feat(nns): Move spawn_neurons to a one-minute timer

rs/nns/governance/canister/canister.rs

@@ -165,6 +165,7 @@ fn schedule_timers() {
     schedule_seeding(Duration::from_nanos(0));
     schedule_adjust_neurons_storage(Duration::from_nanos(0), NeuronIdProto { id: 0 });
     schedule_prune_following(Duration::from_secs(0));
+    schedule_spawn_neurons();
 }
 
 // Seeding interval seeks to find a balance between the need for rng secrecy, and
@@ -268,6 +269,16 @@ fn schedule_adjust_neurons_storage(delay: Duration, start_neuron_id: NeuronIdPro
     });
 }
 
+const SPAWN_NEURONS_INTERVAL: Duration = Duration::from_secs(60);
+
+fn schedule_spawn_neurons() {
+    ic_cdk_timers::set_timer_interval(SPAWN_NEURONS_INTERVAL, || {
+        spawn(async {
+            governance_mut().maybe_spawn_neurons().await;
+        });
+    });
+}
+
 struct CanisterEnv {
     rng: Option<ChaCha20Rng>,
     time_warp: GovTimeWarp,

rs/nns/governance/src/governance.rs

@@ -6558,9 +6558,6 @@ impl Governance {
         // Try to update maturity modulation (once per day).
         } else if self.should_update_maturity_modulation() {
             self.update_maturity_modulation().await;
-        // Try to spawn neurons (potentially multiple times per day).
-        } else if self.can_spawn_neurons() {
-            self.spawn_neurons().await;
         } else {
             // This is the lowest-priority async task. All other tasks should have their own
             // `else if`, like the ones above.
@@ -6702,7 +6699,7 @@ impl Governance {
     /// This means that programming in this method needs to be extra-defensive on the handling of results so that
     /// we're sure not to trap after we've acquired the global lock and made an async call, as otherwise the global
     /// lock will be permanently held and no spawning will occur until a upgrade to fix it is made.
-    async fn spawn_neurons(&mut self) {
+    pub async fn maybe_spawn_neurons(&mut self) {
         if !self.can_spawn_neurons() {
             return;
         }

rs/nns/governance/tests/governance.rs

@@ -5737,7 +5737,7 @@ fn test_seed_neuron_split() {
 
 // Spawn neurons has the least priority in the periodic tasks, so we need to run
 // them often enough to make sure it happens.
-fn run_periodic_tasks_on_governance_often_enough_to_spawn(gov: &mut Governance) {
+fn run_periodic_tasks_often_enough_to_update_maturity_modulation(gov: &mut Governance) {
     for _i in 0..5 {
         gov.run_periodic_tasks().now_or_never();
     }
@@ -5766,6 +5766,7 @@ fn test_neuron_spawn() {
         from,
         nonce,
     );
+    run_periodic_tasks_often_enough_to_update_maturity_modulation(&mut gov);
 
     let now = driver.now();
     assert_eq!(
@@ -5898,13 +5899,13 @@ fn test_neuron_spawn() {
     let creation_timestamp = driver.now();
 
     // Running periodic tasks shouldn't cause the ICP to be minted.
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(1);
 
     // Advance the time by one week, should cause the neuron's ICP
     // to be minted.
     driver.advance_time_by(7 * 86400);
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(2);
 
     let child_neuron = gov
@@ -5953,6 +5954,7 @@ fn test_neuron_spawn_with_subaccount() {
         from,
         nonce,
     );
+    run_periodic_tasks_often_enough_to_update_maturity_modulation(&mut gov);
 
     let now = driver.now();
     assert_eq!(
@@ -6035,7 +6037,7 @@ fn test_neuron_spawn_with_subaccount() {
     driver.assert_num_neuron_accounts_exist(1);
 
     // Running periodic tasks shouldn't cause the ICP to be minted.
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(1);
 
     let parent_neuron = gov
@@ -6047,7 +6049,7 @@ fn test_neuron_spawn_with_subaccount() {
     // Advance the time by one week, should cause the neuron's ICP
     // to be minted.
     driver.advance_time_by(7 * 86400);
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(2);
 
     let child_neuron = gov
@@ -6132,6 +6134,7 @@ fn assert_neuron_spawn_partial(
         from,
         nonce,
     );
+    run_periodic_tasks_often_enough_to_update_maturity_modulation(&mut gov);
 
     let neuron = gov
         .with_neuron(&id, |neuron| neuron.clone())
@@ -6193,7 +6196,7 @@ fn assert_neuron_spawn_partial(
         .expect("The parent neuron is missing");
 
     // Running periodic tasks shouldn't cause the ICP to be minted.
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(1);
 
     // Some maturity should be remaining on the parent neuron.
@@ -6205,7 +6208,7 @@ fn assert_neuron_spawn_partial(
     // Advance the time by one week, should cause the neuron's ICP
     // to be minted.
     driver.advance_time_by(7 * 86400);
-    run_periodic_tasks_on_governance_often_enough_to_spawn(&mut gov);
+    gov.maybe_spawn_neurons().now_or_never().unwrap();
     driver.assert_num_neuron_accounts_exist(2);
 
     let child_neuron = gov