112 lines
7.1 KiB
Markdown
112 lines
7.1 KiB
Markdown
# Versioning
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Proto Socket tracks protocol compatibility separately from language package versions.
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## Current Versions
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- Protocol version: `0.1`
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- Dart package version: see `dart/pubspec.yaml`
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- Go module version: repository tag based
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`0.1` is the current compatibility contract for the checked-in available implementations. The wire format does not carry a protocol version field yet; compatibility is verified by shared proto definitions, unit tests, and cross-language tests.
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Protocol `0.1` also allows optional application-level convention messages for capability announcement and request error reporting. These conventions do not change the required handshake or the `PacketBase` wire fields unless they are promoted in a later protocol version.
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## Protocol Version
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The protocol version describes the wire-format and behavior contract that every language implementation must satisfy:
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- TCP uses a 4-byte big-endian payload length followed by one `PacketBase` protobuf payload.
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- WebSocket and WSS use one binary frame per `PacketBase` protobuf payload.
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- `PacketBase.typeName` routes the inner message by canonical protobuf full message name.
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- `nonce` increments for every outbound packet on a connection.
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- `responseNonce` links a response packet to the request nonce.
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- Heartbeat behavior follows `PROTOCOL.md`.
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Breaking protocol changes require a new major protocol version. Backward-compatible additions keep the same major protocol version but must include updated tests before release.
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## Proto Package and Wire Identity
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Proto package names are part of the wire identity because they prefix protobuf full message names. Package names must use lowercase snake_case segments joined by dots, for example `proto_socket` or `example_chat.v1`.
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The canonical package for the shared packet schema is `proto_socket`. Common message identities therefore use values such as `proto_socket.PacketBase`, `proto_socket.HeartBeat`, and `proto_socket.TestData`; `PacketBase.typeName` carries the inner message identity.
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Language-specific namespace options such as Go `go_package` or Java/Kotlin package names are package-generation details. They do not change the protocol package or wire `typeName`.
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## Git Release Standard
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Current consumption and release flow is Git ref/tag based. Package registry publication is optional future work, not the current release standard.
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Git releases must identify the repository ref/tag being consumed and use the full local validation matrix as the compatibility gate.
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## Package Version
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Each language implementation may publish on its own package cadence if registry releases are later introduced. Package versions communicate implementation releases, bug fixes, and language-specific API changes.
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A package release must state which protocol version it implements. A package version bump does not imply a protocol version bump unless the wire-format or required behavior changes.
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## Breaking Protocol Changes
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Examples of breaking protocol changes:
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- Renaming or removing `PacketBase` fields.
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- Changing the canonical proto package or `typeName` derivation without a compatibility path.
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- Changing `nonce` or `responseNonce` semantics.
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- Changing heartbeat request/response timing or echo behavior in a way that disconnects older peers.
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- Changing TCP framing, byte order, max packet handling, or WebSocket binary-frame rules.
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## Non-breaking Protocol Changes
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Examples of non-breaking changes:
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- Adding a new protobuf message type.
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- Adding optional fields to application messages when older peers can ignore them.
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- Adding a new language implementation that passes the existing protocol and cross-language tests.
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- Tightening tests or documentation without changing wire behavior.
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- Adding an optional hello/capability message that peers may ignore and that is not required before normal traffic.
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- Adding an optional standard error response convention, provided older peers can still fail by timeout or existing response type-mismatch behavior.
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Backward-compatible message additions require updated parser maps and cross-language tests before release.
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## Optional Capability Announcement
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`ProtoSocketHello`, or an equivalent project-specific message, is a candidate convention for announcing:
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- `protocolVersion`
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- stable `capabilities` tokens
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- optional implementation metadata
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In protocol `0.1`, this message is not a required handshake. A peer must be able to send and receive normal messages without first receiving a hello/capability message. Making a hello message mandatory, changing connection readiness semantics, or disconnecting older peers that do not send it requires a protocol-version review.
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## Standard Error Response Convention
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`ProtoSocketError`, or an equivalent project-specific message, is a candidate convention for request handler failures. A supported error response should carry the original request nonce in `responseNonce`, a stable error code, a safe message, and optional detail/debug fields.
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In protocol `0.1`, implementations may continue to report handler failure as timeout, response type mismatch, or implementation-specific errors. Requiring all handlers to emit a shared error response, or requiring every requester to treat a particular error message type specially, requires parser map updates, cross-language tests, and compatibility review.
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## nonce Overflow
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`nonce` and `responseNonce` fields are protobuf `int32` values (signed 32-bit).
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The maximum emitted nonce is `2,147,483,647` (`int32` max).
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Current policy:
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- Implementations start at `1` and increment by `1` on every send call, including requests and responses.
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- When selecting the next nonce to emit, implementations must skip any value that is currently used by an active pending request (`sendRequest` correlation map). This keeps nonce reuse from colliding with in-flight requests after wrap.
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- If all positive `int32` nonce values are currently pending, `sendRequest`/`send` must fail explicitly rather than emit a duplicate correlation nonce.
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- After issuing `2,147,483,647`, implementations reset the internal counter to `0`; the next emitted `PacketBase.nonce` is `1`.
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- `0` is reserved and must not be emitted as `PacketBase.nonce`, because `responseNonce == 0` means "not a response".
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Changing this wrap behavior or the reserved meaning of `responseNonce == 0` changes `nonce` semantics and requires compatibility review and cross-language boundary tests.
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## New Language Compatibility
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A new language implementation must target the current protocol version unless its README explicitly says otherwise. Before it is listed as available, it must:
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- Generate protobuf bindings from the canonical schema.
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- Use the same canonical protobuf full message name `typeName` values as the available implementations.
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- Keep language namespace/package options separate from the protobuf package used for wire identity.
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- Implement TCP, TLS+TCP, WS, and WSS framing consistently where the language runtime supports them.
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- Implement request-response correlation with `nonce` and `responseNonce`.
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- Handle heartbeat automatically inside the client/server core.
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- Pass same-language tests and cross-language tests against at least one available implementation.
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