Support dependency/redundancy group state checksum on the fly

pkg/contracts/contracts.go

@@ -27,3 +27,10 @@ func SafeInit(v any) {
 		initer.Init()
 	}
 }
+
+// Equaler is implemented by any entity that can be compared with another entity of the same type.
+// The Equal method should return true if the receiver is equal to the other entity.
+type Equaler interface {
+	// Equal returns whether the receiver is equal to the other entity.
+	Equal(other any) bool
+}

pkg/icingadb/delta.go

@@ -53,7 +53,7 @@ func (delta *Delta) run(ctx context.Context, actualCh, desiredCh <-chan database
 	desired := EntitiesById{} // only read from desiredCh (so far)
 
 	var update EntitiesById
-	if delta.Subject.WithChecksum() {
+	if _, ok := delta.Subject.Entity().(contracts.Equaler); ok || delta.Subject.WithChecksum() {
 		update = EntitiesById{} // read from actualCh and desiredCh with mismatching checksums
 	}
 
@@ -120,5 +120,9 @@ func (delta *Delta) run(ctx context.Context, actualCh, desiredCh <-chan database
 // checksumsMatch returns whether the checksums of two entities are the same.
 // Both entities must implement contracts.Checksumer.
 func checksumsMatch(a, b database.Entity) bool {
-	return cmp.Equal(a.(contracts.Checksumer).Checksum(), b.(contracts.Checksumer).Checksum())
+	if _, ok := a.(contracts.Checksumer); ok {
+		return cmp.Equal(a.(contracts.Checksumer).Checksum(), b.(contracts.Checksumer).Checksum())
+	}
+
+	return a.(contracts.Equaler).Equal(b)
 }

pkg/icingadb/sync.go

@@ -148,9 +148,18 @@ func (s Sync) ApplyDelta(ctx context.Context, delta *Delta) error {
 		entitiesWithoutChecksum, errs := icingaredis.CreateEntities(ctx, delta.Subject.Factory(), pairs, runtime.NumCPU())
 		// Let errors from CreateEntities cancel our group.
 		com.ErrgroupReceive(g, errs)
-		entities, errs := icingaredis.SetChecksums(ctx, entitiesWithoutChecksum, delta.Update, runtime.NumCPU())
-		// Let errors from SetChecksums cancel our group.
-		com.ErrgroupReceive(g, errs)
+
+		var entities <-chan database.Entity
+		// Apply the checksums only if the sync subject supports it, i.e, it implements contracts.Checksumer.
+		// This is necessary because not only entities that implement contracts.Checksumer can be updated, but
+		// also entities that implement contracts.Equaler interface.
+		if delta.Subject.WithChecksum() {
+			entities, errs = icingaredis.SetChecksums(ctx, entitiesWithoutChecksum, delta.Update, runtime.NumCPU())
+			// Let errors from SetChecksums cancel our group.
+			com.ErrgroupReceive(g, errs)
+		} else {
+			entities = entitiesWithoutChecksum
+		}
 
 		g.Go(func() error {
 			// Using upsert here on purpose as this is the fastest way to do bulk updates.

pkg/icingadb/v1/dependency.go

@@ -1,6 +1,8 @@
 package v1
 
 import (
+	"bytes"
+	"github.com/google/go-cmp/cmp"
 	"github.com/icinga/icinga-go-library/database"
 	"github.com/icinga/icinga-go-library/types"
 )
@@ -30,6 +32,18 @@ func (r RedundancygroupState) TableName() string {
 	return "redundancy_group_state"
 }
 
+// Equal implements the [contracts.Equaler] interface.
+func (r RedundancygroupState) Equal(other any) bool {
+	if other, ok := other.(*RedundancygroupState); ok {
+		return bytes.Equal(r.RedundancyGroupId, other.RedundancyGroupId) &&
+			cmp.Equal(r.Failed, other.Failed) &&
+			cmp.Equal(r.IsReachable, other.IsReachable) &&
+			r.LastStateChange.Time().Equal(other.LastStateChange.Time())
+	}
+
+	return false
+}
+
 type DependencyNode struct {
 	EntityWithoutChecksum `json:",inline"`
 	EnvironmentMeta       `json:",inline"`
@@ -44,6 +58,15 @@ type DependencyEdgeState struct {
 	Failed                types.Bool `json:"failed"`
 }
 
+// Equal implements the [contracts.Equaler] interface.
+func (es DependencyEdgeState) Equal(other any) bool {
+	if other, ok := other.(*DependencyEdgeState); ok {
+		return bytes.Equal(es.Id, other.Id) && cmp.Equal(es.Failed, other.Failed)
+	}
+
+	return false
+}
+
 type DependencyEdge struct {
 	EntityWithoutChecksum `json:",inline"`
 	EnvironmentMeta       `json:",inline"`