node: Address issues and PR comments

- Use request_block_by_height to initialize a presync procedure
- Update default hops_limit to 128
- Update DEFAULT_CERT_CACHE_EXPIRY to 1min
- Fix the condition for detecting sync target is reached

node/src/chain/fsm.rs

@@ -12,7 +12,10 @@ use crate::{vm, Network};
 use crate::database::{Candidate, Ledger};
 use metrics::counter;
 use node_data::ledger::{to_str, Block, Certificate, Label};
-use node_data::message::payload::{GetBlocks, Inv, RatificationResult, Vote};
+use node_data::message::payload::{
+    GetBlocks, GetResource, Inv, RatificationResult, Vote,
+};
+
 use node_data::message::{payload, Message, Metadata};
 use std::borrow::Cow;
 use std::collections::{HashMap, HashSet};
@@ -26,8 +29,8 @@ use tracing::{debug, error, info, warn};
 
 const MAX_BLOCKS_TO_REQUEST: i16 = 50;
 const EXPIRY_TIMEOUT_MILLIS: i16 = 5000;
-const DEFAULT_HOPS_LIMIT: u16 = 100;
-const DEFAULT_CERT_CACHE_EXPIRY: Duration = Duration::from_secs(10);
+const DEFAULT_CERT_CACHE_EXPIRY: Duration = Duration::from_secs(60);
+const DEFAULT_HOPS_LIMIT: u16 = 128;
 pub(crate) const REDUNDANCY_PEER_FACTOR: usize = 5;
 
 type SharedHashSet = Arc<RwLock<HashSet<[u8; 32]>>>;
@@ -167,7 +170,7 @@ impl<N: Network, DB: database::DB, VM: vm::VMExecution> SimpleFSM<N, DB, VM> {
             return Ok(());
         }
 
-        if let Some(blk) = self.get_block_with_cert(blk).as_ref() {
+        if let Some(blk) = self.attach_cert_if_needed(blk).as_ref() {
             match &mut self.curr {
                 State::InSync(ref mut curr) => {
                     if let Some((b, peer_addr)) =
@@ -206,6 +209,7 @@ impl<N: Network, DB: database::DB, VM: vm::VMExecution> SimpleFSM<N, DB, VM> {
             }
         }
 
+        // Clean up certificate cache
         let now = Instant::now();
         self.certificates_cache
             .retain(|_, (_, expiry)| *expiry > now);
@@ -215,6 +219,10 @@ impl<N: Network, DB: database::DB, VM: vm::VMExecution> SimpleFSM<N, DB, VM> {
     }
 
     async fn request_block(&mut self, hash: [u8; 32], cert: Certificate) {
+        if self.certificates_cache.contains_key(&hash) {
+            return;
+        }
+
         // Save certificate in case only candidate block is received
         let expiry = Instant::now()
             .checked_add(DEFAULT_CERT_CACHE_EXPIRY)
@@ -345,7 +353,7 @@ impl<N: Network, DB: database::DB, VM: vm::VMExecution> SimpleFSM<N, DB, VM> {
     }
 
     /// Try to attach the certificate to a block that misses it
-    fn get_block_with_cert<'a>(
+    fn attach_cert_if_needed<'a>(
         &self,
         blk: &'a Block,
     ) -> Option<Cow<'a, Block>> {
@@ -615,14 +623,39 @@ impl<DB: database::DB, VM: vm::VMExecution, N: Network> InSyncImpl<DB, VM, N> {
                 ));
             }
 
-            let mut inv = Inv::new(1);
-            inv.add_block_from_height(local_header.height + 1);
-            flood_request(&self.network, &inv).await;
+            Self::request_block_by_height(
+                &self.network,
+                local_header.height + 1,
+                metadata.src_addr,
+            )
+            .await;
         }
 
         Ok(None)
     }
 
+    /// Requests a block by height from a `peer_addr`
+    async fn request_block_by_height(
+        network: &Arc<RwLock<N>>,
+        height: u64,
+        peer_addr: SocketAddr,
+    ) {
+        let mut inv = Inv::new(1);
+        inv.add_block_from_height(height);
+        let this_peer = *network.read().await.public_addr();
+        let req = GetResource::new(inv, this_peer, u64::MAX, 1);
+        debug!(event = "request block by height", ?req, ?peer_addr);
+
+        if let Err(err) = network
+            .read()
+            .await
+            .send_to_peer(&Message::new_get_resource(req), peer_addr)
+            .await
+        {
+            warn!("could not request block {err}")
+        }
+    }
+
     async fn on_heartbeat(&mut self) -> anyhow::Result<bool> {
         // TODO: Consider reporting metrics here
 
@@ -761,10 +794,12 @@ impl<DB: database::DB, VM: vm::VMExecution, N: Network>
                 }
             }
 
+            let tip = acc.get_curr_height().await;
             // Check target height is reached
-            if acc.get_curr_height().await == self.range.1 {
+            if tip >= self.range.1 {
+                debug!(event = "sync target reached", height = tip);
+
                 // Block sync-up procedure manages to download all requested
-                // blocks
                 acc.restart_consensus().await;
 
                 // Transit to InSync mode
@@ -792,6 +827,7 @@ impl<DB: database::DB, VM: vm::VMExecution, N: Network>
             .unwrap()
             <= SystemTime::now()
         {
+            debug!(event = "out_of_sync timer expired");
             // sync-up has timed out, recover consensus task
             self.acc.write().await.restart_consensus().await;
 
@@ -807,6 +843,7 @@ impl<DB: database::DB, VM: vm::VMExecution, N: Network>
 /// Flood-request approach.
 async fn flood_request<N: Network>(network: &Arc<RwLock<N>>, inv: &Inv) {
     debug!(event = "flood_request", ?inv);
+
     if let Err(err) = network
         .read()
         .await