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feat(rpc): add GET /lean/v0/config/spec (#456)
Adds the `GET /lean/v0/config/spec` endpoint, which exposes chain configuration parameters (slot duration, committee sizes, finality constants, etc.) as JSON. Allows external tools and cross-client integrations to discover runtime config without out-of-band coordination. Has unit tests and passed clippy. Stacked on #454.
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6 files changed

Lines changed: 110 additions & 8 deletions

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‎crates/common/types/src/constants.rs‎

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//! Protocol constants shared across crates.
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/// Fork digest embedded in every gossipsub topic string, as lowercase hex
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/// without a `0x` prefix.
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///
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/// The [leanSpec](https://github.com/leanEthereum/leanSpec/pull/622)
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/// currently mandates a dummy value shared across all clients; this will
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/// eventually be derived from the fork version and genesis validators root.
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// TODO: derive dynamically once the spec defines fork identification.
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pub const FORK_DIGEST: &str = "12345678";

‎crates/common/types/src/lib.rs‎

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@@ -2,6 +2,7 @@ pub mod aggregator;
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pub mod attestation;
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pub mod block;
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pub mod checkpoint;
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pub mod constants;
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pub mod genesis;
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pub mod primitives;
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pub mod signature;

‎crates/net/p2p/src/gossipsub/messages.rs‎

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/// Fork digest embedded in every gossipsub topic string, as lowercase hex
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/// without a `0x` prefix.
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///
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/// The [leanSpec](https://github.com/leanEthereum/leanSpec/pull/622)
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/// currently mandates a dummy value shared across all clients; this will
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/// eventually be derived from the fork version and genesis validators root.
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// TODO: derive dynamically once the spec defines fork identification.
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pub const FORK_DIGEST: &str = "12345678";
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pub use ethlambda_types::constants::FORK_DIGEST;
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/// Topic kind for block gossip
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pub const BLOCK_TOPIC_KIND: &str = "block";

‎crates/net/rpc/src/lib.rs‎

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@@ -15,6 +15,7 @@ mod fork_choice;
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mod genesis;
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mod heap_profiling;
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pub mod metrics;
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mod spec;
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pub mod test_driver;
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pub(crate) use base::json_response;
@@ -102,6 +103,7 @@ fn build_api_router(store: Store) -> Router {
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.merge(fork_choice::routes())
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.merge(admin::routes())
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.merge(genesis::routes())
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.merge(spec::routes())
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.with_state(store)
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}
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‎crates/net/rpc/src/spec.rs‎

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use axum::{Router, response::IntoResponse, routing::get};
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use ethlambda_blockchain::{INTERVALS_PER_SLOT, MILLISECONDS_PER_INTERVAL, MILLISECONDS_PER_SLOT};
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use ethlambda_storage::Store;
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use ethlambda_types::{constants::FORK_DIGEST, state::HISTORICAL_ROOTS_LIMIT};
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use serde::Serialize;
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use crate::json_response;
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#[derive(Serialize)]
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struct SpecResponse {
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#[serde(rename = "MILLISECONDS_PER_SLOT")]
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ms_per_slot: u64,
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#[serde(rename = "INTERVALS_PER_SLOT")]
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intervals_per_slot: u64,
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#[serde(rename = "MILLISECONDS_PER_INTERVAL")]
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ms_per_interval: u64,
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#[serde(rename = "HISTORICAL_ROOTS_LIMIT")]
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historical_roots_limit: u64,
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#[serde(rename = "FORK_DIGEST")]
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fork_digest: &'static str,
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}
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async fn get_spec() -> impl IntoResponse {
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json_response(SpecResponse {
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ms_per_slot: MILLISECONDS_PER_SLOT,
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intervals_per_slot: INTERVALS_PER_SLOT,
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ms_per_interval: MILLISECONDS_PER_INTERVAL,
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historical_roots_limit: HISTORICAL_ROOTS_LIMIT as u64,
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fork_digest: FORK_DIGEST,
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})
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}
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pub(crate) fn routes() -> Router<Store> {
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Router::new().route("/lean/v0/config/spec", get(get_spec))
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}
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#[cfg(test)]
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mod tests {
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use super::FORK_DIGEST;
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use crate::test_utils::create_test_state;
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use axum::{
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body::Body,
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http::{Request, StatusCode},
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};
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use ethlambda_blockchain::{
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INTERVALS_PER_SLOT, MILLISECONDS_PER_INTERVAL, MILLISECONDS_PER_SLOT,
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};
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use ethlambda_storage::{Store, backend::InMemoryBackend};
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use ethlambda_types::state::HISTORICAL_ROOTS_LIMIT;
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use http_body_util::BodyExt;
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use std::sync::Arc;
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use tower::ServiceExt;
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#[tokio::test]
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async fn spec_returns_lean_constants() {
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let store = Store::from_anchor_state(Arc::new(InMemoryBackend::new()), create_test_state());
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let app = crate::build_api_router(store);
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let resp = app
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.oneshot(
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Request::builder()
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.uri("/lean/v0/config/spec")
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.body(Body::empty())
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.unwrap(),
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)
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.await
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.unwrap();
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assert_eq!(resp.status(), StatusCode::OK);
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let body = resp.into_body().collect().await.unwrap().to_bytes();
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let json: serde_json::Value = serde_json::from_slice(&body).unwrap();
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assert_eq!(json["MILLISECONDS_PER_SLOT"], MILLISECONDS_PER_SLOT);
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assert_eq!(json["INTERVALS_PER_SLOT"], INTERVALS_PER_SLOT);
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assert_eq!(json["MILLISECONDS_PER_INTERVAL"], MILLISECONDS_PER_INTERVAL);
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assert_eq!(
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json["HISTORICAL_ROOTS_LIMIT"],
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HISTORICAL_ROOTS_LIMIT as u64
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);
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assert_eq!(json["FORK_DIGEST"], FORK_DIGEST);
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}
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}

‎docs/rpc.md‎

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| Method | Path | Response | Description |
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|--------|------|----------|-------------|
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| `GET` | `/lean/v0/health` | JSON | Liveness check |
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| `GET` | `/lean/v0/config/spec` | JSON | Protocol constants the node runs with |
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| `GET` | `/lean/v0/genesis` | JSON | Genesis time and validator count |
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| `GET` | `/lean/v0/states/finalized` | SSZ | Latest finalized `State` |
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| `GET` | `/lean/v0/blocks/finalized` | SSZ | Latest finalized `SignedBlock` |
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{"status":"healthy","service":"lean-rpc-api"}
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```
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### `GET /lean/v0/config/spec`
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Protocol constants the node was built with. Keys mirror the leanSpec constant names:
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```json
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{
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"MILLISECONDS_PER_SLOT": 4000,
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"INTERVALS_PER_SLOT": 5,
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"MILLISECONDS_PER_INTERVAL": 800,
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"HISTORICAL_ROOTS_LIMIT": 262144,
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"FORK_DIGEST": "12345678"
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}
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```
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`FORK_DIGEST` is the 4-byte hex string (no `0x` prefix) embedded in gossipsub topic names.
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### `GET /lean/v0/genesis`
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```json

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