add global constant for how many queues an OpSubmitter has

rust/main/agents/relayer/src/msg/op_queue.rs

@@ -72,7 +72,6 @@ impl OpQueue {
         // The other consideration is whether to put the channel receiver in the OpQueue or in a dedicated task
         // that also holds an Arc to the Mutex. For simplicity, we'll put it in the OpQueue for now.
         let mut message_retry_requests = vec![];
-        // we only need to lock self.retry_receiver once
         {
             let mut retry_receiver = self.retry_receiver.lock().await;
             while let Ok(retry_request) = retry_receiver.try_recv() {

rust/main/agents/relayer/src/msg/op_submitter.rs

@@ -37,6 +37,8 @@ use crate::server::MessageRetryRequest;
 use super::op_queue::OpQueue;
 use super::op_queue::OperationPriorityQueue;
 
+pub const SUBMITTER_QUEUE_COUNT: usize = 3;
+
 /// SerialSubmitter accepts operations over a channel. It is responsible for
 /// executing the right strategy to deliver those messages to the destination
 /// chain. It is designed to be used in a scenario allowing only one

rust/main/agents/relayer/src/server/message_retry.rs

@@ -1,6 +1,6 @@
 use std::sync::Arc;
 
-use crate::settings::matching_list::MatchingList;
+use crate::{msg::op_submitter::SUBMITTER_QUEUE_COUNT, settings::matching_list::MatchingList};
 use axum::{extract::State, routing, Json, Router};
 use derive_new::new;
 use serde::{Deserialize, Serialize};
@@ -52,7 +52,8 @@ async fn retry_message(
     // Create a channel that can hold each chain's SerialSubmitter
     // message retry responses.
     // 3 queues for each chain (prepare, submit, confirm)
-    let (transmitter, mut receiver) = mpsc::channel(3 * state.destination_chains);
+    let (transmitter, mut receiver) =
+        mpsc::channel(SUBMITTER_QUEUE_COUNT * state.destination_chains);
     state
         .retry_request_transmitter
         .send(Arc::new(MessageRetryRequest {