Testnet stability (#451)

* Change reduced tree for adding weightless node

* Add more comments for reduced tree fork choice

* Small refactor on reduced tree for readability

* Move test_harness forking logic into itself

* Add new `AncestorIter` trait to store

* Add unfinished tests to fork choice

* Make `beacon_state.genesis_block_root` public

* Add failing lmd_ghost fork choice tests

* Extend fork_choice tests, create failing test

* Implement Debug for generic ReducedTree

* Add lazy_static to fork choice tests

* Add verify_integrity fn to reduced tree

* Fix bugs in reduced tree

* Ensure all reduced tree tests verify integrity

* Slightly alter reduce tree test params

* Add (failing) reduced tree test

* Fix bug in fork choice

Iter ancestors was not working well with skip slots

* Put maximum depth for common ancestor search

Ensures that we don't search back past the finalized root.

* Add basic finalization tests for reduced tree

* Change fork choice to use beacon_block_root

Previously it was using target_root, which was wrong

* Change reduced tree for adding weightless node

* Add more comments for reduced tree fork choice

* Small refactor on reduced tree for readability

* Move test_harness forking logic into itself

* Add new `AncestorIter` trait to store

* Add unfinished tests to fork choice

* Make `beacon_state.genesis_block_root` public

* Add failing lmd_ghost fork choice tests

* Extend fork_choice tests, create failing test

* Implement Debug for generic ReducedTree

* Add lazy_static to fork choice tests

* Add verify_integrity fn to reduced tree

* Fix bugs in reduced tree

* Ensure all reduced tree tests verify integrity

* Slightly alter reduce tree test params

* Add (failing) reduced tree test

* Fix bug in fork choice

Iter ancestors was not working well with skip slots

* Put maximum depth for common ancestor search

Ensures that we don't search back past the finalized root.

* Add basic finalization tests for reduced tree

* Add network dir CLI flag

* Simplify "NewSlot" log message

* Rename network-dir CLI flag

* Change fork choice to use beacon_block_root

Previously it was using target_root, which was wrong

* Update db dir size for metrics

* Change slog to use `FullFormat` logging

* Update some comments and log formatting

* Add prom gauge for best block root

* Only add known target blocks to fork choice

* Add finalized and justified root prom metrics

* Add CLI flag for setting log level

* Add logger to beacon chain

* Add debug-level CLI flag to validator

* Allow block processing if fork choice fails

* Create warn log when there's low libp2p peer count

* Minor change to logging

* Make ancestor iter return option

* Disable fork choice test when !debug_assertions

* Fix type, removed code fragment

* Tidy some borrow-checker evading

* Lower reduced tree random test iterations

beacon_node/beacon_chain/Cargo.toml

@@ -12,6 +12,8 @@ log = "0.4"
 operation_pool = { path = "../../eth2/operation_pool" }
 serde = "1.0"
 serde_derive = "1.0"
+slog = { version = "^2.2.3" , features = ["max_level_trace"] }
+sloggers = { version = "^0.3" }
 slot_clock = { path = "../../eth2/utils/slot_clock" }
 eth2_ssz = { path = "../../eth2/utils/ssz" }
 eth2_ssz_derive = { path = "../../eth2/utils/ssz_derive" }

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -8,6 +8,7 @@ use log::trace;
 use operation_pool::DepositInsertStatus;
 use operation_pool::{OperationPool, PersistedOperationPool};
 use parking_lot::{RwLock, RwLockReadGuard};
+use slog::{error, info, warn, Logger};
 use slot_clock::SlotClock;
 use state_processing::per_block_processing::errors::{
     AttestationValidationError, AttesterSlashingValidationError, DepositValidationError,
@@ -83,6 +84,8 @@ pub struct BeaconChain<T: BeaconChainTypes> {
     pub fork_choice: ForkChoice<T>,
     /// Stores metrics about this `BeaconChain`.
     pub metrics: Metrics,
+    /// Logging to CLI, etc.
+    log: Logger,
 }
 
 impl<T: BeaconChainTypes> BeaconChain<T> {
@@ -93,6 +96,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         mut genesis_state: BeaconState<T::EthSpec>,
         genesis_block: BeaconBlock,
         spec: ChainSpec,
+        log: Logger,
     ) -> Result<Self, Error> {
         genesis_state.build_all_caches(&spec)?;
 
@@ -123,6 +127,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             fork_choice: ForkChoice::new(store.clone(), &genesis_block, genesis_block_root),
             metrics: Metrics::new()?,
             store,
+            log,
         })
     }
 
@@ -130,6 +135,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     pub fn from_store(
         store: Arc<T::Store>,
         spec: ChainSpec,
+        log: Logger,
     ) -> Result<Option<BeaconChain<T>>, Error> {
         let key = Hash256::from_slice(&BEACON_CHAIN_DB_KEY.as_bytes());
         let p: PersistedBeaconChain<T> = match store.get(&key) {
@@ -159,6 +165,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             genesis_block_root: p.genesis_block_root,
             metrics: Metrics::new()?,
             store,
+            log,
         }))
     }
 
@@ -646,13 +653,27 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         self.store.put(&state_root, &state)?;
 
         // Register the new block with the fork choice service.
-        self.fork_choice.process_block(&state, &block, block_root)?;
+        if let Err(e) = self.fork_choice.process_block(&state, &block, block_root) {
+            error!(
+                self.log,
+                "fork choice failed to process_block";
+                "error" => format!("{:?}", e),
+                "block_root" =>  format!("{}", block_root),
+                "block_slot" => format!("{}", block.slot)
+            )
+        }
 
         // Execute the fork choice algorithm, enthroning a new head if discovered.
         //
         // Note: in the future we may choose to run fork-choice less often, potentially based upon
         // some heuristic around number of attestations seen for the block.
-        self.fork_choice()?;
+        if let Err(e) = self.fork_choice() {
+            error!(
+                self.log,
+                "fork choice failed to find head";
+                "error" => format!("{:?}", e)
+            )
+        };
 
         self.metrics.block_processing_successes.inc();
         self.metrics
@@ -780,9 +801,27 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 .get(&beacon_state_root)?
                 .ok_or_else(|| Error::MissingBeaconState(beacon_state_root))?;
 
+            let previous_slot = self.head().beacon_block.slot;
+            let new_slot = beacon_block.slot;
+
             // If we switched to a new chain (instead of building atop the present chain).
             if self.head().beacon_block_root != beacon_block.previous_block_root {
                 self.metrics.fork_choice_reorg_count.inc();
+                warn!(
+                    self.log,
+                    "Beacon chain re-org";
+                    "previous_slot" => previous_slot,
+                    "new_slot" => new_slot
+                );
+            } else {
+                info!(
+                    self.log,
+                    "new head block";
+                    "justified_root" => format!("{}", beacon_state.current_justified_root),
+                    "finalized_root" => format!("{}", beacon_state.finalized_root),
+                    "root" => format!("{}", beacon_block_root),
+                    "slot" => new_slot,
+                );
             };
 
             let old_finalized_epoch = self.head().beacon_state.finalized_epoch;

beacon_node/beacon_chain/src/fork_choice.rs

@@ -18,6 +18,7 @@ pub enum Error {
 
 pub struct ForkChoice<T: BeaconChainTypes> {
     backend: T::LmdGhost,
+    store: Arc<T::Store>,
     /// Used for resolving the `0x00..00` alias back to genesis.
     ///
     /// Does not necessarily need to be the _actual_ genesis, it suffices to be the finalized root
@@ -36,6 +37,7 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         genesis_block_root: Hash256,
     ) -> Self {
         Self {
+            store: store.clone(),
             backend: T::LmdGhost::new(store, genesis_block, genesis_block_root),
             genesis_block_root,
         }
@@ -125,13 +127,6 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         state: &BeaconState<T::EthSpec>,
         attestation: &Attestation,
     ) -> Result<()> {
-        let validator_indices = get_attesting_indices_unsorted(
-            state,
-            &attestation.data,
-            &attestation.aggregation_bitfield,
-        )?;
-        let block_slot = state.get_attestation_slot(&attestation.data)?;
-
         let block_hash = attestation.data.beacon_block_root;
 
         // Ignore any attestations to the zero hash.
@@ -147,7 +142,22 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         // (1) becomes weird once we hit finality and fork choice drops the genesis block. (2) is
         // fine because votes to the genesis block are not useful; all validators implicitly attest
         // to genesis just by being present in the chain.
-        if block_hash != Hash256::zero() {
+        //
+        // Additionally, don't add any block hash to fork choice unless we have imported the block.
+        if block_hash != Hash256::zero()
+            && self
+                .store
+                .exists::<BeaconBlock>(&block_hash)
+                .unwrap_or(false)
+        {
+            let validator_indices = get_attesting_indices_unsorted(
+                state,
+                &attestation.data,
+                &attestation.aggregation_bitfield,
+            )?;
+
+            let block_slot = state.get_attestation_slot(&attestation.data)?;
+
             for validator_index in validator_indices {
                 self.backend
                     .process_attestation(validator_index, block_hash, block_slot)?;

beacon_node/beacon_chain/src/test_utils.rs

@@ -1,5 +1,6 @@
 use crate::{BeaconChain, BeaconChainTypes, BlockProcessingOutcome};
 use lmd_ghost::LmdGhost;
+use sloggers::{null::NullLoggerBuilder, Build};
 use slot_clock::SlotClock;
 use slot_clock::TestingSlotClock;
 use state_processing::per_slot_processing;
@@ -94,6 +95,9 @@ where
         let mut genesis_block = BeaconBlock::empty(&spec);
         genesis_block.state_root = Hash256::from_slice(&genesis_state.tree_hash_root());
 
+        let builder = NullLoggerBuilder;
+        let log = builder.build().expect("logger should build");
+
         // Slot clock
         let slot_clock = TestingSlotClock::new(
             spec.genesis_slot,
@@ -107,6 +111,7 @@ where
             genesis_state,
             genesis_block,
             spec.clone(),
+            log,
         )
         .expect("Terminate if beacon chain generation fails");
 

beacon_node/client/src/beacon_chain_types.rs

@@ -49,7 +49,9 @@ where
     T: BeaconChainTypes<Store = U, EthSpec = V>,
     T::LmdGhost: LmdGhost<U, V>,
 {
-    if let Ok(Some(beacon_chain)) = BeaconChain::from_store(store.clone(), spec.clone()) {
+    if let Ok(Some(beacon_chain)) =
+        BeaconChain::from_store(store.clone(), spec.clone(), log.clone())
+    {
         info!(
             log,
             "Loaded BeaconChain from store";
@@ -78,7 +80,7 @@ where
 
         // Genesis chain
         //TODO: Handle error correctly
-        BeaconChain::from_genesis(store, slot_clock, genesis_state, genesis_block, spec)
+        BeaconChain::from_genesis(store, slot_clock, genesis_state, genesis_block, spec, log)
             .expect("Terminate if beacon chain generation fails")
     }
 }

beacon_node/client/src/lib.rs

@@ -190,29 +190,38 @@ impl<T: BeaconChainTypes> Drop for Client<T> {
 }
 
 fn do_state_catchup<T: BeaconChainTypes>(chain: &Arc<BeaconChain<T>>, log: &slog::Logger) {
-    if let Some(genesis_height) = chain.slots_since_genesis() {
+    // Only attempt to `catchup_state` if we can read the slot clock.
-        let result = chain.catchup_state();
+    if let Some(current_slot) = chain.read_slot_clock() {
+        let state_catchup_result = chain.catchup_state();
+
+        let best_slot = chain.head().beacon_block.slot;
+        let latest_block_root = chain.head().beacon_block_root;
 
         let common = o!(
-            "best_slot" => chain.head().beacon_block.slot,
+            "skip_slots" => current_slot.saturating_sub(best_slot),
-            "latest_block_root" => format!("{}", chain.head().beacon_block_root),
+            "best_block_root" => format!("{}", latest_block_root),
-            "wall_clock_slot" => chain.read_slot_clock().unwrap(),
+            "best_block_slot" => best_slot,
-            "state_slot" => chain.head().beacon_state.slot,
+            "slot" => current_slot,
-            "slots_since_genesis" => genesis_height,
         );
 
-        match result {
+        if let Err(e) = state_catchup_result {
-            Ok(_) => info!(
+            error!(
                 log,
-                "NewSlot";
+                "State catchup failed";
-                common
-            ),
-            Err(e) => error!(
-                log,
-                "StateCatchupFailed";
                 "error" => format!("{:?}", e),
                 common
-            ),
+            )
-        };
+        } else {
+            info!(
+                log,
+                "Slot start";
+                common
+            )
         }
+    } else {
+        error!(
+            log,
+            "Beacon chain running whilst slot clock is unavailable."
+        );
+    };
 }

beacon_node/client/src/notifier.rs

@@ -2,7 +2,7 @@ use crate::Client;
 use beacon_chain::BeaconChainTypes;
 use exit_future::Exit;
 use futures::{Future, Stream};
-use slog::{debug, o};
+use slog::{debug, o, warn};
 use std::time::{Duration, Instant};
 use tokio::runtime::TaskExecutor;
 use tokio::timer::Interval;
@@ -10,6 +10,9 @@ use tokio::timer::Interval;
 /// The interval between heartbeat events.
 pub const HEARTBEAT_INTERVAL_SECONDS: u64 = 15;
 
+/// Create a warning log whenever the peer count is at or below this value.
+pub const WARN_PEER_COUNT: usize = 1;
+
 /// Spawns a thread that can be used to run code periodically, on `HEARTBEAT_INTERVAL_SECONDS`
 /// durations.
 ///
@@ -30,9 +33,16 @@ pub fn run<T: BeaconChainTypes + Send + Sync + 'static>(
     let libp2p = client.network.libp2p_service();
 
     let heartbeat = move |_| {
-        // Notify the number of connected nodes
+        // Number of libp2p (not discv5) peers connected.
-        // Panic if libp2p is poisoned
+        //
-        debug!(log, ""; "Connected Peers" => libp2p.lock().swarm.connected_peers());
+        // Panics if libp2p is poisoned.
+        let connected_peer_count = libp2p.lock().swarm.connected_peers();
+
+        debug!(log, "libp2p"; "peer_count" => connected_peer_count);
+
+        if connected_peer_count <= WARN_PEER_COUNT {
+            warn!(log, "Low libp2p peer count"; "peer_count" => connected_peer_count);
+        }
 
         Ok(())
     };

beacon_node/eth2-libp2p/src/config.rs

@@ -79,10 +79,16 @@ impl Config {
     }
 
     pub fn apply_cli_args(&mut self, args: &ArgMatches) -> Result<(), String> {
+        // If a `datadir` has been specified, set the network dir to be inside it.
         if let Some(dir) = args.value_of("datadir") {
             self.network_dir = PathBuf::from(dir).join("network");
         };
 
+        // If a network dir has been specified, override the `datadir` definition.
+        if let Some(dir) = args.value_of("network-dir") {
+            self.network_dir = PathBuf::from(dir);
+        };
+
         if let Some(listen_address_str) = args.value_of("listen-address") {
             let listen_address = listen_address_str
                 .parse()

beacon_node/http_server/src/metrics/local_metrics.rs

@@ -1,7 +1,7 @@
 use beacon_chain::{BeaconChain, BeaconChainTypes};
 use prometheus::{IntGauge, Opts, Registry};
 use slot_clock::SlotClock;
-use std::fs::File;
+use std::fs;
 use std::path::PathBuf;
 use types::{EthSpec, Slot};
 
@@ -13,6 +13,9 @@ pub struct LocalMetrics {
     present_slot: IntGauge,
     present_epoch: IntGauge,
     best_slot: IntGauge,
+    best_beacon_block_root: IntGauge,
+    justified_beacon_block_root: IntGauge,
+    finalized_beacon_block_root: IntGauge,
     validator_count: IntGauge,
     justified_epoch: IntGauge,
     finalized_epoch: IntGauge,
@@ -36,6 +39,24 @@ impl LocalMetrics {
                 let opts = Opts::new("best_slot", "slot_of_block_at_chain_head");
                 IntGauge::with_opts(opts)?
             },
+            best_beacon_block_root: {
+                let opts = Opts::new("best_beacon_block_root", "root_of_block_at_chain_head");
+                IntGauge::with_opts(opts)?
+            },
+            justified_beacon_block_root: {
+                let opts = Opts::new(
+                    "justified_beacon_block_root",
+                    "root_of_block_at_justified_head",
+                );
+                IntGauge::with_opts(opts)?
+            },
+            finalized_beacon_block_root: {
+                let opts = Opts::new(
+                    "finalized_beacon_block_root",
+                    "root_of_block_at_finalized_head",
+                );
+                IntGauge::with_opts(opts)?
+            },
             validator_count: {
                 let opts = Opts::new("validator_count", "number_of_validators");
                 IntGauge::with_opts(opts)?
@@ -64,6 +85,9 @@ impl LocalMetrics {
         registry.register(Box::new(self.present_slot.clone()))?;
         registry.register(Box::new(self.present_epoch.clone()))?;
         registry.register(Box::new(self.best_slot.clone()))?;
+        registry.register(Box::new(self.best_beacon_block_root.clone()))?;
+        registry.register(Box::new(self.justified_beacon_block_root.clone()))?;
+        registry.register(Box::new(self.finalized_beacon_block_root.clone()))?;
         registry.register(Box::new(self.validator_count.clone()))?;
         registry.register(Box::new(self.finalized_epoch.clone()))?;
         registry.register(Box::new(self.justified_epoch.clone()))?;
@@ -87,6 +111,22 @@ impl LocalMetrics {
             .set(present_slot.epoch(T::EthSpec::slots_per_epoch()).as_u64() as i64);
 
         self.best_slot.set(state.slot.as_u64() as i64);
+        self.best_beacon_block_root
+            .set(beacon_chain.head().beacon_block_root.to_low_u64_le() as i64);
+        self.justified_beacon_block_root.set(
+            beacon_chain
+                .head()
+                .beacon_state
+                .current_justified_root
+                .to_low_u64_le() as i64,
+        );
+        self.finalized_beacon_block_root.set(
+            beacon_chain
+                .head()
+                .beacon_state
+                .finalized_root
+                .to_low_u64_le() as i64,
+        );
         self.validator_count
             .set(state.validator_registry.len() as i64);
         self.justified_epoch
@@ -97,10 +137,17 @@ impl LocalMetrics {
             self.validator_balances_sum
                 .set(state.balances.iter().sum::<u64>() as i64);
         }
-        let db_size = File::open(db_path)
+        let db_size = if let Ok(iter) = fs::read_dir(db_path) {
-            .and_then(|f| f.metadata())
+            iter.filter_map(Result::ok)
-            .and_then(|m| Ok(m.len()))
+                .map(size_of_dir_entry)
-            .unwrap_or(0);
+                .fold(0_u64, |sum, val| sum + val)
+        } else {
+            0
+        };
         self.database_size.set(db_size as i64);
     }
 }
+
+fn size_of_dir_entry(dir: fs::DirEntry) -> u64 {
+    dir.metadata().map(|m| m.len()).unwrap_or(0)
+}

beacon_node/network/src/sync/simple_sync.rs

@@ -296,7 +296,7 @@ impl<T: BeaconChainTypes> SimpleSync<T> {
             .collect();
 
         if roots.len() as u64 != req.count {
-            warn!(
+            debug!(
                 self.log,
                 "BlockRootsRequest";
                 "peer" => format!("{:?}", peer_id),

beacon_node/src/main.rs

@@ -36,6 +36,13 @@ fn main() {
                 .help("File path where output will be written.")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("network-dir")
+                .long("network-dir")
+                .value_name("NETWORK-DIR")
+                .help("Data directory for network keys.")
+                .takes_value(true)
+        )
         // network related arguments
         .arg(
             Arg::with_name("listen-address")
@@ -145,6 +152,16 @@ fn main() {
                 .short("r")
                 .help("When present, genesis will be within 30 minutes prior. Only for testing"),
         )
+        .arg(
+            Arg::with_name("debug-level")
+                .long("debug-level")
+                .value_name("LEVEL")
+                .short("s")
+                .help("The title of the spec constants for chain config.")
+                .takes_value(true)
+                .possible_values(&["info", "debug", "trace", "warn", "error", "crit"])
+                .default_value("info"),
+        )
         .arg(
             Arg::with_name("verbosity")
                 .short("v")
@@ -156,9 +173,19 @@ fn main() {
 
     // build the initial logger
     let decorator = slog_term::TermDecorator::new().build();
-    let drain = slog_term::CompactFormat::new(decorator).build().fuse();
+    let drain = slog_term::FullFormat::new(decorator).build().fuse();
     let drain = slog_async::Async::new(drain).build();
 
+    let drain = match matches.value_of("debug-level") {
+        Some("info") => drain.filter_level(Level::Info),
+        Some("debug") => drain.filter_level(Level::Debug),
+        Some("trace") => drain.filter_level(Level::Trace),
+        Some("warn") => drain.filter_level(Level::Warning),
+        Some("error") => drain.filter_level(Level::Error),
+        Some("crit") => drain.filter_level(Level::Critical),
+        _ => unreachable!("guarded by clap"),
+    };
+
     let drain = match matches.occurrences_of("verbosity") {
         0 => drain.filter_level(Level::Info),
         1 => drain.filter_level(Level::Debug),
@@ -263,6 +290,7 @@ fn main() {
         }
     };
 
+    // Start the node using a `tokio` executor.
     match run::run_beacon_node(client_config, eth2_config, &log) {
         Ok(_) => {}
         Err(e) => crit!(log, "Beacon node failed to start"; "reason" => format!("{:}", e)),

beacon_node/src/run.rs

@@ -15,6 +15,12 @@ use tokio::runtime::TaskExecutor;
 use tokio_timer::clock::Clock;
 use types::{MainnetEthSpec, MinimalEthSpec};
 
+/// Reads the configuration and initializes a `BeaconChain` with the required types and parameters.
+///
+/// Spawns an executor which performs syncing, networking, block production, etc.
+///
+/// Blocks the current thread, returning after the `BeaconChain` has exited or a `Ctrl+C`
+/// signal.
 pub fn run_beacon_node(
     client_config: ClientConfig,
     eth2_config: Eth2Config,
@@ -38,7 +44,7 @@ pub fn run_beacon_node(
 
     warn!(
         log,
-        "This software is EXPERIMENTAL and provides no guarantees or warranties."
+        "Ethereum 2.0 is pre-release. This software is experimental."
     );
 
     info!(
@@ -46,6 +52,7 @@ pub fn run_beacon_node(
         "Starting beacon node";
         "p2p_listen_address" => format!("{:?}", &other_client_config.network.listen_address),
         "data_dir" => format!("{:?}", other_client_config.data_dir()),
+        "network_dir" => format!("{:?}", other_client_config.network.network_dir),
         "spec_constants" => &spec_constants,
         "db_type" => &other_client_config.db_type,
     );
@@ -92,7 +99,8 @@ pub fn run_beacon_node(
     result
 }
 
-pub fn run<T>(
+/// Performs the type-generic parts of launching a `BeaconChain`.
+fn run<T>(
     db_path: &Path,
     client_config: ClientConfig,
     eth2_config: Eth2Config,

validator_client/src/main.rs

@@ -11,7 +11,7 @@ use crate::service::Service as ValidatorService;
 use clap::{App, Arg};
 use eth2_config::{read_from_file, write_to_file, Eth2Config};
 use protos::services_grpc::ValidatorServiceClient;
-use slog::{crit, error, info, o, Drain};
+use slog::{crit, error, info, o, Drain, Level};
 use std::fs;
 use std::path::PathBuf;
 use types::{Keypair, MainnetEthSpec, MinimalEthSpec};
@@ -26,7 +26,6 @@ fn main() {
     let decorator = slog_term::TermDecorator::new().build();
     let drain = slog_term::CompactFormat::new(decorator).build().fuse();
     let drain = slog_async::Async::new(drain).build().fuse();
-    let mut log = slog::Logger::root(drain, o!());
 
     // CLI
     let matches = App::new("Lighthouse Validator Client")
@@ -73,8 +72,29 @@ fn main() {
                 .possible_values(&["mainnet", "minimal"])
                 .default_value("minimal"),
         )
+        .arg(
+            Arg::with_name("debug-level")
+                .long("debug-level")
+                .value_name("LEVEL")
+                .short("s")
+                .help("The title of the spec constants for chain config.")
+                .takes_value(true)
+                .possible_values(&["info", "debug", "trace", "warn", "error", "crit"])
+                .default_value("info"),
+        )
         .get_matches();
 
+    let drain = match matches.value_of("debug-level") {
+        Some("info") => drain.filter_level(Level::Info),
+        Some("debug") => drain.filter_level(Level::Debug),
+        Some("trace") => drain.filter_level(Level::Trace),
+        Some("warn") => drain.filter_level(Level::Warning),
+        Some("error") => drain.filter_level(Level::Error),
+        Some("crit") => drain.filter_level(Level::Critical),
+        _ => unreachable!("guarded by clap"),
+    };
+    let mut log = slog::Logger::root(drain.fuse(), o!());
+
     let data_dir = match matches
         .value_of("datadir")
         .and_then(|v| Some(PathBuf::from(v)))