Ssz state (#1749)

## Issue Addressed

NA

## Proposed Changes

Adds a `lighthouse/beacon/states/:state_id/ssz` endpoint to allow us to pull the genesis state from the API.

## Additional Info

NA

Cargo.lock

@@ -1574,6 +1574,7 @@ dependencies = [
  "bytes 0.5.6",
  "eth2_keystore",
  "eth2_libp2p",
+ "eth2_ssz",
  "hex 0.4.2",
  "libsecp256k1",
  "procinfo",
@@ -2461,6 +2462,7 @@ dependencies = [
  "eth1",
  "eth2",
  "eth2_libp2p",
+ "eth2_ssz",
  "fork_choice",
  "hex 0.4.2",
  "lazy_static",

beacon_node/http_api/Cargo.toml

@@ -24,6 +24,7 @@ lighthouse_metrics = { path = "../../common/lighthouse_metrics" }
 lazy_static = "1.4.0"
 warp_utils = { path = "../../common/warp_utils" }
 slot_clock = { path = "../../common/slot_clock" }
+eth2_ssz = { path = "../../consensus/ssz" }
 bs58 = "0.3.1"
 
 [dev-dependencies]

beacon_node/http_api/src/lib.rs

@@ -28,6 +28,7 @@ use parking_lot::Mutex;
 use serde::{Deserialize, Serialize};
 use slog::{crit, error, info, trace, warn, Logger};
 use slot_clock::SlotClock;
+use ssz::Encode;
 use state_id::StateId;
 use state_processing::per_slot_processing;
 use std::borrow::Cow;
@@ -41,7 +42,7 @@ use types::{
     Hash256, ProposerSlashing, PublicKey, RelativeEpoch, SignedAggregateAndProof,
     SignedBeaconBlock, SignedVoluntaryExit, Slot, YamlConfig,
 };
-use warp::Filter;
+use warp::{http::Response, Filter};
 use warp_utils::task::{blocking_json_task, blocking_task};
 
 const API_PREFIX: &str = "eth";
@@ -1768,7 +1769,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path::param::<Epoch>())
         .and(warp::path("global"))
         .and(warp::path::end())
-        .and(chain_filter)
+        .and(chain_filter.clone())
         .and_then(|epoch: Epoch, chain: Arc<BeaconChain<T>>| {
             blocking_json_task(move || {
                 validator_inclusion::global_validator_inclusion_data(epoch, &chain)
@@ -1776,6 +1777,30 @@ pub fn serve<T: BeaconChainTypes>(
             })
         });
 
+    // GET lighthouse/beacon/states/{state_id}/ssz
+    let get_lighthouse_beacon_states_ssz = warp::path("lighthouse")
+        .and(warp::path("beacon"))
+        .and(warp::path("states"))
+        .and(warp::path::param::<StateId>())
+        .and(warp::path("ssz"))
+        .and(warp::path::end())
+        .and(chain_filter)
+        .and_then(|state_id: StateId, chain: Arc<BeaconChain<T>>| {
+            blocking_task(move || {
+                let state = state_id.state(&chain)?;
+                Response::builder()
+                    .status(200)
+                    .header("Content-Type", "application/ssz")
+                    .body(state.as_ssz_bytes())
+                    .map_err(|e| {
+                        warp_utils::reject::custom_server_error(format!(
+                            "failed to create response: {}",
+                            e
+                        ))
+                    })
+            })
+        });
+
     // Define the ultimate set of routes that will be provided to the server.
     let routes = warp::get()
         .and(
@@ -1818,6 +1843,7 @@ pub fn serve<T: BeaconChainTypes>(
                 .or(get_lighthouse_proto_array.boxed())
                 .or(get_lighthouse_validator_inclusion_global.boxed())
                 .or(get_lighthouse_validator_inclusion.boxed())
+                .or(get_lighthouse_beacon_states_ssz.boxed())
                 .boxed(),
         )
         .or(warp::post()

beacon_node/http_api/tests/tests.rs

@@ -1571,6 +1571,23 @@ impl ApiTester {
 
         self
     }
+
+    pub async fn test_get_lighthouse_beacon_states_ssz(self) -> Self {
+        for state_id in self.interesting_state_ids() {
+            let result = self
+                .client
+                .get_lighthouse_beacon_states_ssz(&state_id)
+                .await
+                .unwrap();
+
+            let mut expected = self.get_state(state_id);
+            expected.as_mut().map(|state| state.drop_all_caches());
+
+            assert_eq!(result, expected, "{:?}", state_id);
+        }
+
+        self
+    }
 }
 
 #[tokio::test(core_threads = 2)]
@@ -1871,5 +1888,7 @@ async fn lighthouse_endpoints() {
         .test_get_lighthouse_validator_inclusion()
         .await
         .test_get_lighthouse_validator_inclusion_global()
+        .await
+        .test_get_lighthouse_beacon_states_ssz()
         .await;
 }

book/src/api-lighthouse.md

@@ -177,3 +177,17 @@ See [Validator Inclusion APIs](./validator-inclusion.md).
 ### `/lighthouse/validator_inclusion/{epoch}/global`
 
 See [Validator Inclusion APIs](./validator-inclusion.md).
+
+### `/lighthouse/beacon/states/{state_id}/ssz`
+
+Obtains a `BeaconState` in SSZ bytes. Useful for obtaining a genesis state.
+
+The `state_id` parameter is identical to that used in the [Standard Eth2.0 API
+`beacon/state`
+routes](https://ethereum.github.io/eth2.0-APIs/#/Beacon/getStateRoot).
+
+```bash
+curl -X GET "http://localhost:5052/lighthouse/beacon/states/0/ssz" | jq
+```
+
+*Example omitted for brevity, the body simply contains SSZ bytes.*

common/eth2/Cargo.toml

@@ -21,6 +21,7 @@ libsecp256k1 = "0.3.5"
 ring = "0.16.12"
 bytes = "0.5.6"
 account_utils = { path = "../../common/account_utils" }
+eth2_ssz = { path = "../../consensus/ssz" }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 psutil = { version = "3.2.0", optional = true }

common/eth2/src/lib.rs

@@ -40,6 +40,8 @@ pub enum Error {
     MissingSignatureHeader,
     /// The server returned an invalid JSON response.
     InvalidJson(serde_json::Error),
+    /// The server returned an invalid SSZ response.
+    InvalidSsz(ssz::DecodeError),
 }
 
 impl Error {
@@ -54,6 +56,7 @@ impl Error {
             Error::InvalidSignatureHeader => None,
             Error::MissingSignatureHeader => None,
             Error::InvalidJson(_) => None,
+            Error::InvalidSsz(_) => None,
         }
     }
 }

common/eth2/src/lighthouse.rs

@@ -1,11 +1,14 @@
 //! This module contains endpoints that are non-standard and only available on Lighthouse servers.
 
 use crate::{
-    types::{Epoch, EthSpec, GenericResponse, ValidatorId},
-    BeaconNodeHttpClient, Error,
+    ok_or_error,
+    types::{BeaconState, Epoch, EthSpec, GenericResponse, ValidatorId},
+    BeaconNodeHttpClient, Error, StateId, StatusCode,
 };
 use proto_array::core::ProtoArray;
+use reqwest::IntoUrl;
 use serde::{Deserialize, Serialize};
+use ssz::Decode;
 
 pub use eth2_libp2p::{types::SyncState, PeerInfo};
 
@@ -143,6 +146,27 @@ impl Health {
 }
 
 impl BeaconNodeHttpClient {
+    /// Perform a HTTP GET request, returning `None` on a 404 error.
+    async fn get_bytes_opt<U: IntoUrl>(&self, url: U) -> Result<Option<Vec<u8>>, Error> {
+        let response = self.client.get(url).send().await.map_err(Error::Reqwest)?;
+        match ok_or_error(response).await {
+            Ok(resp) => Ok(Some(
+                resp.bytes()
+                    .await
+                    .map_err(Error::Reqwest)?
+                    .into_iter()
+                    .collect::<Vec<_>>(),
+            )),
+            Err(err) => {
+                if err.status() == Some(StatusCode::NOT_FOUND) {
+                    Ok(None)
+                } else {
+                    Err(err)
+                }
+            }
+        }
+    }
+
     /// `GET lighthouse/health`
     pub async fn get_lighthouse_health(&self) -> Result<GenericResponse<Health>, Error> {
         let mut path = self.server.clone();
@@ -221,4 +245,25 @@ impl BeaconNodeHttpClient {
 
         self.get(path).await
     }
+
+    /// `GET lighthouse/beacon/states/{state_id}/ssz`
+    pub async fn get_lighthouse_beacon_states_ssz<E: EthSpec>(
+        &self,
+        state_id: &StateId,
+    ) -> Result<Option<BeaconState<E>>, Error> {
+        let mut path = self.server.clone();
+
+        path.path_segments_mut()
+            .map_err(|()| Error::InvalidUrl(self.server.clone()))?
+            .push("lighthouse")
+            .push("beacon")
+            .push("states")
+            .push(&state_id.to_string())
+            .push("ssz");
+
+        self.get_bytes_opt(path)
+            .await?
+            .map(|bytes| BeaconState::from_ssz_bytes(&bytes).map_err(Error::InvalidSsz))
+            .transpose()
+    }
 }