cleanup(gossip): Use a separate named constant for the gossip interval (#6704)

* Use a named consttant for the gossip interval

* Update tests

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

zebrad/src/components/inbound/tests/fake_peer_set.rs

@@ -35,7 +35,7 @@ use crate::{
             gossip_mempool_transaction_id, unmined_transactions_in_blocks, Config as MempoolConfig,
             Mempool, MempoolError, SameEffectsChainRejectionError, UnboxMempoolError,
         },
-        sync::{self, BlockGossipError, SyncStatus, TIPS_RESPONSE_TIMEOUT},
+        sync::{self, BlockGossipError, SyncStatus, PEER_GOSSIP_DELAY},
     },
     BoxError,
 };
@@ -421,7 +421,7 @@ async fn mempool_transaction_expiration() -> Result<(), crate::BoxError> {
     hs.insert(tx1_id);
 
     // Transaction and Block IDs are gossipped, in any order, after waiting for the gossip delay
-    tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+    tokio::time::sleep(PEER_GOSSIP_DELAY).await;
     let possible_requests = &mut [
         Request::AdvertiseTransactionIds(hs),
         Request::AdvertiseBlock(block_two.hash()),
@@ -490,7 +490,7 @@ async fn mempool_transaction_expiration() -> Result<(), crate::BoxError> {
         .unwrap();
 
     // Test the block is gossiped, after waiting for the multi-gossip delay
-    tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+    tokio::time::sleep(PEER_GOSSIP_DELAY).await;
     peer_set
         .expect_request(Request::AdvertiseBlock(block_three.hash()))
         .await
@@ -567,7 +567,7 @@ async fn mempool_transaction_expiration() -> Result<(), crate::BoxError> {
     );
 
     // Test transaction 2 is gossiped, after waiting for the multi-gossip delay
-    tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+    tokio::time::sleep(PEER_GOSSIP_DELAY).await;
 
     let mut hs = HashSet::new();
     hs.insert(tx2_id);
@@ -598,7 +598,7 @@ async fn mempool_transaction_expiration() -> Result<(), crate::BoxError> {
             .unwrap();
 
         // Test the block is gossiped, after waiting for the multi-gossip delay
-        tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+        tokio::time::sleep(PEER_GOSSIP_DELAY).await;
         peer_set
             .expect_request(Request::AdvertiseBlock(block.hash()))
             .await

zebrad/src/components/mempool/gossip.rs

@@ -16,7 +16,10 @@ use zebra_network::MAX_TX_INV_IN_SENT_MESSAGE;
 
 use zebra_network as zn;
 
-use crate::{components::sync::TIPS_RESPONSE_TIMEOUT, BoxError};
+use crate::{
+    components::sync::{PEER_GOSSIP_DELAY, TIPS_RESPONSE_TIMEOUT},
+    BoxError,
+};
 
 /// The maximum number of channel messages we will combine into a single peer broadcast.
 pub const MAX_CHANGES_BEFORE_SEND: usize = 10;
@@ -96,6 +99,6 @@ where
         //
         // in practice, transactions arrive every 1-20 seconds,
         // so waiting 6 seconds can delay transaction propagation, in order to reduce peer load
-        tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+        tokio::time::sleep(PEER_GOSSIP_DELAY).await;
     }
 }

zebrad/src/components/sync.rs

@@ -107,6 +107,16 @@ pub const MAX_TIPS_RESPONSE_HASH_COUNT: usize = 500;
 /// failure loop.
 pub const TIPS_RESPONSE_TIMEOUT: Duration = Duration::from_secs(6);
 
+/// Controls how long we wait between gossiping successive blocks or transactions.
+///
+/// ## Correctness
+///
+/// If this timeout is set too high, blocks and transactions won't propagate through
+/// the network efficiently.
+///
+/// If this timeout is set too low, the peer set and remote peers can get overloaded.
+pub const PEER_GOSSIP_DELAY: Duration = Duration::from_secs(7);
+
 /// Controls how long we wait for a block download request to complete.
 ///
 /// This timeout makes sure that the syncer doesn't hang when:

zebrad/src/components/sync/gossip.rs

@@ -9,9 +9,10 @@ use tower::{timeout::Timeout, Service, ServiceExt};
 use zebra_network as zn;
 use zebra_state::ChainTipChange;
 
-use crate::BoxError;
-
-use super::{SyncStatus, TIPS_RESPONSE_TIMEOUT};
+use crate::{
+    components::sync::{SyncStatus, PEER_GOSSIP_DELAY, TIPS_RESPONSE_TIMEOUT},
+    BoxError,
+};
 
 use BlockGossipError::*;
 
@@ -90,6 +91,6 @@ where
         //
         // in practice, we expect blocks to arrive approximately every 75 seconds,
         // so waiting 6 seconds won't make much difference
-        tokio::time::sleep(TIPS_RESPONSE_TIMEOUT).await;
+        tokio::time::sleep(PEER_GOSSIP_DELAY).await;
     }
 }