Bootstrap (#501)

* Renamed fork_choice::process_attestation_from_block

* Processing attestation in fork choice

* Retrieving state from store and checking signature

* Looser check on beacon state validity.

* Cleaned up get_attestation_state

* Expanded fork choice api to provide latest validator message.

* Checking if the an attestation contains a latest message

* Correct process_attestation error handling.

* Copy paste error in comment fixed.

* Tidy ancestor iterators

* Getting attestation slot via helper method

* Refactored attestation creation in test utils

* Revert "Refactored attestation creation in test utils"

This reverts commit 4d277fe4239a7194758b18fb5c00dfe0b8231306.

* Integration tests for free attestation processing

* Implicit conflicts resolved.

* formatting

* Do first pass on Grants code

* Add another attestation processing test

* Tidy attestation processing

* Remove old code fragment

* Add non-compiling half finished changes

* Simplify, fix bugs, add tests for chain iters

* Remove attestation processing from op pool

* Fix bug with fork choice, tidy

* Fix overly restrictive check in fork choice.

* Ensure committee cache is build during attn proc

* Ignore unknown blocks at fork choice

* Various minor fixes

* Make fork choice write lock in to read lock

* Remove unused method

* Tidy comments

* Fix attestation prod. target roots change

* Fix compile error in store iters

* Reject any attestation prior to finalization

* Begin metrics refactor

* Move beacon_chain to new metrics structure.

* Make metrics not panic if already defined

* Use global prometheus gather at rest api

* Unify common metric fns into a crate

* Add heavy metering to block processing

* Remove hypen from prometheus metric name

* Add more beacon chain metrics

* Add beacon chain persistence metric

* Prune op pool on finalization

* Add extra prom beacon chain metrics

* Prefix BeaconChain metrics with "beacon_"

* Add more store metrics

* Add basic metrics to libp2p

* Add metrics to HTTP server

* Remove old `http_server` crate

* Update metrics names to be more like standard

* Fix broken beacon chain metrics, add slot clock metrics

* Add lighthouse_metrics gather fn

* Remove http args

* Fix wrong state given to op pool prune

* Make prom metric names more consistent

* Add more metrics, tidy existing metrics

* Fix store block read metrics

* Tidy attestation metrics

* Fix minor PR comments

* Fix minor PR comments

* Remove duplicated attestation finalization check

* Remove awkward `let` statement

* Add first attempts at HTTP bootstrap

* Add beacon_block methods to rest api

* Fix serde for block.body.grafitti

* Allow travis failures on beta (see desc)

There's a non-backward compatible change in `cargo fmt`. Stable and beta
do not agree.

* Add network routes to API

* Fix rustc warnings

* Add best_slot method

* Add --bootstrap arg to beacon node

* Get bootstrapper working for ENR address

* Store intermediate states during block processing

* Allow bootstrapper to scrape libp2p address

* Update bootstrapper libp2p address finding

* Add comments

* Tidy API to be more consistent with recent decisions

* Address some review comments

* Make BeaconChainTypes Send + Sync + 'static

* Add `/network/listen_port` API endpoint

* Abandon starting the node if libp2p doesn't start

* Update bootstrapper for API changes

* Remove unnecessary trait bounds

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -77,7 +77,7 @@ pub enum AttestationProcessingOutcome {
     Invalid(AttestationValidationError),
 }
 
-pub trait BeaconChainTypes {
+pub trait BeaconChainTypes: Send + Sync + 'static {
     type Store: store::Store;
     type SlotClock: slot_clock::SlotClock;
     type LmdGhost: LmdGhost<Self::Store, Self::EthSpec>;
@@ -870,9 +870,16 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
 
         let catchup_timer = metrics::start_timer(&metrics::BLOCK_PROCESSING_CATCHUP_STATE);
 
+        // Keep a list of any states that were "skipped" (block-less) in between the parent state
+        // slot and the block slot. These will need to be stored in the database.
+        let mut intermediate_states = vec![];
+
         // Transition the parent state to the block slot.
         let mut state: BeaconState<T::EthSpec> = parent_state;
-        for _ in state.slot.as_u64()..block.slot.as_u64() {
+        for i in state.slot.as_u64()..block.slot.as_u64() {
+            if i > 0 {
+                intermediate_states.push(state.clone());
+            }
             per_slot_processing(&mut state, &self.spec)?;
         }
 
@@ -911,6 +918,22 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
 
         let db_write_timer = metrics::start_timer(&metrics::BLOCK_PROCESSING_DB_WRITE);
 
+        // Store all the states between the parent block state and this blocks slot before storing
+        // the final state.
+        for (i, intermediate_state) in intermediate_states.iter().enumerate() {
+            // To avoid doing an unnecessary tree hash, use the following (slot + 1) state's
+            // state_roots field to find the root.
+            let following_state = match intermediate_states.get(i + 1) {
+                Some(following_state) => following_state,
+                None => &state,
+            };
+            let intermediate_state_root =
+                following_state.get_state_root(intermediate_state.slot)?;
+
+            self.store
+                .put(&intermediate_state_root, intermediate_state)?;
+        }
+
         // Store the block and state.
         self.store.put(&block_root, &block)?;
         self.store.put(&state_root, &state)?;

beacon_node/beacon_chain/src/test_utils.rs

@@ -54,7 +54,7 @@ where
 
 impl<L, E> BeaconChainTypes for CommonTypes<L, E>
 where
-    L: LmdGhost<MemoryStore, E>,
+    L: LmdGhost<MemoryStore, E> + 'static,
     E: EthSpec,
 {
     type Store = MemoryStore;
@@ -69,7 +69,7 @@ where
 /// Used for testing.
 pub struct BeaconChainHarness<L, E>
 where
-    L: LmdGhost<MemoryStore, E>,
+    L: LmdGhost<MemoryStore, E> + 'static,
     E: EthSpec,
 {
     pub chain: BeaconChain<CommonTypes<L, E>>,

beacon_node/client/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 [dependencies]
 beacon_chain = { path = "../beacon_chain" }
 network = { path = "../network" }
+eth2-libp2p = { path = "../eth2-libp2p" }
 rpc = { path = "../rpc" }
 rest_api = { path = "../rest_api" }
 prometheus = "^0.6"
@@ -26,3 +27,5 @@ clap = "2.32.0"
 dirs = "1.0.3"
 exit-future = "0.1.3"
 futures = "0.1.25"
+reqwest = "0.9"
+url = "1.2"

beacon_node/client/src/beacon_chain_types.rs

@@ -1,3 +1,4 @@
+use crate::bootstrapper::Bootstrapper;
 use crate::error::Result;
 use crate::{config::GenesisState, ClientConfig};
 use beacon_chain::{
@@ -35,7 +36,11 @@ pub struct ClientType<S: Store, E: EthSpec> {
     _phantom_u: PhantomData<E>,
 }
 
-impl<S: Store, E: EthSpec + Clone> BeaconChainTypes for ClientType<S, E> {
+impl<S, E> BeaconChainTypes for ClientType<S, E>
+where
+    S: Store + 'static,
+    E: EthSpec,
+{
     type Store = S;
     type SlotClock = SystemTimeSlotClock;
     type LmdGhost = ThreadSafeReducedTree<S, E>;
@@ -74,6 +79,16 @@ where
             serde_yaml::from_reader(file)
                 .map_err(|e| format!("Unable to parse YAML genesis state file: {:?}", e))?
         }
+        GenesisState::HttpBootstrap { server } => {
+            let bootstrapper = Bootstrapper::from_server_string(server.to_string())
+                .map_err(|e| format!("Failed to initialize bootstrap client: {}", e))?;
+
+            let (state, _block) = bootstrapper
+                .genesis()
+                .map_err(|e| format!("Failed to bootstrap genesis state: {}", e))?;
+
+            state
+        }
     };
 
     let mut genesis_block = BeaconBlock::empty(&spec);

beacon_node/client/src/bootstrapper.rs

@@ -0,0 +1,210 @@
+use eth2_libp2p::{
+    multiaddr::{Multiaddr, Protocol},
+    Enr,
+};
+use reqwest::{Error as HttpError, Url};
+use serde::Deserialize;
+use std::borrow::Cow;
+use std::net::Ipv4Addr;
+use types::{BeaconBlock, BeaconState, Checkpoint, EthSpec, Hash256, Slot};
+use url::Host;
+
+#[derive(Debug)]
+enum Error {
+    InvalidUrl,
+    HttpError(HttpError),
+}
+
+impl From<HttpError> for Error {
+    fn from(e: HttpError) -> Error {
+        Error::HttpError(e)
+    }
+}
+
+/// Used to load "bootstrap" information from the HTTP API of another Lighthouse beacon node.
+///
+/// Bootstrapping information includes things like genesis and finalized states and blocks, and
+/// libp2p connection details.
+pub struct Bootstrapper {
+    url: Url,
+}
+
+impl Bootstrapper {
+    /// Parses the given `server` as a URL, instantiating `Self`.
+    pub fn from_server_string(server: String) -> Result<Self, String> {
+        Ok(Self {
+            url: Url::parse(&server).map_err(|e| format!("Invalid bootstrap server url: {}", e))?,
+        })
+    }
+
+    /// Build a multiaddr using the HTTP server URL that is not guaranteed to be correct.
+    ///
+    /// The address is created by querying the HTTP server for its listening libp2p addresses.
+    /// Then, we find the first TCP port in those addresses and combine the port with the URL of
+    /// the server.
+    ///
+    /// For example, the server `http://192.168.0.1` might end up with a `best_effort_multiaddr` of
+    /// `/ipv4/192.168.0.1/tcp/9000` if the server advertises a listening address of
+    /// `/ipv4/172.0.0.1/tcp/9000`.
+    pub fn best_effort_multiaddr(&self) -> Option<Multiaddr> {
+        let tcp_port = self.listen_port().ok()?;
+
+        let mut multiaddr = Multiaddr::with_capacity(2);
+
+        match self.url.host()? {
+            Host::Ipv4(addr) => multiaddr.push(Protocol::Ip4(addr)),
+            Host::Domain(s) => multiaddr.push(Protocol::Dns4(Cow::Borrowed(s))),
+            _ => return None,
+        };
+
+        multiaddr.push(Protocol::Tcp(tcp_port));
+
+        Some(multiaddr)
+    }
+
+    /// Returns the IPv4 address of the server URL, unless it contains a FQDN.
+    pub fn server_ipv4_addr(&self) -> Option<Ipv4Addr> {
+        match self.url.host()? {
+            Host::Ipv4(addr) => Some(addr),
+            _ => None,
+        }
+    }
+
+    /// Returns the servers ENR address.
+    pub fn enr(&self) -> Result<Enr, String> {
+        get_enr(self.url.clone()).map_err(|e| format!("Unable to get ENR: {:?}", e))
+    }
+
+    /// Returns the servers listening libp2p addresses.
+    pub fn listen_port(&self) -> Result<u16, String> {
+        get_listen_port(self.url.clone()).map_err(|e| format!("Unable to get listen port: {:?}", e))
+    }
+
+    /// Returns the genesis block and state.
+    pub fn genesis<T: EthSpec>(&self) -> Result<(BeaconState<T>, BeaconBlock<T>), String> {
+        let genesis_slot = Slot::new(0);
+
+        let block = get_block(self.url.clone(), genesis_slot)
+            .map_err(|e| format!("Unable to get genesis block: {:?}", e))?
+            .beacon_block;
+        let state = get_state(self.url.clone(), genesis_slot)
+            .map_err(|e| format!("Unable to get genesis state: {:?}", e))?
+            .beacon_state;
+
+        Ok((state, block))
+    }
+
+    /// Returns the most recent finalized state and block.
+    pub fn finalized<T: EthSpec>(&self) -> Result<(BeaconState<T>, BeaconBlock<T>), String> {
+        let slots_per_epoch = get_slots_per_epoch(self.url.clone())
+            .map_err(|e| format!("Unable to get slots per epoch: {:?}", e))?;
+        let finalized_slot = get_finalized_slot(self.url.clone(), slots_per_epoch.as_u64())
+            .map_err(|e| format!("Unable to get finalized slot: {:?}", e))?;
+
+        let block = get_block(self.url.clone(), finalized_slot)
+            .map_err(|e| format!("Unable to get finalized block: {:?}", e))?
+            .beacon_block;
+        let state = get_state(self.url.clone(), finalized_slot)
+            .map_err(|e| format!("Unable to get finalized state: {:?}", e))?
+            .beacon_state;
+
+        Ok((state, block))
+    }
+}
+
+fn get_slots_per_epoch(mut url: Url) -> Result<Slot, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("spec").push("slots_per_epoch");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    reqwest::get(url)?
+        .error_for_status()?
+        .json()
+        .map_err(Into::into)
+}
+
+fn get_finalized_slot(mut url: Url, slots_per_epoch: u64) -> Result<Slot, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("beacon").push("latest_finalized_checkpoint");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    let checkpoint: Checkpoint = reqwest::get(url)?.error_for_status()?.json()?;
+
+    Ok(checkpoint.epoch.start_slot(slots_per_epoch))
+}
+
+#[derive(Deserialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct StateResponse<T: EthSpec> {
+    pub root: Hash256,
+    pub beacon_state: BeaconState<T>,
+}
+
+fn get_state<T: EthSpec>(mut url: Url, slot: Slot) -> Result<StateResponse<T>, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("beacon").push("state");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    url.query_pairs_mut()
+        .append_pair("slot", &format!("{}", slot.as_u64()));
+
+    reqwest::get(url)?
+        .error_for_status()?
+        .json()
+        .map_err(Into::into)
+}
+
+#[derive(Deserialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct BlockResponse<T: EthSpec> {
+    pub root: Hash256,
+    pub beacon_block: BeaconBlock<T>,
+}
+
+fn get_block<T: EthSpec>(mut url: Url, slot: Slot) -> Result<BlockResponse<T>, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("beacon").push("block");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    url.query_pairs_mut()
+        .append_pair("slot", &format!("{}", slot.as_u64()));
+
+    reqwest::get(url)?
+        .error_for_status()?
+        .json()
+        .map_err(Into::into)
+}
+
+fn get_enr(mut url: Url) -> Result<Enr, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("network").push("enr");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    reqwest::get(url)?
+        .error_for_status()?
+        .json()
+        .map_err(Into::into)
+}
+
+fn get_listen_port(mut url: Url) -> Result<u16, Error> {
+    url.path_segments_mut()
+        .map(|mut url| {
+            url.push("network").push("listen_port");
+        })
+        .map_err(|_| Error::InvalidUrl)?;
+
+    reqwest::get(url)?
+        .error_for_status()?
+        .json()
+        .map_err(Into::into)
+}

beacon_node/client/src/config.rs

@@ -1,8 +1,8 @@
-use crate::Eth2Config;
+use crate::{Bootstrapper, Eth2Config};
 use clap::ArgMatches;
 use network::NetworkConfig;
 use serde_derive::{Deserialize, Serialize};
-use slog::{info, o, Drain};
+use slog::{info, o, warn, Drain};
 use std::fs::{self, OpenOptions};
 use std::path::PathBuf;
 use std::sync::Mutex;
@@ -46,6 +46,8 @@ pub enum GenesisState {
     },
     /// Load a YAML-encoded genesis state from a file.
     Yaml { file: PathBuf },
+    /// Use a HTTP server (running our REST-API) to load genesis and finalized states and blocks.
+    HttpBootstrap { server: String },
 }
 
 impl Default for Config {
@@ -147,6 +149,40 @@ impl Config {
             self.update_logger(log)?;
         };
 
+        // If the `--bootstrap` flag is provided, overwrite the default configuration.
+        if let Some(server) = args.value_of("bootstrap") {
+            do_bootstrapping(self, server.to_string(), &log)?;
+        }
+
         Ok(())
     }
 }
+
+/// Perform the HTTP bootstrapping procedure, reading an ENR and multiaddr from the HTTP server and
+/// adding them to the `config`.
+fn do_bootstrapping(config: &mut Config, server: String, log: &slog::Logger) -> Result<(), String> {
+    // Set the genesis state source.
+    config.genesis_state = GenesisState::HttpBootstrap {
+        server: server.to_string(),
+    };
+
+    let bootstrapper = Bootstrapper::from_server_string(server.to_string())?;
+
+    config.network.boot_nodes.push(bootstrapper.enr()?);
+
+    if let Some(server_multiaddr) = bootstrapper.best_effort_multiaddr() {
+        info!(
+            log,
+            "Estimated bootstrapper libp2p address";
+            "multiaddr" => format!("{:?}", server_multiaddr)
+        );
+        config.network.libp2p_nodes.push(server_multiaddr);
+    } else {
+        warn!(
+            log,
+            "Unable to estimate a bootstrapper libp2p address, this node may not find any peers."
+        );
+    }
+
+    Ok(())
+}

beacon_node/client/src/lib.rs

@@ -1,6 +1,7 @@
 extern crate slog;
 
 mod beacon_chain_types;
+mod bootstrapper;
 mod config;
 
 pub mod error;
@@ -21,7 +22,8 @@ use tokio::timer::Interval;
 pub use beacon_chain::BeaconChainTypes;
 pub use beacon_chain_types::ClientType;
 pub use beacon_chain_types::InitialiseBeaconChain;
-pub use config::Config as ClientConfig;
+pub use bootstrapper::Bootstrapper;
+pub use config::{Config as ClientConfig, GenesisState};
 pub use eth2_config::Eth2Config;
 
 /// Main beacon node client service. This provides the connection and initialisation of the clients
@@ -47,7 +49,7 @@ pub struct Client<T: BeaconChainTypes> {
 
 impl<T> Client<T>
 where
-    T: BeaconChainTypes + InitialiseBeaconChain<T> + Clone + 'static,
+    T: BeaconChainTypes + InitialiseBeaconChain<T> + Clone,
 {
     /// Generate an instance of the client. Spawn and link all internal sub-processes.
     pub fn new(
@@ -121,6 +123,7 @@ where
                 &client_config.rest_api,
                 executor,
                 beacon_chain.clone(),
+                network.clone(),
                 client_config.db_path().expect("unable to read datadir"),
                 &log,
             ) {

beacon_node/client/src/notifier.rs

@@ -17,11 +17,7 @@ pub const WARN_PEER_COUNT: usize = 1;
 /// durations.
 ///
 /// Presently unused, but remains for future use.
-pub fn run<T: BeaconChainTypes + Send + Sync + 'static>(
+pub fn run<T: BeaconChainTypes>(client: &Client<T>, executor: TaskExecutor, exit: Exit) {
-    client: &Client<T>,
-    executor: TaskExecutor,
-    exit: Exit,
-) {
     // notification heartbeat
     let interval = Interval::new(
         Instant::now(),

beacon_node/eth2-libp2p/src/behaviour.rs

@@ -78,6 +78,10 @@ impl<TSubstream: AsyncRead + AsyncWrite> Behaviour<TSubstream> {
             log: behaviour_log,
         })
     }
+
+    pub fn discovery(&self) -> &Discovery<TSubstream> {
+        &self.discovery
+    }
 }
 
 // Implement the NetworkBehaviourEventProcess trait so that we can derive NetworkBehaviour for Behaviour

beacon_node/eth2-libp2p/src/discovery.rs

@@ -103,6 +103,10 @@ impl<TSubstream> Discovery<TSubstream> {
         })
     }
 
+    pub fn local_enr(&self) -> &Enr {
+        self.discovery.local_enr()
+    }
+
     /// Manually search for peers. This restarts the discovery round, sparking multiple rapid
     /// queries.
     pub fn discover_peers(&mut self) {
@@ -120,6 +124,11 @@ impl<TSubstream> Discovery<TSubstream> {
         self.connected_peers.len()
     }
 
+    /// The current number of connected libp2p peers.
+    pub fn connected_peer_set(&self) -> &HashSet<PeerId> {
+        &self.connected_peers
+    }
+
     /// Search for new peers using the underlying discovery mechanism.
     fn find_peers(&mut self) {
         // pick a random NodeId

beacon_node/eth2-libp2p/src/lib.rs

@@ -17,12 +17,13 @@ pub use behaviour::PubsubMessage;
 pub use config::{
     Config as NetworkConfig, BEACON_ATTESTATION_TOPIC, BEACON_BLOCK_TOPIC, SHARD_TOPIC_PREFIX,
 };
+pub use libp2p::enr::Enr;
 pub use libp2p::gossipsub::{Topic, TopicHash};
 pub use libp2p::multiaddr;
 pub use libp2p::Multiaddr;
 pub use libp2p::{
     gossipsub::{GossipsubConfig, GossipsubConfigBuilder},
-    PeerId,
+    PeerId, Swarm,
 };
 pub use rpc::RPCEvent;
 pub use service::Libp2pEvent;

beacon_node/eth2-libp2p/src/service.rs

@@ -16,7 +16,7 @@ use libp2p::core::{
     upgrade::{InboundUpgradeExt, OutboundUpgradeExt},
 };
 use libp2p::{core, secio, PeerId, Swarm, Transport};
-use slog::{debug, info, trace, warn};
+use slog::{crit, debug, info, trace, warn};
 use std::fs::File;
 use std::io::prelude::*;
 use std::io::{Error, ErrorKind};
@@ -33,7 +33,7 @@ pub struct Service {
     //TODO: Make this private
     pub swarm: Swarm<Libp2pStream, Libp2pBehaviour>,
     /// This node's PeerId.
-    _local_peer_id: PeerId,
+    pub local_peer_id: PeerId,
     /// The libp2p logger handle.
     pub log: slog::Logger,
 }
@@ -69,10 +69,15 @@ impl Service {
                 log_address.push(Protocol::P2p(local_peer_id.clone().into()));
                 info!(log, "Listening on: {}", log_address);
             }
-            Err(err) => warn!(
+            Err(err) => {
-                log,
+                crit!(
-                "Cannot listen on: {} because: {:?}", listen_multiaddr, err
+                    log,
-            ),
+                    "Unable to listen on libp2p address";
+                    "error" => format!("{:?}", err),
+                    "listen_multiaddr" => format!("{}", listen_multiaddr),
+                );
+                return Err("Libp2p was unable to listen on the given listen address.".into());
+            }
         };
 
         // attempt to connect to user-input libp2p nodes
@@ -113,7 +118,7 @@ impl Service {
         info!(log, "Subscribed to topics: {:?}", subscribed_topics);
 
         Ok(Service {
-            _local_peer_id: local_peer_id,
+            local_peer_id,
             swarm,
             log,
         })

beacon_node/network/src/service.rs

@@ -5,7 +5,7 @@ use beacon_chain::{BeaconChain, BeaconChainTypes};
 use core::marker::PhantomData;
 use eth2_libp2p::Service as LibP2PService;
 use eth2_libp2p::Topic;
-use eth2_libp2p::{Libp2pEvent, PeerId};
+use eth2_libp2p::{Enr, Libp2pEvent, Multiaddr, PeerId, Swarm};
 use eth2_libp2p::{PubsubMessage, RPCEvent};
 use futures::prelude::*;
 use futures::Stream;
@@ -18,6 +18,7 @@ use tokio::sync::{mpsc, oneshot};
 /// Service that handles communication between internal services and the eth2_libp2p network service.
 pub struct Service<T: BeaconChainTypes> {
     libp2p_service: Arc<Mutex<LibP2PService>>,
+    libp2p_port: u16,
     _libp2p_exit: oneshot::Sender<()>,
     _network_send: mpsc::UnboundedSender<NetworkMessage>,
     _phantom: PhantomData<T>, //message_handler: MessageHandler,
@@ -56,6 +57,7 @@ impl<T: BeaconChainTypes + 'static> Service<T> {
         )?;
         let network_service = Service {
             libp2p_service,
+            libp2p_port: config.libp2p_port,
             _libp2p_exit: libp2p_exit,
             _network_send: network_send.clone(),
             _phantom: PhantomData,
@@ -64,6 +66,52 @@ impl<T: BeaconChainTypes + 'static> Service<T> {
         Ok((Arc::new(network_service), network_send))
     }
 
+    /// Returns the local ENR from the underlying Discv5 behaviour that external peers may connect
+    /// to.
+    pub fn local_enr(&self) -> Enr {
+        self.libp2p_service
+            .lock()
+            .swarm
+            .discovery()
+            .local_enr()
+            .clone()
+    }
+
+    /// Returns the local libp2p PeerID.
+    pub fn local_peer_id(&self) -> PeerId {
+        self.libp2p_service.lock().local_peer_id.clone()
+    }
+
+    /// Returns the list of `Multiaddr` that the underlying libp2p instance is listening on.
+    pub fn listen_multiaddrs(&self) -> Vec<Multiaddr> {
+        Swarm::listeners(&self.libp2p_service.lock().swarm)
+            .cloned()
+            .collect()
+    }
+
+    /// Returns the libp2p port that this node has been configured to listen using.
+    pub fn listen_port(&self) -> u16 {
+        self.libp2p_port
+    }
+
+    /// Returns the number of libp2p connected peers.
+    pub fn connected_peers(&self) -> usize {
+        self.libp2p_service.lock().swarm.connected_peers()
+    }
+
+    /// Returns the set of `PeerId` that are connected via libp2p.
+    pub fn connected_peer_set(&self) -> Vec<PeerId> {
+        self.libp2p_service
+            .lock()
+            .swarm
+            .discovery()
+            .connected_peer_set()
+            .iter()
+            .cloned()
+            .collect()
+    }
+
+    /// Provides a reference to the underlying libp2p service.
     pub fn libp2p_service(&self) -> Arc<Mutex<LibP2PService>> {
         self.libp2p_service.clone()
     }

beacon_node/rest_api/Cargo.toml

@@ -7,6 +7,8 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 [dependencies]
 beacon_chain = { path = "../beacon_chain" }
+network = { path = "../network" }
+eth2-libp2p = { path = "../eth2-libp2p" }
 store = { path = "../store" }
 version = { path = "../version" }
 serde = { version = "1.0", features = ["derive"] }

beacon_node/rest_api/src/beacon.rs

@@ -2,9 +2,114 @@ use super::{success_response, ApiResult};
 use crate::{helpers::*, ApiError, UrlQuery};
 use beacon_chain::{BeaconChain, BeaconChainTypes};
 use hyper::{Body, Request};
+use serde::Serialize;
 use std::sync::Arc;
 use store::Store;
-use types::BeaconState;
+use types::{BeaconBlock, BeaconState, EthSpec, Hash256, Slot};
+
+#[derive(Serialize)]
+pub struct HeadResponse {
+    pub slot: Slot,
+    pub block_root: Hash256,
+    pub state_root: Hash256,
+}
+
+/// HTTP handler to return a `BeaconBlock` at a given `root` or `slot`.
+pub fn get_head<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiResult {
+    let beacon_chain = req
+        .extensions()
+        .get::<Arc<BeaconChain<T>>>()
+        .ok_or_else(|| ApiError::ServerError("Beacon chain extension missing".to_string()))?;
+
+    let head = HeadResponse {
+        slot: beacon_chain.head().beacon_state.slot,
+        block_root: beacon_chain.head().beacon_block_root,
+        state_root: beacon_chain.head().beacon_state_root,
+    };
+
+    let json: String = serde_json::to_string(&head)
+        .map_err(|e| ApiError::ServerError(format!("Unable to serialize HeadResponse: {:?}", e)))?;
+
+    Ok(success_response(Body::from(json)))
+}
+
+#[derive(Serialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct BlockResponse<T: EthSpec> {
+    pub root: Hash256,
+    pub beacon_block: BeaconBlock<T>,
+}
+
+/// HTTP handler to return a `BeaconBlock` at a given `root` or `slot`.
+pub fn get_block<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiResult {
+    let beacon_chain = req
+        .extensions()
+        .get::<Arc<BeaconChain<T>>>()
+        .ok_or_else(|| ApiError::ServerError("Beacon chain extension missing".to_string()))?;
+
+    let query_params = ["root", "slot"];
+    let (key, value) = UrlQuery::from_request(&req)?.first_of(&query_params)?;
+
+    let block_root = match (key.as_ref(), value) {
+        ("slot", value) => {
+            let target = parse_slot(&value)?;
+
+            block_root_at_slot(&beacon_chain, target).ok_or_else(|| {
+                ApiError::NotFound(format!("Unable to find BeaconBlock for slot {}", target))
+            })?
+        }
+        ("root", value) => parse_root(&value)?,
+        _ => return Err(ApiError::ServerError("Unexpected query parameter".into())),
+    };
+
+    let block = beacon_chain
+        .store
+        .get::<BeaconBlock<T::EthSpec>>(&block_root)?
+        .ok_or_else(|| {
+            ApiError::NotFound(format!(
+                "Unable to find BeaconBlock for root {}",
+                block_root
+            ))
+        })?;
+
+    let response = BlockResponse {
+        root: block_root,
+        beacon_block: block,
+    };
+
+    let json: String = serde_json::to_string(&response).map_err(|e| {
+        ApiError::ServerError(format!("Unable to serialize BlockResponse: {:?}", e))
+    })?;
+
+    Ok(success_response(Body::from(json)))
+}
+
+/// HTTP handler to return a `BeaconBlock` root at a given `slot`.
+pub fn get_block_root<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiResult {
+    let beacon_chain = req
+        .extensions()
+        .get::<Arc<BeaconChain<T>>>()
+        .ok_or_else(|| ApiError::ServerError("Beacon chain extension missing".to_string()))?;
+
+    let slot_string = UrlQuery::from_request(&req)?.only_one("slot")?;
+    let target = parse_slot(&slot_string)?;
+
+    let root = block_root_at_slot(&beacon_chain, target).ok_or_else(|| {
+        ApiError::NotFound(format!("Unable to find BeaconBlock for slot {}", target))
+    })?;
+
+    let json: String = serde_json::to_string(&root)
+        .map_err(|e| ApiError::ServerError(format!("Unable to serialize root: {:?}", e)))?;
+
+    Ok(success_response(Body::from(json)))
+}
+
+#[derive(Serialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct StateResponse<T: EthSpec> {
+    pub root: Hash256,
+    pub beacon_state: BeaconState<T>,
+}
 
 /// HTTP handler to return a `BeaconState` at a given `root` or `slot`.
 ///
@@ -19,26 +124,34 @@ pub fn get_state<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiResult
     let query_params = ["root", "slot"];
     let (key, value) = UrlQuery::from_request(&req)?.first_of(&query_params)?;
 
-    let state: BeaconState<T::EthSpec> = match (key.as_ref(), value) {
+    let (root, state): (Hash256, BeaconState<T::EthSpec>) = match (key.as_ref(), value) {
         ("slot", value) => state_at_slot(&beacon_chain, parse_slot(&value)?)?,
         ("root", value) => {
             let root = &parse_root(&value)?;
 
-            beacon_chain
+            let state = beacon_chain
                 .store
                 .get(root)?
-                .ok_or_else(|| ApiError::NotFound(format!("No state for root: {}", root)))?
+                .ok_or_else(|| ApiError::NotFound(format!("No state for root: {}", root)))?;
+
+            (*root, state)
         }
-        _ => unreachable!("Guarded by UrlQuery::from_request()"),
+        _ => return Err(ApiError::ServerError("Unexpected query parameter".into())),
     };
 
-    let json: String = serde_json::to_string(&state)
+    let response = StateResponse {
-        .map_err(|e| ApiError::ServerError(format!("Unable to serialize BeaconState: {:?}", e)))?;
+        root,
+        beacon_state: state,
+    };
+
+    let json: String = serde_json::to_string(&response).map_err(|e| {
+        ApiError::ServerError(format!("Unable to serialize StateResponse: {:?}", e))
+    })?;
 
     Ok(success_response(Body::from(json)))
 }
 
-/// HTTP handler to return a `BeaconState` root at a given or `slot`.
+/// HTTP handler to return a `BeaconState` root at a given `slot`.
 ///
 /// Will not return a state if the request slot is in the future. Will return states higher than
 /// the current head by skipping slots.
@@ -58,3 +171,24 @@ pub fn get_state_root<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiR
 
     Ok(success_response(Body::from(json)))
 }
+
+/// HTTP handler to return the highest finalized slot.
+pub fn get_latest_finalized_checkpoint<T: BeaconChainTypes + 'static>(
+    req: Request<Body>,
+) -> ApiResult {
+    let beacon_chain = req
+        .extensions()
+        .get::<Arc<BeaconChain<T>>>()
+        .ok_or_else(|| ApiError::ServerError("Beacon chain extension missing".to_string()))?;
+
+    let checkpoint = beacon_chain
+        .head()
+        .beacon_state
+        .finalized_checkpoint
+        .clone();
+
+    let json: String = serde_json::to_string(&checkpoint)
+        .map_err(|e| ApiError::ServerError(format!("Unable to serialize checkpoint: {:?}", e)))?;
+
+    Ok(success_response(Body::from(json)))
+}

beacon_node/rest_api/src/helpers.rs

@@ -31,22 +31,40 @@ pub fn parse_root(string: &str) -> Result<Hash256, ApiError> {
     }
 }
 
-/// Returns a `BeaconState` in the canonical chain of `beacon_chain` at the given `slot`, if
+/// Returns the root of the `BeaconBlock` in the canonical chain of `beacon_chain` at the given
-/// possible.
+/// `slot`, if possible.
+///
+/// May return a root for a previous slot, in the case of skip slots.
+pub fn block_root_at_slot<T: BeaconChainTypes>(
+    beacon_chain: &BeaconChain<T>,
+    target: Slot,
+) -> Option<Hash256> {
+    beacon_chain
+        .rev_iter_block_roots()
+        .take_while(|(_root, slot)| *slot >= target)
+        .find(|(_root, slot)| *slot == target)
+        .map(|(root, _slot)| root)
+}
+
+/// Returns a `BeaconState` and it's root in the canonical chain of `beacon_chain` at the given
+/// `slot`, if possible.
 ///
 /// Will not return a state if the request slot is in the future. Will return states higher than
 /// the current head by skipping slots.
 pub fn state_at_slot<T: BeaconChainTypes>(
     beacon_chain: &BeaconChain<T>,
     slot: Slot,
-) -> Result<BeaconState<T::EthSpec>, ApiError> {
+) -> Result<(Hash256, BeaconState<T::EthSpec>), ApiError> {
     let head_state = &beacon_chain.head().beacon_state;
 
     if head_state.slot == slot {
         // The request slot is the same as the best block (head) slot.
 
         // I'm not sure if this `.clone()` will be optimized out. If not, it seems unnecessary.
-        Ok(beacon_chain.head().beacon_state.clone())
+        Ok((
+            beacon_chain.head().beacon_state_root,
+            beacon_chain.head().beacon_state.clone(),
+        ))
     } else {
         let root = state_root_at_slot(beacon_chain, slot)?;
 
@@ -55,7 +73,7 @@ pub fn state_at_slot<T: BeaconChainTypes>(
             .get(&root)?
             .ok_or_else(|| ApiError::NotFound(format!("Unable to find state at root {}", root)))?;
 
-        Ok(state)
+        Ok((root, state))
     }
 }
 

beacon_node/rest_api/src/lib.rs

@@ -1,15 +1,18 @@
 #[macro_use]
 extern crate lazy_static;
+extern crate network as client_network;
 
 mod beacon;
 mod config;
 mod helpers;
 mod metrics;
+mod network;
 mod node;
+mod spec;
 mod url_query;
 
 use beacon_chain::{BeaconChain, BeaconChainTypes};
-pub use config::Config as ApiConfig;
+use client_network::Service as NetworkService;
 use hyper::rt::Future;
 use hyper::service::service_fn_ok;
 use hyper::{Body, Method, Response, Server, StatusCode};
@@ -20,6 +23,9 @@ use std::sync::Arc;
 use tokio::runtime::TaskExecutor;
 use url_query::UrlQuery;
 
+pub use beacon::{BlockResponse, HeadResponse, StateResponse};
+pub use config::Config as ApiConfig;
+
 #[derive(PartialEq, Debug)]
 pub enum ApiError {
     MethodNotAllowed(String),
@@ -67,10 +73,11 @@ impl From<state_processing::per_slot_processing::Error> for ApiError {
     }
 }
 
-pub fn start_server<T: BeaconChainTypes + Clone + 'static>(
+pub fn start_server<T: BeaconChainTypes>(
     config: &ApiConfig,
     executor: &TaskExecutor,
     beacon_chain: Arc<BeaconChain<T>>,
+    network_service: Arc<NetworkService<T>>,
     db_path: PathBuf,
     log: &slog::Logger,
 ) -> Result<exit_future::Signal, hyper::Error> {
@@ -98,6 +105,7 @@ pub fn start_server<T: BeaconChainTypes + Clone + 'static>(
         let log = server_log.clone();
         let beacon_chain = server_bc.clone();
         let db_path = db_path.clone();
+        let network_service = network_service.clone();
 
         // Create a simple handler for the router, inject our stateful objects into the request.
         service_fn_ok(move |mut req| {
@@ -108,16 +116,34 @@ pub fn start_server<T: BeaconChainTypes + Clone + 'static>(
             req.extensions_mut()
                 .insert::<Arc<BeaconChain<T>>>(beacon_chain.clone());
             req.extensions_mut().insert::<DBPath>(db_path.clone());
+            req.extensions_mut()
+                .insert::<Arc<NetworkService<T>>>(network_service.clone());
 
             let path = req.uri().path().to_string();
 
             // Route the request to the correct handler.
             let result = match (req.method(), path.as_ref()) {
+                (&Method::GET, "/beacon/head") => beacon::get_head::<T>(req),
+                (&Method::GET, "/beacon/block") => beacon::get_block::<T>(req),
+                (&Method::GET, "/beacon/block_root") => beacon::get_block_root::<T>(req),
+                (&Method::GET, "/beacon/latest_finalized_checkpoint") => {
+                    beacon::get_latest_finalized_checkpoint::<T>(req)
+                }
                 (&Method::GET, "/beacon/state") => beacon::get_state::<T>(req),
                 (&Method::GET, "/beacon/state_root") => beacon::get_state_root::<T>(req),
                 (&Method::GET, "/metrics") => metrics::get_prometheus::<T>(req),
+                (&Method::GET, "/network/enr") => network::get_enr::<T>(req),
+                (&Method::GET, "/network/peer_count") => network::get_peer_count::<T>(req),
+                (&Method::GET, "/network/peer_id") => network::get_peer_id::<T>(req),
+                (&Method::GET, "/network/peers") => network::get_peer_list::<T>(req),
+                (&Method::GET, "/network/listen_port") => network::get_listen_port::<T>(req),
+                (&Method::GET, "/network/listen_addresses") => {
+                    network::get_listen_addresses::<T>(req)
+                }
                 (&Method::GET, "/node/version") => node::get_version(req),
                 (&Method::GET, "/node/genesis_time") => node::get_genesis_time::<T>(req),
+                (&Method::GET, "/spec") => spec::get_spec::<T>(req),
+                (&Method::GET, "/spec/slots_per_epoch") => spec::get_slots_per_epoch::<T>(req),
                 _ => Err(ApiError::MethodNotAllowed(path.clone())),
             };
 

beacon_node/rest_api/src/network.rs

@@ -0,0 +1,108 @@
+use crate::{success_response, ApiError, ApiResult, NetworkService};
+use beacon_chain::BeaconChainTypes;
+use eth2_libp2p::{Enr, Multiaddr, PeerId};
+use hyper::{Body, Request};
+use std::sync::Arc;
+
+/// HTTP handle to return the list of libp2p multiaddr the client is listening on.
+///
+/// Returns a list of `Multiaddr`, serialized according to their `serde` impl.
+pub fn get_listen_addresses<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    let multiaddresses: Vec<Multiaddr> = network.listen_multiaddrs();
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&multiaddresses)
+            .map_err(|e| ApiError::ServerError(format!("Unable to serialize Enr: {:?}", e)))?,
+    )))
+}
+
+/// HTTP handle to return the list of libp2p multiaddr the client is listening on.
+///
+/// Returns a list of `Multiaddr`, serialized according to their `serde` impl.
+pub fn get_listen_port<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&network.listen_port())
+            .map_err(|e| ApiError::ServerError(format!("Unable to serialize port: {:?}", e)))?,
+    )))
+}
+
+/// HTTP handle to return the Discv5 ENR from the client's libp2p service.
+///
+/// ENR is encoded as base64 string.
+pub fn get_enr<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    let enr: Enr = network.local_enr();
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&enr.to_base64())
+            .map_err(|e| ApiError::ServerError(format!("Unable to serialize Enr: {:?}", e)))?,
+    )))
+}
+
+/// HTTP handle to return the `PeerId` from the client's libp2p service.
+///
+/// PeerId is encoded as base58 string.
+pub fn get_peer_id<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    let peer_id: PeerId = network.local_peer_id();
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&peer_id.to_base58())
+            .map_err(|e| ApiError::ServerError(format!("Unable to serialize Enr: {:?}", e)))?,
+    )))
+}
+
+/// HTTP handle to return the number of peers connected in the client's libp2p service.
+pub fn get_peer_count<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    let connected_peers: usize = network.connected_peers();
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&connected_peers)
+            .map_err(|e| ApiError::ServerError(format!("Unable to serialize Enr: {:?}", e)))?,
+    )))
+}
+
+/// HTTP handle to return the list of peers connected to the client's libp2p service.
+///
+/// Peers are presented as a list of `PeerId::to_string()`.
+pub fn get_peer_list<T: BeaconChainTypes>(req: Request<Body>) -> ApiResult {
+    let network = req
+        .extensions()
+        .get::<Arc<NetworkService<T>>>()
+        .ok_or_else(|| ApiError::ServerError("NetworkService extension missing".to_string()))?;
+
+    let connected_peers: Vec<String> = network
+        .connected_peer_set()
+        .iter()
+        .map(PeerId::to_string)
+        .collect();
+
+    Ok(success_response(Body::from(
+        serde_json::to_string(&connected_peers).map_err(|e| {
+            ApiError::ServerError(format!("Unable to serialize Vec<PeerId>: {:?}", e))
+        })?,
+    )))
+}

beacon_node/rest_api/src/spec.rs

@@ -0,0 +1,27 @@
+use super::{success_response, ApiResult};
+use crate::ApiError;
+use beacon_chain::{BeaconChain, BeaconChainTypes};
+use hyper::{Body, Request};
+use std::sync::Arc;
+use types::EthSpec;
+
+/// HTTP handler to return the full spec object.
+pub fn get_spec<T: BeaconChainTypes + 'static>(req: Request<Body>) -> ApiResult {
+    let beacon_chain = req
+        .extensions()
+        .get::<Arc<BeaconChain<T>>>()
+        .ok_or_else(|| ApiError::ServerError("Beacon chain extension missing".to_string()))?;
+
+    let json: String = serde_json::to_string(&beacon_chain.spec)
+        .map_err(|e| ApiError::ServerError(format!("Unable to serialize spec: {:?}", e)))?;
+
+    Ok(success_response(Body::from(json)))
+}
+
+/// HTTP handler to return the full spec object.
+pub fn get_slots_per_epoch<T: BeaconChainTypes + 'static>(_req: Request<Body>) -> ApiResult {
+    let json: String = serde_json::to_string(&T::EthSpec::slots_per_epoch())
+        .map_err(|e| ApiError::ServerError(format!("Unable to serialize epoch: {:?}", e)))?;
+
+    Ok(success_response(Body::from(json)))
+}

beacon_node/src/main.rs

@@ -200,6 +200,16 @@ fn main() {
                 .help("Sets the verbosity level")
                 .takes_value(true),
         )
+        /*
+         * Bootstrap.
+         */
+        .arg(
+            Arg::with_name("bootstrap")
+                .long("bootstrap")
+                .value_name("HTTP_SERVER")
+                .help("Load the genesis state and libp2p address from the HTTP API of another Lighthouse node.")
+                .takes_value(true)
+        )
         .get_matches();
 
     // build the initial logger
@@ -227,6 +237,11 @@ fn main() {
 
     let mut log = slog::Logger::root(drain.fuse(), o!());
 
+    warn!(
+        log,
+        "Ethereum 2.0 is pre-release. This software is experimental."
+    );
+
     let data_dir = match matches
         .value_of("datadir")
         .and_then(|v| Some(PathBuf::from(v)))

beacon_node/src/run.rs

@@ -4,7 +4,7 @@ use client::{
 };
 use futures::sync::oneshot;
 use futures::Future;
-use slog::{error, info, warn};
+use slog::{error, info};
 use std::cell::RefCell;
 use std::path::Path;
 use std::path::PathBuf;
@@ -42,11 +42,6 @@ pub fn run_beacon_node(
 
     let other_client_config = client_config.clone();
 
-    warn!(
-        log,
-        "Ethereum 2.0 is pre-release. This software is experimental."
-    );
-
     info!(
         log,
         "BeaconNode init";
@@ -123,7 +118,7 @@ fn run<T>(
     log: &slog::Logger,
 ) -> error::Result<()>
 where
-    T: BeaconChainTypes + InitialiseBeaconChain<T> + Clone + Send + Sync + 'static,
+    T: BeaconChainTypes + InitialiseBeaconChain<T> + Clone,
     T::Store: OpenDatabase,
 {
     let store = T::Store::open_database(&db_path)?;

eth2/types/src/beacon_block_body.rs

@@ -1,5 +1,5 @@
 use crate::test_utils::TestRandom;
-use crate::utils::graffiti_from_hex_str;
+use crate::utils::{graffiti_from_hex_str, graffiti_to_hex_str};
 use crate::*;
 
 use serde_derive::{Deserialize, Serialize};
@@ -16,7 +16,10 @@ use tree_hash_derive::TreeHash;
 pub struct BeaconBlockBody<T: EthSpec> {
     pub randao_reveal: Signature,
     pub eth1_data: Eth1Data,
-    #[serde(deserialize_with = "graffiti_from_hex_str")]
+    #[serde(
+        serialize_with = "graffiti_to_hex_str",
+        deserialize_with = "graffiti_from_hex_str"
+    )]
     pub graffiti: [u8; 32],
     pub proposer_slashings: VariableList<ProposerSlashing, T::MaxProposerSlashings>,
     pub attester_slashings: VariableList<AttesterSlashing<T>, T::MaxAttesterSlashings>,

eth2/types/src/utils/serde_utils.rs

@@ -46,8 +46,20 @@ where
     Ok(array)
 }
 
-// #[allow(clippy::trivially_copy_pass_by_ref)] // Serde requires the `byte` to be a ref.
+pub fn fork_to_hex_str<S>(bytes: &[u8; FORK_BYTES_LEN], serializer: S) -> Result<S::Ok, S::Error>
-pub fn fork_to_hex_str<S>(bytes: &[u8; 4], serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    let mut hex_string: String = "0x".to_string();
+    hex_string.push_str(&hex::encode(&bytes));
+
+    serializer.serialize_str(&hex_string)
+}
+
+pub fn graffiti_to_hex_str<S>(
+    bytes: &[u8; GRAFFITI_BYTES_LEN],
+    serializer: S,
+) -> Result<S::Ok, S::Error>
 where
     S: Serializer,
 {