Vincent Herlemont
201 lines
8.5 KiB
Markdown
201 lines
8.5 KiB
Markdown
# Native model
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[](https://crates.io/crates/native_model)
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[](https://github.com/vincent-herlemont/native_model/actions/workflows/build_and_test_release.yml)
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[](https://docs.rs/native_model)
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[](LICENSE)
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A thin wrapper around serialized data which add information of identity and version.
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See [concepts](#concepts) for more details.
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## Goals
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- **Interoperability**: Allows different applications to work together, even if they are using different
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versions of the data model.
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- **Data Consistency**: Ensure that we process the data expected model.
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- **Flexibility**: You can use any serialization format you want. More details [here](#setup-your-serialization-format).
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- **Performance**: A minimal overhead (encode: ~20 ns, decode: ~40 ps). More details [here](#performance).
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## Usage
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```
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Application 1 (DotV1) Application 2 (DotV1 and DotV2)
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Encode DotV1 |----------------------------------------> | Decode DotV1 to DotV2
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| | Modify DotV2
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Decode DotV1 | <----------------------------------------| Encode DotV2 back to DotV1
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```
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```rust,skt-main
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// Application 1
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let dot = DotV1(1, 2);
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let bytes = native_model::encode(&dot).unwrap();
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// Application 1 sends bytes to Application 2.
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// Application 2
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// We are able to decode the bytes directly into a new type DotV2 (upgrade).
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let (mut dot, source_version) = native_model::decode::<DotV2>(bytes).unwrap();
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assert_eq!(dot, DotV2 {
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name: "".to_string(),
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x: 1,
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y: 2
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});
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dot.name = "Dot".to_string();
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dot.x = 5;
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// For interoperability, we encode the data with the version compatible with Application 1 (downgrade).
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let bytes = native_model::encode_downgrade(dot, source_version).unwrap();
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// Application 2 sends bytes to Application 1.
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// Application 1
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let (dot, _) = native_model::decode::<DotV1>(bytes).unwrap();
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assert_eq!(dot, DotV1(5, 2));
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```
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Full example [here](./tests/example/example_main.rs).
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When to use it?
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- Your applications that interact with each other are written in Rust.
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- Your applications evolve independently need to read serialized data coming from each other.
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- Your applications store data locally and need to read it later by a newer version of the application.
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- Your systems need to be upgraded incrementally. Instead of having to upgrade the entire system at once, individual
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applications can be upgraded one at a time, while still being able to communicate with each other.
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When not to use it?
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- Your applications that interact with each other are **not all** written in Rust.
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- Your applications need to communicate with other systems that you don't control.
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- You need to have a human-readable format. (You can use a human-readable format like JSON wrapped in a native model,
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but you have to unwrap it to see the data correctly.)
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## Status
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Early development. Not ready for production.
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## Concepts
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In order to understand how the native model works, you need to understand the following concepts.
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- **Identity**(`id`): The identity is the unique identifier of the model. It is used to identify the model and
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prevent to decode a model into the wrong Rust type.
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- **Version**(`version`) The version is the version of the model. It is used to check the compatibility between two
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models.
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- **Encode**: The encode is the process of converting a model into a byte array.
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- **Decode**: The decode is the process of converting a byte array into a model.
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- **Downgrade**: The downgrade is the process of converting a model into a previous version of the model.
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- **Upgrade**: The upgrade is the process of converting a model into a newer version of the model.
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Under the hood, the native model is a thin wrapper around serialized data. The `id` and the `version` are twice encoded with a [`little_endian::U32`](https://docs.rs/zerocopy/latest/zerocopy/byteorder/little_endian/type.U32.html). That represents 8 bytes, that are added at the beginning of the data.
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```
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+------------------+------------------+------------------------------------+
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| ID (4 bytes) | Version (4 bytes)| Data (indeterminate-length bytes) |
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+------------------+------------------+------------------------------------+
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```
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## Setup your serialization format
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First, you need to set up your serialization format. You can use any serialization format.
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Just define a struct with the name you want. This struct must implement [`native_model::Encode`](https://docs.rs/native_model/latest/native_model/trait.Encode.html) and [`native_model::Decode`](https://docs.rs/native_model/latest/native_model/trait.Decode.html) traits.
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In the below example we have created a struct `Bincode` that use the [bincode](https://docs.rs/bincode/latest/bincode/) crate:
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```rust,skt-define-serilization-format
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pub struct Bincode;
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impl<T: bincode::Encode> native_model::Encode<T> for Bincode {
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type Error = bincode::error::EncodeError;
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fn encode(obj: &T) -> Result<Vec<u8>, bincode::error::EncodeError> {
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bincode::encode_to_vec(obj, bincode::config::standard())
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}
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}
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impl<T: bincode::Decode> native_model::Decode<T> for Bincode {
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type Error = bincode::error::DecodeError;
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fn decode(data: Vec<u8>) -> Result<T, bincode::error::DecodeError> {
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bincode::decode_from_slice(&data, bincode::config::standard()).map(|(result, _)| result)
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}
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}
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```
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Full examples:
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- [bincode with encode/decode](./tests/example/encode_decode/bincode.rs)
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- [bincode with serde](./tests/example/encode_decode/bincode_serde.rs)
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## Setup your data model
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Define your model using the macro [`native_model`](file:///home/vincentherlemont/IdeaProjects/native_model/target/doc/native_model/attr.native_model.html).
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Attributes:
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- `id = u32`: The unique identifier of the model.
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- `version = u32`: The version of the model.
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- `with = type`: The serialization format that you use for the Encode/Decode implementation. Setup [here](#setup-your-serialization-format).
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- `from = type`: Optional, the previous version of the model.
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- `type`: The previous version of the model that you use for the From implementation.
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- `try_from = (type, error)`: Optional, the previous version of the model with error handling.
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- `type`: The previous version of the model that you use for the TryFrom implementation.
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- `error`: The error type that you use for the TryFrom implementation.
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```rust,skt-define-models
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use native_model::native_model;
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#[derive(Encode, Decode, PartialEq, Debug)]
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#[native_model(id = 1, version = 1, with = Bincode)]
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struct DotV1(u32, u32);
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#[derive(Encode, Decode, PartialEq, Debug)]
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#[native_model(id = 1, version = 2, with = Bincode, from = DotV1)]
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struct DotV2 {
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name: String,
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x: u64,
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y: u64,
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}
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// Implement the conversion between versions From<DotV1> for DotV2 and From<DotV2> for DotV1.
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#[derive(Encode, Decode, PartialEq, Debug)]
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#[native_model(id = 1, version = 3, with = Bincode, try_from = (DotV2, anyhow::Error))]
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struct DotV3 {
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name: String,
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cord: Cord,
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}
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#[derive(Encode, Decode, PartialEq, Debug)]
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struct Cord {
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x: u64,
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y: u64,
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}
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// Implement the conversion between versions From<DotV2> for DotV3 and From<DotV3> for DotV2.
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```
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Full example [here](tests/example/example_define_model.rs).
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## Performance
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Native model has
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been designed to have a minimal and constant overhead. That means that the overhead is the same
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whatever the size of the data. Under the wood we use the [zerocopy](https://docs.rs/zerocopy/latest/zerocopy/) crate
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to avoid unnecessary copies.
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👉 To know the total time of the encode/decode, you need to add the time of your serialization format.
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Resume:
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- **Encode**: ~20 ns
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- **Decode**: ~40 ps
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| data size | encode time (ns) | decode time (ps) |
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|:--------------------:|:---------------------:|:-----------------------:|
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| 1 B | 19.769 ns - 20.154 ns | 40.526 ps - 40.617 ps |
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| 1 KiB | 19.597 ns - 19.971 ns | 40.534 ps - 40.633 ps |
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| 1 MiB | 19.662 ns - 19.910 ns | 40.508 ps - 40.632 ps |
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| 10 MiB | 19.591 ns - 19.980 ns | 40.504 ps - 40.605 ps |
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| 100 MiB | 19.669 ns - 19.867 ns | 40.520 ps - 40.644 ps |
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Benchmark of the native model overhead [here](benches/overhead.rs).
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