALL_TO_LOWER_SPECIAL`
    - header: `6 bits size | 2 bits encoding flags`. The `6 bits size: 0~63`  will be used to indicate size `1~64`,
      the value `63` the size need more byte to read, the encoding will encode `size - 63` as a varint next.
- Field info:
    - header(8
      bits): `3 bits size + 2 bits field name encoding + polymorphism flag + nullability flag + ref tracking flag`.
      Users can use annotation to provide those info.
        - 2 bits field name encoding:
            - encoding: `UTF8/ALL_TO_LOWER_SPECIAL/LOWER_UPPER_DIGIT_SPECIAL/TAG_ID`
            - If tag id is used, i.e. field name is written by an unsigned varint tag id. 2 bits encoding will be `11`.
        - size of field name:
            - The `3 bits size: 0~7`  will be used to indicate length `1~7`, the value `6` the size read more bytes,
              the encoding will encode `size - 7` as a varint next.
            - If encoding is `TAG_ID`, then num_bytes of field name will be used to store tag id.
    - Field name: If type id is set, type id will be used instead. Otherwise meta string encoding length and data will
      be written instead.
```

## Meta size
Before this PR:
```java
class org.apache.fury.benchmark.data.MediaContent 78
class org.apache.fury.benchmark.data.Media 208
class org.apache.fury.benchmark.data.Image 114
```

With this PR:
```java
class org.apache.fury.benchmark.data.MediaContent 53
class org.apache.fury.benchmark.data.Media 114
class org.apache.fury.benchmark.data.Image 68
```

The size of class meta reduced by half, which is a great gain.

The size can be reduded more if we introduce field name hash, but it's
not related to this PR. We can discuss it in another PR.

## Related issues

#1240 
#203 
#202 


## Does this PR introduce any user-facing change?

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describing the need to do so and update the document if necessary.
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- [ ] Does this PR introduce any public API change?
- [ ] Does this PR introduce any binary protocol compatibility change?


## Benchmark

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chaokunyang committed May 2, 2024
1 parent f218c91 commit 63bbe45
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51 changes: 28 additions & 23 deletions docs/specification/java_serialization_spec.md
Original file line number Diff line number Diff line change
Expand Up @@ -112,9 +112,9 @@ For Schema consistent mode, class will be encoded as an enumerated string by ful
the meta layout for schema evolution mode:

```
| 8 bytes meta header | variable bytes | variable bytes | variable bytes |
+-------------------------------+--------------------+-------------------+----------------+
| 7 bytes hash + 1 bytes header | current class meta | parent class meta | ... |
| 8 bytes meta header | meta size | variable bytes | variable bytes | variable bytes |
+-------------------------------+-----------|--------------------+-------------------+----------------+
| 7 bytes hash + 1 bytes header | 1~2 bytes | current class meta | parent class meta | ... |
```

Class meta are encoded from parent class to leaf class, only class with serializable fields will be encoded.
Expand All @@ -128,8 +128,14 @@ Meta header is a 64 bits number value encoded in little endian order.
class doesn't have fields to serialize, or we're in a context which serialize fields of current class
only( `ObjectStreamSerializer#SlotInfo` is an example), num classes will be 1.
- 5rd bit is used to indicate whether this class needs schema evolution.
- 6rd bit is used to indicate whether the size sum of all layers meta is less than 256.
- Other 56 bits is used to store the unique hash of `flags + all layers class meta`.

### Meta size

- If the size sum of all layers meta is less than 256, then one byte is written next to indicate the length of meta.
- Otherwise, write size as two bytes in little endian.

### Single layer class meta

```
Expand All @@ -150,34 +156,33 @@ Meta header is a 64 bits number value encoded in little endian order.
fields info of those fields which aren't annotated by tag id for deserializing schema consistent fields, then use
fields info in meta for deserializing compatible fields.
- Package name encoding(omitted when class is registered):
- Header:
- If meta string encoding is `LOWER_SPECIAL` and the length of encoded string `<=` 128, then header will be
`7 bits size + flag(set)`.
Otherwise, header will be `4 bits unset + 3 bits encoding flags + flag(unset)`
- Package name:
- If bit flag is set, then package name will be encoded meta string binary.
- Otherwise, it will be `| unsigned varint length | encoded meta string binary |`
- Class name encoding(omitted when class is registered)::
- header:
- If meta string encoding is in `LOWER_SPECIAL~LOWER_UPPER_DIGIT_SPECIAL (0~3)`, and the length of encoded
string `<=` 32, then the header will be `5 bits size + 2 bits encoding flags + flag(set)`.
- Otherwise, header will be `| unsigned varint length | encoded meta string binary |`
- encoding algorithm: `UTF8/ALL_TO_LOWER_SPECIAL/LOWER_UPPER_DIGIT_SPECIAL`
- Header: `6 bits size | 2 bits encoding flags`. The `6 bits size: 0~63` will be used to indicate size `0~62`,
the value `63` the size need more byte to read, the encoding will encode `size - 62` as a varint next.
- Class name encoding(omitted when class is registered):
- encoding algorithm: `UTF8/LOWER_UPPER_DIGIT_SPECIAL/FIRST_TO_LOWER_SPECIAL/ALL_TO_LOWER_SPECIAL`
- header: `6 bits size | 2 bits encoding flags`. The `6 bits size: 0~63` will be used to indicate size `1~64`,
the value `63` the size need more byte to read, the encoding will encode `size - 63` as a varint next.
- Field info:
- header(8
bits): `reserved 1 bit + 3 bits field name encoding + polymorphism flag + nullability flag + ref tracking flag + tag id flag`.
bits): `3 bits size + 2 bits field name encoding + polymorphism flag + nullability flag + ref tracking flag`.
Users can use annotation to provide those info.
- tag id: when set to 1, field name will be written by an unsigned varint tag id.
- ref tracking: when set to 0, ref tracking will be disabled for this field.
- nullability: when set to 0, this field won't be null.
- 2 bits field name encoding:
- encoding: `UTF8/ALL_TO_LOWER_SPECIAL/LOWER_UPPER_DIGIT_SPECIAL/TAG_ID`
- If tag id is used, i.e. field name is written by an unsigned varint tag id. 2 bits encoding will be `11`.
- size of field name:
- The `3 bits size: 0~7` will be used to indicate length `1~7`, the value `6` the size read more bytes,
the encoding will encode `size - 7` as a varint next.
- If encoding is `TAG_ID`, then num_bytes of field name will be used to store tag id.
- ref tracking: when set to 1, ref tracking will be enabled for this field.
- nullability: when set to 1, this field can be null.
- polymorphism: when set to 1, the actual type of field will be the declared field type even the type if
not `final`.
- 3 bits field name encoding will be set to meta string encoding flags when tag id is not set.
- type id:
- For registered type-consistent classes, it will be the registered class id.
- Otherwise it will be encoded as `OBJECT_ID` if it isn't `final` and `FINAL_OBJECT_ID` if it's `final`. The
meta
for such types is written separately instead of inlining here is to reduce meta space cost if object of this
type is serialized in current object graph multiple times, and the field value may be null too.
meta for such types is written separately instead of inlining here is to reduce meta space cost if object of
this type is serialized in current object graph multiple times, and the field value may be null too.
- Field name: If type id is set, type id will be used instead. Otherwise meta string encoding length and data will
be written instead.

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,11 @@ public MetaSharedCodecBuilder(TypeRef<?> beanType, Fury fury, ClassDef classDef)
f -> MetaSharedSerializer.consolidateFields(f.getClassResolver(), beanClass, classDef));
DescriptorGrouper grouper =
DescriptorGrouper.createDescriptorGrouper(
descriptors, true, fury.compressInt(), fury.compressLong());
fury.getClassResolver()::isMonomorphic,
descriptors,
false,
fury.compressInt(),
fury.compressLong());
objectCodecOptimizer =
new ObjectCodecOptimizer(beanClass, grouper, !fury.isBasicTypesRefIgnored(), ctx);
}
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@
import org.apache.fury.codegen.Expression.StaticInvoke;
import org.apache.fury.codegen.ExpressionVisitor;
import org.apache.fury.memory.Platform;
import org.apache.fury.meta.ClassDef;
import org.apache.fury.reflect.TypeRef;
import org.apache.fury.serializer.ObjectSerializer;
import org.apache.fury.serializer.PrimitiveSerializers.LongSerializer;
Expand Down Expand Up @@ -87,13 +88,23 @@ public class ObjectCodecBuilder extends BaseObjectCodecBuilder {

public ObjectCodecBuilder(Class<?> beanClass, Fury fury) {
super(TypeRef.of(beanClass), fury, Generated.GeneratedObjectSerializer.class);
Collection<Descriptor> descriptors =
classResolver.getAllDescriptorsMap(beanClass, true).values();
Collection<Descriptor> descriptors;
boolean shareMeta = fury.getConfig().shareMetaContext();
if (shareMeta) {
ClassDef classDef = classResolver.getClassDef(beanClass, true);
descriptors = classDef.getDescriptors(classResolver, beanClass);
} else {
descriptors = fury.getClassResolver().getAllDescriptorsMap(beanClass, true).values();
}
classVersionHash =
new Literal(ObjectSerializer.computeVersionHash(descriptors), PRIMITIVE_INT_TYPE);
DescriptorGrouper grouper =
DescriptorGrouper.createDescriptorGrouper(
descriptors, false, fury.compressInt(), fury.compressLong());
fury.getClassResolver()::isMonomorphic,
descriptors,
false,
fury.compressInt(),
fury.compressLong());
objectCodecOptimizer =
new ObjectCodecOptimizer(beanClass, grouper, !fury.isBasicTypesRefIgnored(), ctx);
if (isRecord) {
Expand Down
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