Add graffiti cli flag to the validator client. (#1425)

## Issue Addressed

#1419

## Proposed Changes

Creates a `--graffiti` cli flag in the validator client. If the flag is set, it overrides graffiti in the beacon node. 

## Additional Info

validator_client/src/block_service.rs

@@ -7,7 +7,7 @@ use slog::{crit, debug, error, info, trace, warn};
 use slot_clock::SlotClock;
 use std::ops::Deref;
 use std::sync::Arc;
-use types::{EthSpec, PublicKey, Slot};
+use types::{EthSpec, Graffiti, PublicKey, Slot};
 
 /// Builds a `BlockService`.
 pub struct BlockServiceBuilder<T, E: EthSpec> {
@@ -15,6 +15,7 @@ pub struct BlockServiceBuilder<T, E: EthSpec> {
     slot_clock: Option<Arc<T>>,
     beacon_node: Option<RemoteBeaconNode<E>>,
     context: Option<RuntimeContext<E>>,
+    graffiti: Option<Graffiti>,
 }
 
 impl<T: SlotClock + 'static, E: EthSpec> BlockServiceBuilder<T, E> {
@@ -24,6 +25,7 @@ impl<T: SlotClock + 'static, E: EthSpec> BlockServiceBuilder<T, E> {
             slot_clock: None,
             beacon_node: None,
             context: None,
+            graffiti: None,
         }
     }
 
@@ -47,6 +49,11 @@ impl<T: SlotClock + 'static, E: EthSpec> BlockServiceBuilder<T, E> {
         self
     }
 
+    pub fn graffiti(mut self, graffiti: Option<Graffiti>) -> Self {
+        self.graffiti = graffiti;
+        self
+    }
+
     pub fn build(self) -> Result<BlockService<T, E>, String> {
         Ok(BlockService {
             inner: Arc::new(Inner {
@@ -62,6 +69,7 @@ impl<T: SlotClock + 'static, E: EthSpec> BlockServiceBuilder<T, E> {
                 context: self
                     .context
                     .ok_or_else(|| "Cannot build BlockService without runtime_context")?,
+                graffiti: self.graffiti,
             }),
         })
     }
@@ -73,6 +81,7 @@ pub struct Inner<T, E: EthSpec> {
     slot_clock: Arc<T>,
     beacon_node: RemoteBeaconNode<E>,
     context: RuntimeContext<E>,
+    graffiti: Option<Graffiti>,
 }
 
 /// Attempts to produce attestations for any block producer(s) at the start of the epoch.
@@ -214,7 +223,7 @@ impl<T: SlotClock + 'static, E: EthSpec> BlockService<T, E> {
             .beacon_node
             .http
             .validator()
-            .produce_block(slot, randao_reveal)
+            .produce_block(slot, randao_reveal, self.graffiti)
             .await
             .map_err(|e| format!("Error from beacon node when producing block: {:?}", e))?;
 

validator_client/src/cli.rs

@@ -60,4 +60,12 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                       node is not synced.",
                 ),
         )
+        // This overwrites the graffiti configured in the beacon node.
+        .arg(
+            Arg::with_name("graffiti")
+                .long("graffiti")
+                .help("Specify your custom graffiti to be included in blocks.")
+                .value_name("GRAFFITI")
+                .takes_value(true)
+        )
 }

validator_client/src/config.rs

@@ -2,6 +2,7 @@ use clap::ArgMatches;
 use clap_utils::{parse_optional, parse_path_with_default_in_home_dir};
 use serde_derive::{Deserialize, Serialize};
 use std::path::PathBuf;
+use types::{Graffiti, GRAFFITI_BYTES_LEN};
 
 pub const DEFAULT_HTTP_SERVER: &str = "http://localhost:5052/";
 pub const DEFAULT_DATA_DIR: &str = ".lighthouse/validators";
@@ -27,6 +28,8 @@ pub struct Config {
     pub strict_lockfiles: bool,
     /// If true, don't scan the validators dir for new keystores.
     pub disable_auto_discover: bool,
+    /// Graffiti to be inserted everytime we create a block.
+    pub graffiti: Option<Graffiti>,
 }
 
 impl Default for Config {
@@ -45,6 +48,7 @@ impl Default for Config {
             allow_unsynced_beacon_node: false,
             strict_lockfiles: false,
             disable_auto_discover: false,
+            graffiti: None,
         }
     }
 }
@@ -80,6 +84,26 @@ impl Config {
             config.secrets_dir = secrets_dir;
         }
 
+        if let Some(input_graffiti) = cli_args.value_of("graffiti") {
+            let graffiti_bytes = input_graffiti.as_bytes();
+            if graffiti_bytes.len() > GRAFFITI_BYTES_LEN {
+                return Err(format!(
+                    "Your graffiti is too long! {} bytes maximum!",
+                    GRAFFITI_BYTES_LEN
+                ));
+            } else {
+                // Default graffiti to all 0 bytes.
+                let mut graffiti = Graffiti::default();
+
+                // Copy the provided bytes over.
+                //
+                // Panic-free because `graffiti_bytes.len()` <= `GRAFFITI_BYTES_LEN`.
+                graffiti[..graffiti_bytes.len()].copy_from_slice(&graffiti_bytes);
+
+                config.graffiti = Some(graffiti);
+            }
+        }
+
         Ok(config)
     }
 }

validator_client/src/lib.rs

@@ -216,6 +216,7 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
             .validator_store(validator_store.clone())
             .beacon_node(beacon_node.clone())
             .runtime_context(context.service_context("block".into()))
+            .graffiti(config.graffiti)
             .build()?;
 
         let attestation_service = AttestationServiceBuilder::new()