mma: make external caller mostly use an ExternalRangeChange

pkg/kv/kvserver/allocator/mmaprototype/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
         "load.go",
         "memo_helper.go",
         "messages.go",
+        "range_change.go",
         "rebalance_advisor.go",
         "store_load_summary.go",
         "store_set.go",

pkg/kv/kvserver/allocator/mmaprototype/allocator.go

@@ -56,16 +56,16 @@ type Allocator interface {
 	// Calls to AdjustPendingChangeDisposition must be correctly sequenced with
 	// full state updates from the local node provided in
 	// ProcessNodeLoadResponse.
-	AdjustPendingChangeDisposition(change PendingRangeChange, success bool)
+	AdjustPendingChangeDisposition(change ExternalRangeChange, success bool)
 
 	// RegisterExternalChange informs this allocator about yet to complete
 	// changes to the cluster which were not initiated by this allocator. The
 	// ownership of all state inside change is handed off to the callee. If ok
-	// is true, the change was registered, and the caller should subsequently
-	// use the same change in a subsequent call to
+	// is true, the change was registered, and the caller is returned an
+	// ExternalRangeChange that it should subsequently use in a call to
 	// AdjustPendingChangeDisposition when the changes are completed, either
 	// successfully or not. If ok is false, the change was not registered.
-	RegisterExternalChange(change PendingRangeChange) (ok bool)
+	RegisterExternalChange(change PendingRangeChange) (_ ExternalRangeChange, ok bool)
 
 	// ComputeChanges is called periodically and frequently, say every 10s.
 	//
@@ -82,7 +82,7 @@ type Allocator interface {
 	// the allocator, to avoid re-proposing the same change and to make
 	// adjustments to the load.
 	ComputeChanges(
-		ctx context.Context, msg *StoreLeaseholderMsg, opts ChangeOptions) []PendingRangeChange
+		ctx context.Context, msg *StoreLeaseholderMsg, opts ChangeOptions) []ExternalRangeChange
 
 	// AdminRelocateOne is a helper for AdminRelocateRange.
 	//

pkg/kv/kvserver/allocator/mmaprototype/allocator_state.go

@@ -259,7 +259,7 @@ func (a *allocatorState) ProcessStoreLoadMsg(ctx context.Context, msg *StoreLoad
 }
 
 // AdjustPendingChangeDisposition implements the Allocator interface.
-func (a *allocatorState) AdjustPendingChangeDisposition(change PendingRangeChange, success bool) {
+func (a *allocatorState) AdjustPendingChangeDisposition(change ExternalRangeChange, success bool) {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	rs, ok := a.cs.ranges[change.RangeID]
@@ -279,7 +279,7 @@ func (a *allocatorState) AdjustPendingChangeDisposition(change PendingRangeChang
 	// can be made about whether these changes will be found in the allocator's
 	// state. We gather the found changes.
 	var changes []*pendingReplicaChange
-	for _, c := range change.pendingReplicaChanges {
+	for _, c := range change.Changes {
 		ch, ok := a.cs.pendingChanges[c.changeID]
 		if !ok {
 			continue
@@ -308,25 +308,27 @@ func (a *allocatorState) AdjustPendingChangeDisposition(change PendingRangeChang
 }
 
 // RegisterExternalChange implements the Allocator interface.
-func (a *allocatorState) RegisterExternalChange(change PendingRangeChange) (ok bool) {
+func (a *allocatorState) RegisterExternalChange(
+	change PendingRangeChange,
+) (_ ExternalRangeChange, ok bool) {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	if err := a.cs.preCheckOnApplyReplicaChanges(change); err != nil {
 		a.mmaMetrics.ExternalFailedToRegister.Inc(1)
 		log.KvDistribution.Infof(context.Background(),
 			"did not register external changes: due to %v", err)
-		return false
+		return ExternalRangeChange{}, false
 	} else {
 		a.mmaMetrics.ExternaRegisterSuccess.Inc(1)
 	}
 	a.cs.addPendingRangeChange(change)
-	return true
+	return MakeExternalRangeChange(change), true
 }
 
 // ComputeChanges implements the Allocator interface.
 func (a *allocatorState) ComputeChanges(
 	ctx context.Context, msg *StoreLeaseholderMsg, opts ChangeOptions,
-) []PendingRangeChange {
+) []ExternalRangeChange {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	if msg.StoreID != opts.LocalStoreID {