Protocol

requests and responses of rpcx use the same message format.

One message contains:

1. Header: 4 bytes
2. Message ID: 8 bytes
3. total size: 4 bytes, doesn't contain size of header and itself, uint32
4. size of servicePath: 4 bytes, uint32
5. servicePath: UTF-8 string
6. size of serviceMethod: 4 bytes, uint32
7. serviceMethod: UTF-8 string
8. size of metadata: 4 bytes, uint32
9. metadata: format: size key1 string size value1 string, can contains multipl e=key, value
10. size of playload: 4 bytes, uint32
11. playload: slice of byte

#4 + #6 + #8 + #10 + (4 + 4 + 4 + 4) must be equal to #3.

servicePath、serviceMethod、key and value in metadata must be UTF-8 string.

rpcx uses size of an element + element format to define one element. It is like TLVbut rpcx doesn't use Type because Type of those elements are UTF-8 string.

Use BigEndian for size (integer type, int64, uint32, etc.)

1、The first byte must be 0x08. It is a magic number.

2、The second byte is version. Current version is 0.

3、MessageType can be:
0: Request
1: Response

4、Heartbeat: bool. This message is heartbeat message or not

5、Oneway: bool. Need return response or not.

6、CompressType:
0: don't compress
1: Gzip

7、MessageStatusType: indicates response is an error or a normal response
0: Normal
1: Error

8、SerializeType
0: use raw bytes
1: JSON
2: Protobuf
3: MessagePack

If one service fails to handle requests, it can return an error. It sets MessageStatusType of response is 1 (ERROR) and sets the error message in metadata of the response. The key for the error is rpcx_error, and the value is error message.