repe-rs

Rust implementation of the REPE RPC protocol with JSON and BEVE body support.

• Spec reference: https://github.com/repe-org/REPE
• Crate: repe on crates.io

This crate provides:

• REPE header and message types with correct little-endian encoding
• Message encode/decode to/from bytes and I/O helpers for streams
• JSON body helpers using serde/serde_json
• BEVE binary body helpers via the beve crate
• Dynamic registry routing with JSON Pointer semantics
• Error codes and formats aligned with the spec

Installation

Add to your Cargo.toml:

[dependencies]
repe = "0.1"

Tip: run cargo add repe to automatically pull the latest compatible release.

Quick start

use repe::{Message, QueryFormat, BodyFormat};

// Build a JSON message
let msg = Message::builder()
    .id(42)
    .query_str("/status")
    .query_format(QueryFormat::JsonPointer)
    .body_json(&serde_json::json!({"ping": true}))?
    .build();

// Serialize to bytes and back
let bytes = msg.to_vec();
let parsed = repe::Message::from_slice(&bytes)?;

assert_eq!(parsed.header.id, 42);
assert_eq!(parsed.header.body_format, BodyFormat::Json as u16);
let val: serde_json::Value = parsed.json_body()?;
assert_eq!(val["ping"], true);

use repe::{Message, QueryFormat, BodyFormat};

// Build a BEVE message
let msg = Message::builder()
    .id(43)
    .query_str("/status")
    .query_format(QueryFormat::JsonPointer)
    .body_beve(&serde_json::json!({"ping": true}))?
    .build();

let bytes = msg.to_vec();
let parsed = repe::Message::from_slice(&bytes)?;

assert_eq!(parsed.header.body_format, BodyFormat::Beve as u16);
let val: serde_json::Value = parsed.beve_body()?;
assert_eq!(val["ping"], true);

Examples

• examples/json_roundtrip.rs – construct/serialize/parse a JSON message.
• examples/server.rs – run a JSON-pointer server (TCP).
• examples/client.rs – call the server routes.
• examples/registry_server.rs – serve a dynamic registry under a path prefix.
• examples/registry_roundtrip.rs – local registry READ/WRITE/CALL roundtrip.
• examples/async_server.rs – tokio-based async server.
• examples/async_client.rs – tokio-based async client.

Notes

• BEVE helpers encode/decode via serde, so your existing request/response types continue to work.
• The header reserved field is currently ignored (per spec receivers must not reject non-zero values).
• The header length is validated to be 48 + query_length + body_length.

JSON Pointer Routing and Typed Handlers

• Router keys are JSON Pointer paths (e.g., /ping, /echo, /status). Raw-binary queries are rejected with an explicit Invalid query error.

• Add JSON Value handlers with .with("/path", |v: serde_json::Value| -> Result<Value, (ErrorCode,String)>).

• Add typed handlers with .with_typed("/path", |req: T| -> Result<R, (ErrorCode,String)>) where T: Deserialize, R: Serialize.

  • Typed handlers auto-deserialize JSON, UTF-8, or BEVE bodies into T. Responses default to JSON.
  • Wrap the return value with TypedResponse::beve(...) / TypedResponse::utf8(...) / etc. to pick a different response [BodyFormat].
  • If a body arrives with an unsupported format for typed handlers, the server returns Invalid body.

• Attach pre-request middleware with .with_middleware(|req, next| { /* auth/logging */ next.run(req) }) to centralize auth, validation, or tracing without hand-wrapping handlers.

• Implement the pluggable trait JsonTypedHandler to attach methods from a service type:

use repe::{Router, JsonTypedHandler, ErrorCode};
use serde::{Deserialize, Serialize};

#[derive(Deserialize)]
struct Input { name: String }
#[derive(Serialize)]
struct Output { greeting: String }

struct Greeter;
impl JsonTypedHandler for Greeter {
    type In = Input;
    type Out = Output;
    fn call(&self, input: Self::In) -> Result<Self::Out, (ErrorCode, String)> {
        Ok(Output { greeting: format!("Hello, {}!", input.name) })
    }
}

let router = Router::new().with_handler("/greet", Greeter);

Async (tokio)

• Use AsyncServer and AsyncClient for asynchronous operation with tokio.
• See examples/async_server.rs and examples/async_client.rs.

Fleet (Multi-Node Control)

• Use Fleet / AsyncFleet to manage multiple TCP REPE servers as one logical unit.
• Use UniUdpFleet for fire-and-forget UDP fanout (enable with --features fleet-udp).
• TCP retry policy retries transport/I/O failures only; application-level server errors are returned without retry.
• See docs/fleet.md for complete API details.

use repe::{Fleet, FleetOptions, NodeConfig, RetryPolicy};
use serde_json::json;
use std::time::Duration;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let fleet = Fleet::with_options(
        vec![
            NodeConfig::new("127.0.0.1", 8081)?
                .with_name("node-1")?
                .with_tags(["compute"]),
            NodeConfig::new("127.0.0.1", 8082)?
                .with_name("node-2")?
                .with_tags(["compute", "primary"]),
        ],
        FleetOptions {
            default_timeout: Duration::from_secs(2),
            retry_policy: RetryPolicy {
                max_attempts: 3,
                delay: Duration::from_millis(100),
            },
        },
    )?;

    let _ = fleet.connect_all();
    let status = fleet.broadcast_json("/status", None, &[] as &[&str]);
    let total = fleet.map_reduce_json(
        "/compute",
        Some(&json!({"value": 10})),
        &["compute"],
        |results| {
            results
                .into_iter()
                .filter_map(|r| r.value.and_then(|v| v["result"].as_i64()))
                .sum::<i64>()
        },
    );
    println!("total={total}, nodes={}", status.len());
    Ok(())
}

use repe::{AsyncFleet, FleetOptions, NodeConfig, RetryPolicy};
use serde_json::json;
use std::time::Duration;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let fleet = AsyncFleet::with_options(
        vec![NodeConfig::new("127.0.0.1", 8081)?.with_name("node-1")?],
        FleetOptions {
            default_timeout: Duration::from_secs(2),
            retry_policy: RetryPolicy {
                max_attempts: 3,
                delay: Duration::from_millis(100),
            },
        },
    )?;

    let _ = fleet.connect_all().await;
    let res = fleet
        .call_json("node-1", "/status", Some(&json!({})))
        .await?;
    assert!(res.succeeded());
    Ok(())
}

use repe::{UniUdpFleet, UniUdpNodeConfig};
use serde_json::json;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let fleet = UniUdpFleet::new(vec![
        UniUdpNodeConfig::new("127.0.0.1", 5001)?
            .with_name("edge-a")?
            .with_tags(["edge"]),
        UniUdpNodeConfig::new("127.0.0.1", 5002)?
            .with_name("edge-b")?
            .with_tags(["edge"]),
    ])?;

    let sent = fleet.send_notify("/heartbeat", Some(&json!({"source": "controller"})), &["edge"]);
    assert!(sent.values().all(|result| result.succeeded()));
    Ok(())
}

Server

• Build a router and serve TCP:

use repe::{Router, Server};
use serde_json::json;
use std::time::Duration;

let router = Router::new()
    .with_middleware(|req, next| {
        if let Ok(path) = req.query_str() {
            println!("incoming request for {path}");
        }
        next.run(req)
    })
    .with("/ping", |_v| Ok(json!({"pong": true})))
    .with("/echo", |v| Ok(json!({"echo": v})))
    .with("/status", |_v| Ok(json!({"status": "ok"})));

let server = Server::new(router)
    .read_timeout(Some(Duration::from_secs(120)))
    .write_timeout(Some(Duration::from_secs(120)));
let listener = server.listen("127.0.0.1:8081")?;
server.serve(listener)?;

• Register a struct and expose its fields/methods through JSON pointer paths:

use repe::Router;
use serde::{Deserialize, Serialize};
use serde_json::json;

#[derive(Default, Serialize, Deserialize, repe::RepeStruct)]
#[repe(methods(
    greet(&self) -> String,
    set_status(&mut self, new_status: String) -> (),
    reset_metrics(&mut self) -> ()
))]
struct Device {
    id: String,
    status: String,
    #[repe(nested)]
    metrics: Metrics,
}

#[derive(Default, Serialize, Deserialize, repe::RepeStruct)]
struct Metrics {
    temperature: f64,
    humidity: f64,
}

impl Device {
    fn greet(&self) -> String {
        format!("device {} reporting {}", self.id, self.status)
    }

    fn set_status(&mut self, new_status: String) {
        self.status = new_status;
    }

    fn reset_metrics(&mut self) {
        self.metrics = Metrics::default();
    }
}

let mut router = Router::new();
let device_handle = router.register_struct("/device", Device::default());

// Update initial state before serving.
{
    let mut device = device_handle.lock().unwrap();
    device.id = "sensor-42".into();
    device.status = "online".into();
    device.metrics.temperature = 21.5;
    device.metrics.humidity = 0.55;
}

// Example calls (JSON Pointer paths):
// - `/device/greet` -> "device sensor-42 reporting online"
// - `/device/status` with body "offline" writes the field and returns null
// - `/device/metrics/temperature` reads the nested value (21.5)
// - `/device/reset_metrics` zeroes out the metrics

Router handles `Arc<L>` for any lock implementing `repe::Lockable<T>`, so you can swap in
`tokio::sync::Mutex`/`RwLock` (via their `blocking_*` APIs) or enable the optional
`parking-lot` feature to use `parking_lot::Mutex`/`RwLock` without extra wrapper types.

Registry (Dynamic Routing)

• Mount a Registry on any path prefix with Router::with_registry("/api/v1", registry).
• Registry request semantics:
  • Empty body => READ value.
  • Non-empty body + function target => CALL function.
  • Non-empty body + non-function target => WRITE value.
• See docs/registry.md for full behavior, format decoding details, and client examples.

use repe::{ErrorCode, Registry, Router, Server};
use serde_json::{Value, json};
use std::sync::Arc;

let registry = Arc::new(Registry::new());
registry.register_value("/counter", json!(0))?;
registry.register_function("/add", |params| {
    let Some(Value::Object(map)) = params else {
        return Err((ErrorCode::InvalidBody, "expected object body".into()));
    };
    let a = map.get("a").and_then(Value::as_i64).unwrap_or(0);
    let b = map.get("b").and_then(Value::as_i64).unwrap_or(0);
    Ok(json!({"result": a + b}))
})?;

let router = Router::new().with_registry("/api/v1", Arc::clone(&registry));
let server = Server::new(router);
let listener = server.listen("127.0.0.1:8082")?;
server.serve(listener)?;

Client

• Connect and call JSON-pointer routes with JSON bodies:

use repe::Client;
use serde::{Deserialize, Serialize};
use serde_json::json;

#[derive(Serialize)]
struct AddReq {
    a: i64,
    b: i64,
}

#[derive(Deserialize)]
struct AddResp {
    sum: i64,
}

let client = Client::connect("127.0.0.1:8081")?;
let pong = client.call_json("/ping", &json!({}))?;
assert_eq!(pong["pong"], true);

let typed: AddResp = client.call_typed_json("/add", &AddReq { a: 2, b: 3 })?;
assert_eq!(typed.sum, 5);

client.notify_typed_json("/jobs/refresh", &AddReq { a: 0, b: 0 })?;
client.notify_typed_beve("/jobs/refresh_beve", &AddReq { a: 1, b: 2 })?;

Typed helpers work for BEVE payloads too:

let beve_sum: AddResp = client.call_typed_beve("/add", &AddReq { a: 4, b: 5 })?;
assert_eq!(beve_sum.sum, 9);

Registry-oriented client helpers:

• Empty-body READs: registry_read("/api/v1/counter") or call_message(...)
• Typed READs: registry_read_typed::<_, MyType>(...)
• JSON WRITE/CALL helpers: registry_write_json(...) and registry_call_json(...)
• Custom wire formats: call_with_formats(...) and notify_with_formats(...)

Multiplexed calls, timeouts, and batching

• Client and AsyncClient can run multiple in-flight requests on one connection.
• Clone the client handle and issue calls concurrently; responses are matched by request id even if the server replies out of order.
• Use per-call timeout helpers:
  • call_json_with_timeout
  • call_typed_json_with_timeout
  • call_typed_beve_with_timeout
• Use batch helpers for JSON calls:
  • batch_json(Vec<(String, Value)>)
  • batch_json_with_timeout(Vec<(String, Value)>, Duration)

Notify semantics

• If a request is marked notify = true, the server will process the handler but will not send a response.
• In the protocol, the id still increments client-side, but no matching response should be expected.
• The Client::notify_json and AsyncClient::notify_json helpers set the flag accordingly.
• Client::notify_typed_json / Client::notify_typed_beve and their async counterparts send typed payloads without waiting for a response, mirroring the call helpers.

Error handling

• Errors are returned “in-band” as responses with ec != Ok and a UTF‑8 body describing the error.
• Common mappings:
  • Header parse/validation issues → InvalidHeader or ParseError.
  • JSON deserialization/serialization issues → ParseError.
  • Missing routes → MethodNotFound with the requested path in the message.
  • Application failures from handlers → return (ErrorCode, String) to control both fields.
• Clients surface mismatched protocol versions as RepeError::VersionMismatch.
• Responses with unknown request IDs are logged and dropped by default (including late responses for timed-out requests).
• For bounded latency, prefer call_*_with_timeout APIs so a dropped response ID cannot leave a call waiting indefinitely.

Async usage (minimal end‑to‑end)

use repe::{Router, AsyncServer, AsyncClient};
use serde::{Deserialize, Serialize};
use serde_json::json;

# #[tokio::main]
# async fn main() -> std::io::Result<()> {
let router = Router::new().with_json("/ping", |_v| Ok(json!({"pong": true})));
let listener = AsyncServer::listen(("127.0.0.1", 0)).await?;
let addr = listener.local_addr()?;
tokio::spawn(async move { let _ = AsyncServer::new(router).serve(listener).await; });

#[derive(Serialize)]
struct AddReq {
    a: i64,
    b: i64,
}

#[derive(Deserialize)]
struct AddResp {
    sum: i64,
}

let client = AsyncClient::connect(addr).await.unwrap();
let pong = client.call_json("/ping", &json!({})).await.unwrap();
assert_eq!(pong["pong"], true);

let typed: AddResp = client
    .call_typed_json("/add", &AddReq { a: 8, b: 1 })
    .await
    .unwrap();
assert_eq!(typed.sum, 9);

let beve: AddResp = client
    .call_typed_beve("/add", &AddReq { a: 5, b: 6 })
    .await
    .unwrap();
assert_eq!(beve.sum, 11);
# Ok(()) }

Running the examples

cargo run --example server
cargo run --example client
cargo run --example registry_server
cargo run --example registry_roundtrip
cargo run --example async_server
cargo run --example async_client

Design overview

• Fixed header size is 48 bytes (HEADER_SIZE) followed by query and body payloads.
• All numeric fields are little‑endian. Header length equals 48 + query_length + body_length and is validated.
• query_format/body_format use the enums in repe::constants.
• Suggested query format is JSON Pointer (/path/to/resource).

JSON Pointer helpers

• parse_json_pointer splits a pointer into unescaped tokens.
• eval_json_pointer indexes into a serde_json::Value using array indices or object keys.

Testing

• Run cargo test to execute unit and integration tests. The crate denies warnings and includes async tests; you’ll need a recent tokio.
• Example integration tests cover sync/async server + client calls, unknown routes, handler error mapping, ID mismatches, and timeouts.

License

• MIT, see LICENSE.