Allow validator client to start before genesis

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -178,7 +178,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             genesis_state.genesis_time,
             Duration::from_millis(spec.milliseconds_per_slot),
         )
-        .ok_or_else(|| Error::SlotClockDidNotStart)?;
+        .map_err(|_| Error::SlotClockDidNotStart)?;
 
         info!(log, "Beacon chain initialized from genesis";
               "validator_count" => genesis_state.validators.len(),
@@ -220,7 +220,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             state.genesis_time,
             Duration::from_millis(spec.milliseconds_per_slot),
         )
-        .ok_or_else(|| Error::SlotClockDidNotStart)?;
+        .map_err(|_| Error::SlotClockDidNotStart)?;
 
         let last_finalized_root = p.canonical_head.beacon_state.finalized_checkpoint.root;
         let last_finalized_block = &p.canonical_head.beacon_block;

beacon_node/client/src/lib.rs

@@ -16,7 +16,7 @@ use slog::{crit, error, info, o};
 use slot_clock::SlotClock;
 use std::marker::PhantomData;
 use std::sync::Arc;
-use std::time::{Duration, Instant};
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 use tokio::runtime::TaskExecutor;
 use tokio::timer::Interval;
 use types::EthSpec;
@@ -177,8 +177,18 @@ where
                 .map_err(error::Error::from)?,
         );
 
-        if beacon_chain.slot().is_err() {
-            panic!("Cannot start client before genesis!")
+        let since_epoch = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map_err(|e| format!("Unable to read system time: {}", e))?;
+        let since_genesis = Duration::from_secs(beacon_chain.head().beacon_state.genesis_time);
+
+        if since_genesis > since_epoch {
+            info!(
+                log,
+                "Starting node prior to genesis";
+                "now" => since_epoch.as_secs(),
+                "genesis_seconds" => since_genesis.as_secs(),
+            );
         }
 
         let network_config = &client_config.network;

eth2/utils/slot_clock/src/lib.rs

@@ -5,7 +5,7 @@ mod metrics;
 mod system_time_slot_clock;
 mod testing_slot_clock;
 
-use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+use std::time::{Duration, Instant, SystemTime, SystemTimeError, UNIX_EPOCH};
 
 pub use crate::system_time_slot_clock::SystemTimeSlotClock;
 pub use crate::testing_slot_clock::TestingSlotClock;
@@ -17,18 +17,21 @@ pub trait SlotClock: Send + Sync + Sized {
         genesis_slot: Slot,
         genesis_seconds: u64,
         slot_duration: Duration,
-    ) -> Option<Self> {
-        let duration_between_now_and_unix_epoch =
-            SystemTime::now().duration_since(UNIX_EPOCH).ok()?;
+    ) -> Result<Self, SystemTimeError> {
+        let duration_between_now_and_unix_epoch = SystemTime::now().duration_since(UNIX_EPOCH)?;
         let duration_between_unix_epoch_and_genesis = Duration::from_secs(genesis_seconds);
 
-        if duration_between_now_and_unix_epoch < duration_between_unix_epoch_and_genesis {
-            None
+        let genesis_instant = if duration_between_now_and_unix_epoch
+            < duration_between_unix_epoch_and_genesis
+        {
+            Instant::now()
+                + (duration_between_unix_epoch_and_genesis - duration_between_now_and_unix_epoch)
         } else {
-            let genesis_instant = Instant::now()
-                - (duration_between_now_and_unix_epoch - duration_between_unix_epoch_and_genesis);
-            Some(Self::new(genesis_slot, genesis_instant, slot_duration))
-        }
+            Instant::now()
+                - (duration_between_now_and_unix_epoch - duration_between_unix_epoch_and_genesis)
+        };
+
+        Ok(Self::new(genesis_slot, genesis_instant, slot_duration))
     }
 
     fn new(genesis_slot: Slot, genesis: Instant, slot_duration: Duration) -> Self;

eth2/utils/slot_clock/src/system_time_slot_clock.rs

@@ -42,7 +42,7 @@ impl SlotClock for SystemTimeSlotClock {
     fn duration_to_next_slot(&self) -> Option<Duration> {
         let now = Instant::now();
         if now < self.genesis {
-            None
+            Some(self.genesis - now)
         } else {
             let duration_since_genesis = now - self.genesis;
             let millis_since_genesis = duration_since_genesis.as_millis();

validator_client/src/service.rs

@@ -27,7 +27,7 @@ use slot_clock::{SlotClock, SystemTimeSlotClock};
 use std::marker::PhantomData;
 use std::sync::Arc;
 use std::sync::RwLock;
-use std::time::{Duration, Instant, SystemTime};
+use std::time::{Duration, Instant};
 use tokio::prelude::*;
 use tokio::runtime::Builder;
 use tokio::timer::Interval;
@@ -100,19 +100,6 @@ impl<B: BeaconNodeDuties + 'static, S: Signer + 'static, E: EthSpec> Service<B,
                     continue;
                 }
                 Ok(info) => {
-                    // verify the node's genesis time
-                    if SystemTime::now()
-                        .duration_since(SystemTime::UNIX_EPOCH)
-                        .unwrap()
-                        .as_secs()
-                        < info.genesis_time
-                    {
-                        error!(
-                            log,
-                            "Beacon Node's genesis time is in the future. No work to do.\n Exiting"
-                        );
-                        return Err("Genesis time in the future".into());
-                    }
                     // verify the node's network id
                     if eth2_config.spec.network_id != info.network_id as u8 {
                         error!(
@@ -177,13 +164,11 @@ impl<B: BeaconNodeDuties + 'static, S: Signer + 'static, E: EthSpec> Service<B,
             genesis_time,
             Duration::from_millis(eth2_config.spec.milliseconds_per_slot),
         )
-        .ok_or_else::<error_chain::Error, _>(|| {
-            "Unable to start slot clock. Genesis may not have occurred yet. Exiting.".into()
+        .map_err::<error_chain::Error, _>(|e| {
+            format!("Unable to start slot clock: {}.", e).into()
         })?;
 
-        let current_slot = slot_clock.now().ok_or_else::<error_chain::Error, _>(|| {
-            "Genesis has not yet occurred. Exiting.".into()
-        })?;
+        let current_slot = slot_clock.now().unwrap_or_else(|| Slot::new(0));
 
         /* Generate the duties manager */
 
@@ -237,7 +222,7 @@ impl<B: BeaconNodeDuties + 'static, S: Signer + 'static, E: EthSpec> Service<B,
         let mut service = Service::<ValidatorServiceClient, Keypair, E>::initialize_service(
             client_config,
             eth2_config,
-            log,
+            log.clone(),
         )?;
 
         // we have connected to a node and established its parameters. Spin up the core service
@@ -253,7 +238,7 @@ impl<B: BeaconNodeDuties + 'static, S: Signer + 'static, E: EthSpec> Service<B,
             .slot_clock
             .duration_to_next_slot()
             .ok_or_else::<error_chain::Error, _>(|| {
-                "Genesis is not in the past. Exiting.".into()
+                "Unable to determine duration to next slot. Exiting.".into()
             })?;
 
         // set up the validator work interval - start at next slot and proceed every slot
@@ -264,6 +249,19 @@ impl<B: BeaconNodeDuties + 'static, S: Signer + 'static, E: EthSpec> Service<B,
             Interval::new(Instant::now() + duration_to_next_slot, slot_duration)
         };
 
+        if service.slot_clock.now().is_none() {
+            warn!(
+                log,
+                "Starting node prior to genesis";
+            );
+        }
+
+        info!(
+            log,
+            "Waiting for next slot";
+            "seconds_to_wait" => duration_to_next_slot.as_secs()
+        );
+
         /* kick off the core service */
         runtime.block_on(
             interval