protocol_transport_core

Crate: protocol_transport_core · Path: crates/protocol_transport_core
Description (Cargo.toml): Universal transport foundation for multiple protocols - SpinKube optimized

Role

Universal transport foundation for A2A, MCP, Redpanda PubSub, and REST protocols. Protocol-agnostic, WASM-optimized, zero-copy design with composable transports. Provides the JSON-RPC 2.0 layer, streaming policies, header forwarding, and protocol routing that higher-level crates build on.

Feature flags

From crates/protocol_transport_core/Cargo.toml:

Feature	Purpose
`default`	Enables `client` and `server`
`client`	Client-side transport (`transport` module)
`server`	Server-side routing (`server` module)
`batch`	Batch request support

Public API (from `src/lib.rs`)

Modules: error, forward_headers, headers, jsonrpc, serialization, server (feature server), streaming, transport (feature client)

Core types:

UniversalRequest / UniversalResponse — protocol-agnostic request/response containers
ProtocolHandler trait — encode/decode between protocol-specific and universal formats
Transport trait — async send + health check (no Send bound for WASM compat)
AsyncProtocolHandler trait — Spin SDK async-compatible handler
ProtocolRouter — routes requests to registered protocol handlers
ProtocolHandlerFn — boxed function-based handler type

Re-exports:

ProtocolError, ProtocolResult, TransportError, TransportResult
ForwardedHeaders, sanitize_header_map, sanitize_headers
ProtocolHeaders
JsonRpcError, JsonRpcId, JsonRpcIncoming, JsonRpcNotification, JsonRpcRequest, JsonRpcResponse, JSONRPC_VERSION, error_codes
StreamingPolicy, RPC_REQUEST_TIMEOUT
IdleTimeoutStream (native only)

Example sketch

use protocol_transport_core::{ProtocolRouter, UniversalRequest, AsyncProtocolHandler};

let mut router = ProtocolRouter::new();
router.register("A2A", my_a2a_handler);
router.register("MCP", my_mcp_handler);

let request = UniversalRequest {
    method: "POST".into(),
    uri: "/jsonrpc".into(),
    headers: Default::default(),
    body: payload,
    protocol: "A2A".into(),
    correlation_id: uuid::Uuid::new_v4().to_string(),
};

let response = router.route_request(request)?;

Full API reference: cargo doc -p protocol_transport_core --no-deps