Refactor attestation service (#1415)

## Issue Addressed

N/A

## Proposed Changes

Refactor attestation service to send out requests to find peers for subnets as soon as we get attestation duties. 
Earlier, we had much more involved logic to send the discovery requests to the discovery service only 6 slots before the attestation slot. Now that discovery is much smarter with grouped queries, the complexity in attestation service can be reduced considerably.



Co-authored-by: Age Manning <Age@AgeManning.com>

beacon_node/eth2_libp2p/src/discovery/mod.rs

@@ -8,7 +8,7 @@ pub use enr_ext::{CombinedKeyExt, EnrExt};
 pub use libp2p::core::identity::Keypair;
 
 use crate::metrics;
-use crate::{error, Enr, NetworkConfig, NetworkGlobals};
+use crate::{error, Enr, NetworkConfig, NetworkGlobals, SubnetDiscovery};
 use discv5::{enr::NodeId, Discv5, Discv5Event};
 use enr::{BITFIELD_ENR_KEY, ETH2_ENR_KEY};
 use futures::prelude::*;
@@ -305,12 +305,19 @@ impl<TSpec: EthSpec> Discovery<TSpec> {
     }
 
     /// Processes a request to search for more peers on a subnet.
-    pub fn discover_subnet_peers(&mut self, subnet_id: SubnetId, min_ttl: Option<Instant>) {
+    pub fn discover_subnet_peers(&mut self, subnets_to_discover: Vec<SubnetDiscovery>) {
         // If the discv5 service isn't running, ignore queries
         if !self.started {
             return;
         }
-        self.add_subnet_query(subnet_id, min_ttl, 0);
+        debug!(
+            self.log,
+            "Making discovery query for subnets";
+            "subnets" => format!("{:?}", subnets_to_discover.iter().map(|s| s.subnet_id).collect::<Vec<_>>())
+        );
+        for subnet in subnets_to_discover {
+            self.add_subnet_query(subnet.subnet_id, subnet.min_ttl, 0);
+        }
     }
 
     /// Add an ENR to the routing table of the discovery mechanism.
@@ -514,6 +521,11 @@ impl<TSpec: EthSpec> Discovery<TSpec> {
                         // This query is for searching for peers of a particular subnet
                         // Drain subnet_queries so we can re-use it as we continue to process the queue
                         let grouped_queries: Vec<SubnetQuery> = subnet_queries.drain(..).collect();
+                        debug!(
+                            self.log,
+                            "Starting grouped subnet query";
+                            "subnets" => format!("{:?}", grouped_queries.iter().map(|q| q.subnet_id).collect::<Vec<_>>()),
+                        );
                         self.start_subnet_query(grouped_queries);
                     }
                 }

beacon_node/eth2_libp2p/src/discovery/subnet_predicate.rs

@@ -1,5 +1,6 @@
 ///! The subnet predicate used for searching for a particular subnet.
 use super::*;
+use slog::{debug, trace};
 use std::ops::Deref;
 
 /// Returns the predicate for a given subnet.
@@ -30,7 +31,7 @@ where
                 .collect();
 
             if matches.is_empty() {
-                debug!(
+                trace!(
                     log_clone,
                     "Peer found but not on any of the desired subnets";
                     "peer_id" => format!("{}", enr.peer_id())