Eth1 Integration (#542)

* Refactor to cache Eth1Data * Fix merge conflicts and minor refactorings * Rename Eth1Cache to Eth1DataCache * Refactor events subscription * Add deposits module to interface with BeaconChain deposits * Remove utils * Rename to types.rs and add trait constraints to Eth1DataFetcher * Confirm to trait constraints. Make Web3DataFetcher cloneable * Make fetcher object member of deposit and eth1_data cache and other fixes * Fix update_cache function * Move fetch_eth1_data to impl block * Fix deposit tests * Create Eth1 object for interfacing with Beacon chain * Add `run` function for running update_cache and subscribe_deposit_logs tasks * Add logging * Run `cargo fmt` and make tests pass * Convert sync functions to async * Add timeouts to web3 functions * Return futures from cache functions * Add failed chaining of futures * Working cache updation * Clean up tests and `update_cache` function * Refactor `get_eth1_data` functions to work with future returning functions * Refactor eth1 `run` function to work with modified `update_cache` api * Minor changes * Add distance parameter to `update_cache` * Fix tests and other minor fixes * Working integration with cache and deposits * Add merkle_tree construction, proof generation and verification code * Add function to construct and fetch Deposits for BeaconNode * Add error handling * Import ssz * Add error handling to eth1 cache and fix minor errors * Run rustfmt * Fix minor bug * Rename Eth1Error and change to Result<T> * Change deposit fetching mechanism from notification based to poll based * Add deposits from eth1 chain in a given range every `x` blocks * Modify `run` function to accommodate changes * Minor fixes * Fix formatting * Initial commit. web3 api working. * Tidied up lib. Add function for fetching logs. * Refactor with `Eth1DataFetcher` trait * Add parsing for deposit contract logs and get_eth1_data function * Add `get_eth1_votes` function * Refactor to cache Eth1Data * Fix merge conflicts and minor refactorings * Rename Eth1Cache to Eth1DataCache * Refactor events subscription * Add deposits module to interface with BeaconChain deposits * Remove utils * Rename to types.rs and add trait constraints to Eth1DataFetcher * Confirm to trait constraints. Make Web3DataFetcher cloneable * Make fetcher object member of deposit and eth1_data cache and other fixes * Fix update_cache function * Move fetch_eth1_data to impl block * Fix deposit tests * Create Eth1 object for interfacing with Beacon chain * Add `run` function for running update_cache and subscribe_deposit_logs tasks * Add logging * Run `cargo fmt` and make tests pass * Convert sync functions to async * Add timeouts to web3 functions * Return futures from cache functions * Add failed chaining of futures * Working cache updation * Clean up tests and `update_cache` function * Refactor `get_eth1_data` functions to work with future returning functions * Refactor eth1 `run` function to work with modified `update_cache` api * Minor changes * Add distance parameter to `update_cache` * Fix tests and other minor fixes * Working integration with cache and deposits * Add merkle_tree construction, proof generation and verification code * Add function to construct and fetch Deposits for BeaconNode * Add error handling * Import ssz * Add error handling to eth1 cache and fix minor errors * Run rustfmt * Fix minor bug * Rename Eth1Error and change to Result<T> * Change deposit fetching mechanism from notification based to poll based * Add deposits from eth1 chain in a given range every `x` blocks * Modify `run` function to accommodate changes * Minor fixes * Fix formatting * Fix merge issue * Refactor with `Config` struct. Remote `ContractConfig` * Rename eth1_chain crate to eth1 * Rename files and read abi file using `fs::read` * Move eth1 to lib * Remove unnecessary mutability constraint * Add `Web3Backend` for returning actual eth1 data * Refactor `get_eth1_votes` to return a Result * Delete `eth1_chain` crate * Return `Result` from `get_deposits` * Fix range of deposits to return to beacon chain * Add `get_block_height_by_hash` trait function * Add naive method for getting `previous_eth1_distance` * Add eth1 config params to main config * Add instructions for setting up eth1 testing environment * Add build script to fetch deposit contract abi * Contract ABI is part of compiled binary * Fix minor bugs * Move docs to lib * Add timeout to config * Remove print statements * Change warn to error * Fix typos * Removed prints in test and get timeout value from config * Fixed error types * Added logging to web3_fetcher * Refactor for modified web3 api * Fix minor stuff * Add build script * Tidy, hide eth1 integration tests behind flag * Add http crate * Add first stages of eth1_test_rig * Fix deposits on test rig * Fix bug with deposit count method * Add block hash getter to http eth1 * Clean eth1 http crate and tests * Add script to start ganache * Adds deposit tree to eth1-http * Extend deposit tree tests * Tidy tests in eth1-http * Add more detail to get block request * Add block cache to eth1-http * Rename deposit tree to deposit cache * Add inital updating to eth1-http * Tidy updater * Fix compile bugs in tests * Adds an Eth1DataCache builder * Reorg eth1-http files * Add (failing) tests for eth1 updater * Rename files, fix bug in eth1-http * Ensure that ganache timestamps are increasing * Fix bugs with getting eth1data ancestors * Improve eth1 testing, fix bugs * Add truncate method to block cache * Add pruning to block cache update process * Add tests for block pruning * Allow for dropping an expired cache. * Add more comments * Add first compiling version of deposit updater * Add common fn for getting range of required blocks * Add passing deposit update test * Improve tests * Fix block pruning bug * Add tests for running two updates at once * Add updater services to eth1 * Add deposit collection to beacon chain * Add incomplete builder experiments * Add first working version of beacon chain builder * Update test harness to new beacon chain type * Rename builder file, tidy * Add first working client builder * Progress further on client builder * Update becaon node binary to use client builder * Ensure release tests compile * Remove old eth1 crate * Add first pass of new lighthouse binary * Fix websocket server startup * Remove old binary code from beacon_node crate * Add first working beacon node tests * Add genesis crate, new eth1 cache_2 * Add Serivce to Eth1Cache * Refactor with general eth1 improvements * Add passing genesis test * Tidy, add comments * Add more comments to eth1 service * Add further eth1 progress * Fix some bugs with genesis * Fix eth1 bugs, make eth1 linking more efficient * Shift logic in genesis service * Add more comments to genesis service * Add gzip, max request values, timeouts to http * Update testnet parameters to suit goerli testnet * Add ability to vary Fork, fix custom spec * Be more explicit about deposit fork version * Start adding beacon chain eth1 option * Add more flexibility to prod client * Further runtime refactoring * Allow for starting from store * Add bootstrapping to client config * Add remote_beacon_node crate * Update eth1 service for more configurability * Update eth1 tests to use less runtimes * Patch issues with tests using too many files * Move dummy eth1 backend flag * Ensure all tests pass * Add ganache-cli to Dockerfile * Use a special docker hub image for testing * Appease clippy * Move validator client into lighthouse binary * Allow starting with dummy eth1 backend * Improve logging * Fix dummy eth1 backend from cli * Add extra testnet command * Ensure consistent spec in beacon node * Update eth1 rig to work on goerli * Tidy lcli, start adding support for yaml config * Add incomplete YamlConfig struct * Remove efforts at YamlConfig * Add incomplete eth1 voting. Blocked on spec issues * Add (untested) first pass at eth1 vote algo * Add tests for winning vote * Add more tests for eth1 chain * Add more eth1 voting tests * Added more eth1 voting testing * Change test name * Add more tests to eth1 chain * Tidy eth1 generics, add more tests * Improve comments * Tidy beacon_node tests * Tidy, rename JsonRpc.. to Caching.. * Tidy voting logic * Tidy builder docs * Add comments, tidy eth1 * Add more comments to eth1 * Fix bug with winning_vote * Add doc comments to the `ClientBuilder` * Remove commented-out code * Improve `ClientBuilder` docs * Add comments to client config * Add decoding test for `ClientConfig` * Remove unused `DepositSet` struct * Tidy `block_cache` * Remove commented out lines * Remove unused code in `eth1` crate * Remove old validator binary `main.rs` * Tidy, fix tests compile error * Add initial tests for get_deposits * Remove dead code in eth1_test_rig * Update TestingDepositBuilder * Add testing for getting eth1 deposits * Fix duplicate rand dep * Remove dead code * Remove accidentally-added files * Fix comment in eth1_genesis_service * Add .gitignore for eth1_test_rig * Fix bug in eth1_genesis_service * Remove dead code from eth2_config * Fix tabs/spaces in root Cargo.toml * Tidy eth1 crate * Allow for re-use of eth1 service after genesis * Update docs for new CLI * Change README gif * Tidy eth1 http module * Tidy eth1 service * Tidy environment crate * Remove unused file * Tidy, add comments * Remove commented-out code * Address majority of Michael's comments * Address other PR comments * Add link to issue alongside TODO
2019-11-15 14:47:51 +11:00
parent 97729f8654
commit f229bbba1c
99 changed files with 8263 additions and 1631 deletions
@@ -5,7 +5,7 @@ extern crate lazy_static;

 use beacon_chain::test_utils::{
    generate_deterministic_keypairs, AttestationStrategy,
-    BeaconChainHarness as BaseBeaconChainHarness, BlockStrategy,
+    BeaconChainHarness as BaseBeaconChainHarness, BlockStrategy, HarnessType,
 };
 use lmd_ghost::{LmdGhost, ThreadSafeReducedTree as BaseThreadSafeReducedTree};
 use rand::{prelude::*, rngs::StdRng};
@@ -21,7 +21,7 @@ pub const VALIDATOR_COUNT: usize = 3 * 8;

 type TestEthSpec = MinimalEthSpec;
 type ThreadSafeReducedTree = BaseThreadSafeReducedTree<MemoryStore, TestEthSpec>;
-type BeaconChainHarness = BaseBeaconChainHarness<ThreadSafeReducedTree, TestEthSpec>;
+type BeaconChainHarness = BaseBeaconChainHarness<HarnessType<TestEthSpec>>;
 type RootAndSlot = (Hash256, Slot);

 lazy_static! {
@@ -52,7 +52,10 @@ struct ForkedHarness {
 impl ForkedHarness {
    /// A new standard instance of with constant parameters.
    pub fn new() -> Self {
-        let harness = BeaconChainHarness::new(generate_deterministic_keypairs(VALIDATOR_COUNT));
+        let harness = BeaconChainHarness::new(
+            MinimalEthSpec,
+            generate_deterministic_keypairs(VALIDATOR_COUNT),
+        );

        // Move past the zero slot.
        harness.advance_slot();
@@ -598,7 +598,7 @@ mod tests {

        let mut state = BeaconState::random_for_test(rng);

-        state.fork = Fork::genesis(MainnetEthSpec::genesis_epoch());
+        state.fork = Fork::default();

        (spec, state)
    }
@@ -35,18 +35,7 @@ pub fn initialize_beacon_state_from_eth1<T: EthSpec>(
        process_deposit(&mut state, &deposit, spec, true)?;
    }

-    // Process activations
-    for (index, validator) in state.validators.iter_mut().enumerate() {
-        let balance = state.balances[index];
-        validator.effective_balance = std::cmp::min(
-            balance - balance % spec.effective_balance_increment,
-            spec.max_effective_balance,
-        );
-        if validator.effective_balance == spec.max_effective_balance {
-            validator.activation_eligibility_epoch = T::genesis_epoch();
-            validator.activation_epoch = T::genesis_epoch();
-        }
-    }
+    process_activations(&mut state, spec);

    // Now that we have our validators, initialize the caches (including the committees)
    state.build_all_caches(spec)?;
@@ -71,3 +60,20 @@ pub fn is_valid_genesis_state<T: EthSpec>(state: &BeaconState<T>, spec: &ChainSp
        && state.get_active_validator_indices(T::genesis_epoch()).len() as u64
            >= spec.min_genesis_active_validator_count
 }
+
+/// Activate genesis validators, if their balance is acceptable.
+///
+/// Spec v0.8.0
+pub fn process_activations<T: EthSpec>(state: &mut BeaconState<T>, spec: &ChainSpec) {
+    for (index, validator) in state.validators.iter_mut().enumerate() {
+        let balance = state.balances[index];
+        validator.effective_balance = std::cmp::min(
+            balance - balance % spec.effective_balance_increment,
+            spec.max_effective_balance,
+        );
+        if validator.effective_balance == spec.max_effective_balance {
+            validator.activation_eligibility_epoch = T::genesis_epoch();
+            validator.activation_epoch = T::genesis_epoch();
+        }
+    }
+}
@@ -8,7 +8,7 @@ pub mod per_epoch_processing;
 pub mod per_slot_processing;
 pub mod test_utils;

-pub use genesis::{initialize_beacon_state_from_eth1, is_valid_genesis_state};
+pub use genesis::{initialize_beacon_state_from_eth1, is_valid_genesis_state, process_activations};
 pub use per_block_processing::{
    errors::BlockProcessingError, per_block_processing, BlockSignatureStrategy, VerifySignatures,
 };
@@ -444,7 +444,7 @@ pub fn process_deposit<T: EthSpec>(
    } else {
        // The signature should be checked for new validators. Return early for a bad
        // signature.
-        if verify_deposit_signature(state, deposit, spec).is_err() {
+        if verify_deposit_signature(&deposit.data, spec).is_err() {
            return Ok(());
        }

@@ -7,7 +7,7 @@ use std::convert::TryInto;
 use tree_hash::{SignedRoot, TreeHash};
 use types::{
    AggregateSignature, AttestationDataAndCustodyBit, AttesterSlashing, BeaconBlock,
-    BeaconBlockHeader, BeaconState, BeaconStateError, ChainSpec, Deposit, Domain, EthSpec, Fork,
+    BeaconBlockHeader, BeaconState, BeaconStateError, ChainSpec, DepositData, Domain, EthSpec,
    Hash256, IndexedAttestation, ProposerSlashing, PublicKey, RelativeEpoch, Signature, Transfer,
    VoluntaryExit,
 };
@@ -194,18 +194,17 @@ pub fn attester_slashing_signature_sets<'a, T: EthSpec>(
 ///
 /// This method is separate to `deposit_signature_set` to satisfy lifetime requirements.
 pub fn deposit_pubkey_signature_message(
-    deposit: &Deposit,
+    deposit_data: &DepositData,
 ) -> Option<(PublicKey, Signature, Vec<u8>)> {
-    let pubkey = (&deposit.data.pubkey).try_into().ok()?;
-    let signature = (&deposit.data.signature).try_into().ok()?;
-    let message = deposit.data.signed_root();
+    let pubkey = (&deposit_data.pubkey).try_into().ok()?;
+    let signature = (&deposit_data.signature).try_into().ok()?;
+    let message = deposit_data.signed_root();
    Some((pubkey, signature, message))
 }

 /// Returns the signature set for some set of deposit signatures, made with
 /// `deposit_pubkey_signature_message`.
-pub fn deposit_signature_set<'a, T: EthSpec>(
-    state: &'a BeaconState<T>,
+pub fn deposit_signature_set<'a>(
    pubkey_signature_message: &'a (PublicKey, Signature, Vec<u8>),
    spec: &'a ChainSpec,
 ) -> SignatureSet<'a> {
@@ -213,9 +212,12 @@ pub fn deposit_signature_set<'a, T: EthSpec>(

    // Note: Deposits are valid across forks, thus the deposit domain is computed
    // with the fork zeroed.
-    let domain = spec.get_domain(state.current_epoch(), Domain::Deposit, &Fork::default());
-
-    SignatureSet::single(signature, pubkey, message.clone(), domain)
+    SignatureSet::single(
+        signature,
+        pubkey,
+        message.clone(),
+        spec.get_deposit_domain(),
+    )
 }

 /// Returns a signature set that is valid if the `VoluntaryExit` was signed by the indicated
@@ -15,16 +15,12 @@ fn error(reason: DepositInvalid) -> BlockOperationError<DepositInvalid> {
 /// Verify `Deposit.pubkey` signed `Deposit.signature`.
 ///
 /// Spec v0.8.0
-pub fn verify_deposit_signature<T: EthSpec>(
-    state: &BeaconState<T>,
-    deposit: &Deposit,
-    spec: &ChainSpec,
-) -> Result<()> {
-    let deposit_signature_message = deposit_pubkey_signature_message(deposit)
+pub fn verify_deposit_signature(deposit_data: &DepositData, spec: &ChainSpec) -> Result<()> {
+    let deposit_signature_message = deposit_pubkey_signature_message(&deposit_data)
        .ok_or_else(|| error(DepositInvalid::BadBlsBytes))?;

    verify!(
-        deposit_signature_set(state, &deposit_signature_message, spec).is_valid(),
+        deposit_signature_set(&deposit_signature_message, spec).is_valid(),
        DepositInvalid::BadSignature
    );

@@ -216,7 +216,7 @@ impl<T: EthSpec> BeaconState<T> {
            // Versioning
            genesis_time,
            slot: spec.genesis_slot,
-            fork: Fork::genesis(T::genesis_epoch()),
+            fork: spec.genesis_fork.clone(),

            // History
            latest_block_header: BeaconBlock::<T>::empty(spec).temporary_block_header(),
@@ -91,8 +91,15 @@ pub struct ChainSpec {
    domain_voluntary_exit: u32,
    domain_transfer: u32,

+    /*
+     * Eth1
+     */
+    pub eth1_follow_distance: u64,
+
    pub boot_nodes: Vec<String>,
    pub network_id: u8,
+
+    pub genesis_fork: Fork,
 }

 impl ChainSpec {
@@ -118,6 +125,22 @@ impl ChainSpec {
        u64::from_le_bytes(fork_and_domain)
    }

+    /// Get the domain for a deposit signature.
+    ///
+    /// Deposits are valid across forks, thus the deposit domain is computed
+    /// with the fork zeroed.
+    ///
+    /// Spec v0.8.1
+    pub fn get_deposit_domain(&self) -> u64 {
+        let mut bytes: Vec<u8> = int_to_bytes4(self.domain_deposit);
+        bytes.append(&mut vec![0; 4]);
+
+        let mut fork_and_domain = [0; 8];
+        fork_and_domain.copy_from_slice(&bytes);
+
+        u64::from_le_bytes(fork_and_domain)
+    }
+
    /// Returns a `ChainSpec` compatible with the Ethereum Foundation specification.
    ///
    /// Spec v0.8.1
@@ -186,6 +209,20 @@ impl ChainSpec {
            domain_voluntary_exit: 4,
            domain_transfer: 5,

+            /*
+             * Eth1
+             */
+            eth1_follow_distance: 1_024,
+
+            /*
+             * Fork
+             */
+            genesis_fork: Fork {
+                previous_version: [0; 4],
+                current_version: [0; 4],
+                epoch: Epoch::new(0),
+            },
+
            /*
             * Network specific
             */
@@ -210,6 +247,7 @@ impl ChainSpec {
            max_epochs_per_crosslink: 4,
            network_id: 2, // lighthouse testnet network id
            boot_nodes,
+            eth1_follow_distance: 16,
            ..ChainSpec::mainnet()
        }
    }
@@ -248,7 +286,7 @@ mod tests {
    }

    fn test_domain(domain_type: Domain, raw_domain: u32, spec: &ChainSpec) {
-        let fork = Fork::genesis(Epoch::new(0));
+        let fork = &spec.genesis_fork;
        let epoch = Epoch::new(0);

        let domain = spec.get_domain(epoch, domain_type, &fork);
@@ -7,6 +7,8 @@ use ssz_derive::{Decode, Encode};
 use test_random_derive::TestRandom;
 use tree_hash_derive::TreeHash;

+pub const DEPOSIT_TREE_DEPTH: usize = 32;
+
 /// A deposit to potentially become a beacon chain validator.
 ///
 /// Spec v0.8.0
@@ -36,15 +36,9 @@ impl DepositData {
    /// Generate the signature for a given DepositData details.
    ///
    /// Spec v0.8.1
-    pub fn create_signature(
-        &self,
-        secret_key: &SecretKey,
-        epoch: Epoch,
-        fork: &Fork,
-        spec: &ChainSpec,
-    ) -> SignatureBytes {
+    pub fn create_signature(&self, secret_key: &SecretKey, spec: &ChainSpec) -> SignatureBytes {
        let msg = self.signed_root();
-        let domain = spec.get_domain(epoch, Domain::Deposit, fork);
+        let domain = spec.get_deposit_domain();

        SignatureBytes::from(Signature::new(msg.as_slice(), domain, secret_key))
    }
@@ -10,7 +10,18 @@ use tree_hash_derive::TreeHash;
 ///
 /// Spec v0.8.1
 #[derive(
-    Debug, PartialEq, Clone, Default, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+    Debug,
+    PartialEq,
+    Clone,
+    Default,
+    Eq,
+    Hash,
+    Serialize,
+    Deserialize,
+    Encode,
+    Decode,
+    TreeHash,
+    TestRandom,
 )]
 pub struct Eth1Data {
    pub deposit_root: Hash256,
@@ -28,17 +28,6 @@ pub struct Fork {
 }

 impl Fork {
-    /// Initialize the `Fork` from the genesis parameters in the `spec`.
-    ///
-    /// Spec v0.8.1
-    pub fn genesis(genesis_epoch: Epoch) -> Self {
-        Self {
-            previous_version: [0; 4],
-            current_version: [0; 4],
-            epoch: genesis_epoch,
-        }
-    }
-
    /// Return the fork version of the given ``epoch``.
    ///
    /// Spec v0.8.1
@@ -56,24 +45,6 @@ mod tests {

    ssz_tests!(Fork);

-    fn test_genesis(epoch: Epoch) {
-        let fork = Fork::genesis(epoch);
-
-        assert_eq!(fork.epoch, epoch, "epoch incorrect");
-        assert_eq!(
-            fork.previous_version, fork.current_version,
-            "previous and current are not identical"
-        );
-    }
-
-    #[test]
-    fn genesis() {
-        test_genesis(Epoch::new(0));
-        test_genesis(Epoch::new(11));
-        test_genesis(Epoch::new(2_u64.pow(63)));
-        test_genesis(Epoch::max_value());
-    }
-
    #[test]
    fn get_fork_version() {
        let previous_version = [1; 4];
@@ -58,7 +58,7 @@ pub use crate::checkpoint::Checkpoint;
 pub use crate::compact_committee::CompactCommittee;
 pub use crate::crosslink::Crosslink;
 pub use crate::crosslink_committee::{CrosslinkCommittee, OwnedCrosslinkCommittee};
-pub use crate::deposit::Deposit;
+pub use crate::deposit::{Deposit, DEPOSIT_TREE_DEPTH};
 pub use crate::deposit_data::DepositData;
 pub use crate::eth1_data::Eth1Data;
 pub use crate::fork::Fork;
@@ -294,13 +294,7 @@ impl<T: EthSpec> TestingBeaconBlockBuilder<T> {
            let keypair = Keypair::random();

            let mut builder = TestingDepositBuilder::new(keypair.pk.clone(), amount);
-            builder.sign(
-                &test_task,
-                &keypair,
-                state.slot.epoch(T::slots_per_epoch()),
-                &state.fork,
-                spec,
-            );
+            builder.sign(&test_task, &keypair, spec);
            datas.push(builder.build().data);
        }

@@ -30,14 +30,7 @@ impl TestingDepositBuilder {
    /// - `pubkey` to the signing pubkey.
    /// - `withdrawal_credentials` to the signing pubkey.
    /// - `proof_of_possession`
-    pub fn sign(
-        &mut self,
-        test_task: &DepositTestTask,
-        keypair: &Keypair,
-        epoch: Epoch,
-        fork: &Fork,
-        spec: &ChainSpec,
-    ) {
+    pub fn sign(&mut self, test_task: &DepositTestTask, keypair: &Keypair, spec: &ChainSpec) {
        let new_key = Keypair::random();
        let mut pubkeybytes = PublicKeyBytes::from(keypair.pk.clone());
        let mut secret_key = keypair.sk.clone();
@@ -61,10 +54,7 @@ impl TestingDepositBuilder {
        // Building the data and signing it
        self.deposit.data.pubkey = pubkeybytes;
        self.deposit.data.withdrawal_credentials = withdrawal_credentials;
-        self.deposit.data.signature =
-            self.deposit
-                .data
-                .create_signature(&secret_key, epoch, fork, spec);
+        self.deposit.data.signature = self.deposit.data.create_signature(&secret_key, spec);
    }

    /// Builds the deposit, consuming the builder.
@@ -5,7 +5,6 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 edition = "2018"

 [dependencies]
-clap = "2.33.0"
 serde = "1.0.102"
 serde_derive = "1.0.102"
 toml = "0.5.4"
@@ -1,9 +1,7 @@
-use clap::ArgMatches;
 use serde_derive::{Deserialize, Serialize};
 use std::fs::File;
 use std::io::prelude::*;
 use std::path::PathBuf;
-use std::time::SystemTime;
 use types::ChainSpec;

 /// The core configuration of a Lighthouse beacon node.
@@ -46,33 +44,6 @@ impl Eth2Config {
    }
 }

-impl Eth2Config {
-    /// Apply the following arguments to `self`, replacing values if they are specified in `args`.
-    ///
-    /// Returns an error if arguments are obviously invalid. May succeed even if some values are
-    /// invalid.
-    pub fn apply_cli_args(&mut self, args: &ArgMatches) -> Result<(), &'static str> {
-        if args.is_present("recent-genesis") {
-            self.spec.min_genesis_time = recent_genesis_time()
-        }
-
-        Ok(())
-    }
-}
-
-/// Returns the system time, mod 30 minutes.
-///
-/// Used for easily creating testnets.
-fn recent_genesis_time() -> u64 {
-    let now = SystemTime::now()
-        .duration_since(SystemTime::UNIX_EPOCH)
-        .unwrap()
-        .as_secs();
-    let secs_after_last_period = now.checked_rem(30 * 60).unwrap_or(0);
-    // genesis is now the last 30 minute block.
-    now - secs_after_last_period
-}
-
 /// Write a configuration to file.
 pub fn write_to_file<T>(path: PathBuf, config: &T) -> Result<(), String>
 where
@@ -111,3 +82,15 @@ where
        Ok(None)
    }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use toml;
+
+    #[test]
+    fn serde_serialize() {
+        let _ =
+            toml::to_string(&Eth2Config::default()).expect("Should serde encode default config");
+    }
+}
@@ -0,0 +1,14 @@
+[package]
+name = "remote_beacon_node"
+version = "0.1.0"
+authors = ["Paul Hauner <paul@paulhauner.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+reqwest = "0.9"
+url = "1.2"
+serde = "1.0"
+futures = "0.1.25"
+types = { path = "../../../eth2/types" }
@@ -0,0 +1,141 @@
+//! Provides a `RemoteBeaconNode` which interacts with a HTTP API on another Lighthouse (or
+//! compatible) instance.
+//!
+//! Presently, this is only used for testing but it _could_ become a user-facing library.
+
+use futures::{Future, IntoFuture};
+use reqwest::r#async::{Client, RequestBuilder};
+use serde::Deserialize;
+use std::marker::PhantomData;
+use std::net::SocketAddr;
+use types::{BeaconBlock, BeaconState, EthSpec};
+use types::{Hash256, Slot};
+use url::Url;
+
+/// Connects to a remote Lighthouse (or compatible) node via HTTP.
+pub struct RemoteBeaconNode<E: EthSpec> {
+    pub http: HttpClient<E>,
+}
+
+impl<E: EthSpec> RemoteBeaconNode<E> {
+    pub fn new(http_endpoint: SocketAddr) -> Result<Self, String> {
+        Ok(Self {
+            http: HttpClient::new(format!("http://{}", http_endpoint.to_string()))
+                .map_err(|e| format!("Unable to create http client: {:?}", e))?,
+        })
+    }
+}
+
+#[derive(Debug)]
+pub enum Error {
+    UrlParseError(url::ParseError),
+    ReqwestError(reqwest::Error),
+}
+
+#[derive(Clone)]
+pub struct HttpClient<E> {
+    client: Client,
+    url: Url,
+    _phantom: PhantomData<E>,
+}
+
+impl<E: EthSpec> HttpClient<E> {
+    /// Creates a new instance (without connecting to the node).
+    pub fn new(server_url: String) -> Result<Self, Error> {
+        Ok(Self {
+            client: Client::new(),
+            url: Url::parse(&server_url)?,
+            _phantom: PhantomData,
+        })
+    }
+
+    pub fn beacon(&self) -> Beacon<E> {
+        Beacon(self.clone())
+    }
+
+    fn url(&self, path: &str) -> Result<Url, Error> {
+        self.url.join(path).map_err(|e| e.into())
+    }
+
+    pub fn get(&self, path: &str) -> Result<RequestBuilder, Error> {
+        self.url(path)
+            .map(|url| Client::new().get(&url.to_string()))
+    }
+}
+
+/// Provides the functions on the `/beacon` endpoint of the node.
+#[derive(Clone)]
+pub struct Beacon<E>(HttpClient<E>);
+
+impl<E: EthSpec> Beacon<E> {
+    fn url(&self, path: &str) -> Result<Url, Error> {
+        self.0
+            .url("beacon/")
+            .and_then(move |url| url.join(path).map_err(Error::from))
+            .map_err(Into::into)
+    }
+
+    /// Returns the block and block root at the given slot.
+    pub fn block_at_slot(
+        &self,
+        slot: Slot,
+    ) -> impl Future<Item = (BeaconBlock<E>, Hash256), Error = Error> {
+        let client = self.0.clone();
+        self.url("block")
+            .into_future()
+            .and_then(move |mut url| {
+                url.query_pairs_mut()
+                    .append_pair("slot", &format!("{}", slot.as_u64()));
+                client.get(&url.to_string())
+            })
+            .and_then(|builder| builder.send().map_err(Error::from))
+            .and_then(|response| response.error_for_status().map_err(Error::from))
+            .and_then(|mut success| success.json::<BlockResponse<E>>().map_err(Error::from))
+            .map(|response| (response.beacon_block, response.root))
+    }
+
+    /// Returns the state and state root at the given slot.
+    pub fn state_at_slot(
+        &self,
+        slot: Slot,
+    ) -> impl Future<Item = (BeaconState<E>, Hash256), Error = Error> {
+        let client = self.0.clone();
+        self.url("state")
+            .into_future()
+            .and_then(move |mut url| {
+                url.query_pairs_mut()
+                    .append_pair("slot", &format!("{}", slot.as_u64()));
+                client.get(&url.to_string())
+            })
+            .and_then(|builder| builder.send().map_err(Error::from))
+            .and_then(|response| response.error_for_status().map_err(Error::from))
+            .and_then(|mut success| success.json::<StateResponse<E>>().map_err(Error::from))
+            .map(|response| (response.beacon_state, response.root))
+    }
+}
+
+#[derive(Deserialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct BlockResponse<T: EthSpec> {
+    pub beacon_block: BeaconBlock<T>,
+    pub root: Hash256,
+}
+
+#[derive(Deserialize)]
+#[serde(bound = "T: EthSpec")]
+pub struct StateResponse<T: EthSpec> {
+    pub beacon_state: BeaconState<T>,
+    pub root: Hash256,
+}
+
+impl From<reqwest::Error> for Error {
+    fn from(e: reqwest::Error) -> Error {
+        Error::ReqwestError(e)
+    }
+}
+
+impl From<url::ParseError> for Error {
+    fn from(e: url::ParseError) -> Error {
+        Error::UrlParseError(e)
+    }
+}