Companion for https://github.com/paritytech/substrate/pull/13725 (#2401)

* Companion for https://github.com/paritytech/substrate/pull/13725

* Add comment

* update lockfile for {"substrate", "polkadot"}

---------

Co-authored-by: parity-processbot <>

cumulus/client/relay-chain-minimal-node/Cargo.toml

@@ -21,6 +21,7 @@ sc-network = { git = "https://github.com/paritytech/substrate", branch = "master
 sc-network-common = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-service = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-tracing = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sc-utils = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-api = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-blockchain = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-consensus-babe = { git = "https://github.com/paritytech/substrate", branch = "master" }

cumulus/client/relay-chain-minimal-node/src/network.rs

@@ -26,6 +26,7 @@ use sc_network::{
 
 use sc_network_common::{role::Roles, sync::message::BlockAnnouncesHandshake};
 use sc_service::{error::Error, Configuration, NetworkStarter, SpawnTaskHandle};
+use sc_utils::mpsc::tracing_unbounded;
 
 use std::{iter, sync::Arc};
 
@@ -49,6 +50,8 @@ pub(crate) fn build_collator_network(
 		genesis_hash,
 	);
 
+	// RX is not used for anything because syncing is not started for the minimal node
+	let (tx, _rx) = tracing_unbounded("mpsc_syncing_engine_protocol", 100_000);
 	let network_params = sc_network::config::Params::<Block> {
 		role: config.role.clone(),
 		executor: {
@@ -64,6 +67,7 @@ pub(crate) fn build_collator_network(
 		metrics_registry: config.prometheus_config.as_ref().map(|config| config.registry.clone()),
 		block_announce_config,
 		request_response_protocol_configs: Vec::new(),
+		tx,
 	};
 
 	let network_worker = sc_network::NetworkWorker::new(network_params)?;