asim: sort map by key when iterating

While investigating #105904, we found that the bug's cause is due to the
simulator's iteration over an unordered map, leading to non-determinism. There
are other occurrences in the simulator's code where unordered map iteration
takes place. To make the code less error-prone, this patch checks the
simulator's code and sorts unordered maps by key when iterating. While it's
uncertain whether this change will solve any underlying non-determinism or
pinpoint exactly where in the code non-determinism might occur, there is no harm
in making the system less error-prone.

Part Of:#105904
Release Note: None

pkg/kv/kvserver/asim/event/delayed_event.go

@@ -24,6 +24,9 @@ func (del DelayedEventList) Len() int { return len(del) }
 
 // Less implements sort.Interface.
 func (del DelayedEventList) Less(i, j int) bool {
+	if del[i].At == del[j].At {
+		return i < j
+	}
 	return del[i].At.Before(del[j].At)
 }
 

pkg/kv/kvserver/asim/gossip/exchange.go

@@ -44,7 +44,12 @@ func (u *fixedDelayExchange) put(tick time.Time, descs ...roachpb.StoreDescripto
 // updates returns back exchanged infos, wrapped as store details that have
 // completed between the last tick update was called and the tick given.
 func (u *fixedDelayExchange) updates(tick time.Time) []*storepool.StoreDetail {
-	sort.Slice(u.pending, func(i, j int) bool { return u.pending[i].created.Before(u.pending[j].created) })
+	sort.Slice(u.pending, func(i, j int) bool {
+		if u.pending[i].created == u.pending[j].created {
+			return i < j
+		}
+		return u.pending[i].created.Before(u.pending[j].created)
+	})
 	ready := []*storepool.StoreDetail{}
 	i := 0
 	for ; i < len(u.pending) && !tick.Before(u.pending[i].created.Add(u.settings.StateExchangeDelay)); i++ {

pkg/kv/kvserver/asim/state/impl.go

@@ -178,7 +178,13 @@ func (s *state) ClusterInfo() ClusterInfo {
 // Stores returns all stores that exist in this state.
 func (s *state) Stores() []Store {
 	stores := make([]Store, 0, len(s.stores))
-	for _, store := range s.stores {
+	keys := make([]StoreID, 0, len(s.stores))
+	for key := range s.stores {
+		keys = append(keys, key)
+	}
+
+	for _, key := range keys {
+		store := s.stores[key]
 		stores = append(stores, store)
 	}
 	sort.Slice(stores, func(i, j int) bool { return stores[i].StoreID() < stores[j].StoreID() })
@@ -344,7 +350,12 @@ func (s *state) Replicas(storeID StoreID) []Replica {
 	}
 
 	repls := make(replicaList, 0, len(store.replicas))
+	var rangeIDs RangeIDSlice
 	for rangeID := range store.replicas {
+		rangeIDs = append(rangeIDs, rangeID)
+	}
+	sort.Sort(rangeIDs)
+	for _, rangeID := range rangeIDs {
 		rng := s.ranges.rangeMap[rangeID]
 		if replica := rng.replicas[storeID]; replica != nil {
 			repls = append(repls, replica)
@@ -1017,7 +1028,13 @@ func (s *state) TickClock(tick time.Time) {
 func (s *state) UpdateStorePool(
 	storeID StoreID, storeDescriptors map[roachpb.StoreID]*storepool.StoreDetail,
 ) {
-	for gossipStoreID, detail := range storeDescriptors {
+	var storeIDs roachpb.StoreIDSlice
+	for storeIDA := range storeDescriptors {
+		storeIDs = append(storeIDs, storeIDA)
+	}
+	sort.Sort(storeIDs)
+	for _, gossipStoreID := range storeIDs {
+		detail := storeDescriptors[gossipStoreID]
 		copiedDetail := *detail
 		copiedDesc := *detail.Desc
 		copiedDetail.Desc = &copiedDesc

pkg/kv/kvserver/asim/state/new_state.go

@@ -27,6 +27,9 @@ type requestCounts []requestCount
 
 func (s requestCounts) Len() int { return len(s) }
 func (s requestCounts) Less(i, j int) bool {
+	if s[i].req == s[j].req {
+		return i < j
+	}
 	return s[i].req > s[j].req
 }
 func (s requestCounts) Swap(i, j int) { s[i], s[j] = s[j], s[i] }

pkg/kv/kvserver/asim/state/state.go

@@ -36,6 +36,18 @@ type (
 	RangeID int32
 )
 
+type RangeIDSlice []RangeID
+
+func (r RangeIDSlice) Len() int           { return len(r) }
+func (r RangeIDSlice) Swap(i, j int)      { r[i], r[j] = r[j], r[i] }
+func (r RangeIDSlice) Less(i, j int) bool { return r[i] < r[j] }
+
+type StoreIDSlice []StoreID
+
+func (r StoreIDSlice) Len() int           { return len(r) }
+func (r StoreIDSlice) Swap(i, j int)      { r[i], r[j] = r[j], r[i] }
+func (r StoreIDSlice) Less(i, j int) bool { return r[i] < r[j] }
+
 // State encapsulates the current configuration and load of a simulation run.
 // It provides methods for accessing and mutation simulation state of nodes,
 // stores, ranges and replicas.

pkg/kv/kvserver/asim/tests/testdata/example_zone_config

@@ -55,22 +55,22 @@ plot stat=replicas
 ----
 ----
 
- 51.00 ┤               ╭╭──────────────────────────────────────────────────────────────
- 47.60 ┤           ╭╮╭─╭╯─────╯────────────────────────────────────────────────────────
- 44.20 ┤           │╭──╯
- 40.80 ┤          ╭╭╯╯
- 37.40 ┤         ╭─╯
- 34.00 ┤         │─╯
- 30.60 ┤         │╯
- 27.20 ┤        ╭│
- 23.80 ┤        ╭╯
- 20.40 ┤        │╯
- 17.00 ┼────────╮╮
- 13.60 ┤        ╰╮╮
- 10.20 ┤        ╰│╰╮╮
-  6.80 ┤         ╰─╮───╮
-  3.40 ┤         ╰╰╰───╮──────╮
-  0.00 ┤          ╰╰╰╰─╰───────────────────────────────────────────────────────────────
+ 52.00 ┤                 ╭╭────────────────────────────────────────────────────────────
+ 48.53 ┤            ╭╭─────────────────────────────────────────────────────────────────
+ 45.07 ┤          ╭╮││─╯╯
+ 41.60 ┤         ╭│╭─╯╯
+ 38.13 ┤         │││╯
+ 34.67 ┤         ╭╭╯
+ 31.20 ┤        ╭╭╯
+ 27.73 ┤        ││╯
+ 24.27 ┤        ││
+ 20.80 ┤       ╭╭╯
+ 17.33 ┼────────╮╮
+ 13.87 ┤       ╰╰╮╮╮
+ 10.40 ┤        ╰╰─╮╮
+  6.93 ┤         ╰╰╰──╮
+  3.47 ┤         ╰╰╰╰─╰────╮
+  0.00 ┤          ╰╰─╰╰────╰───────────────────────────────────────────────────────────
                                             replicas
 ----
 ----