kuma-cp: add a custom version of SnapshotCache that supports arbitrar…

…y xDS resources

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 Changes:
 
+* feature: add a custom version of SnapshotCache that supports arbitrary xDS resources
+  [#528](https://github.com/Kong/kuma/pull/528)
 * feature: add proto definition for Monitoring Assignment Discovery Service (MADS)
   [#525](https://github.com/Kong/kuma/pull/525)
 * feature: enable Envoy Admin API by default with an option to opt out

pkg/mads/cache/snapshot.go

@@ -0,0 +1,73 @@
+package server
+
+import (
+	"github.com/pkg/errors"
+
+	envoy_cache "github.com/envoyproxy/go-control-plane/pkg/cache"
+
+	"github.com/Kong/kuma/pkg/mads"
+	util_xds "github.com/Kong/kuma/pkg/util/xds"
+)
+
+// NewSnapshot creates a snapshot from response types and a version.
+func NewSnapshot(version string, assignments []envoy_cache.Resource) Snapshot {
+	return Snapshot{
+		MonitoringAssignments: envoy_cache.NewResources(version, assignments),
+	}
+}
+
+// Snapshot is an internally consistent snapshot of xDS resources.
+type Snapshot struct {
+	MonitoringAssignments envoy_cache.Resources
+}
+
+var _ util_xds.Snapshot = &Snapshot{}
+
+// GetSupportedTypes returns a list of xDS types supported by this snapshot.
+func (s *Snapshot) GetSupportedTypes() []string {
+	return []string{mads.MonitoringAssignmentType}
+}
+
+// Consistent check verifies that the dependent resources are exactly listed in the
+// snapshot.
+func (s *Snapshot) Consistent() error {
+	if s == nil {
+		return errors.New("nil snapshot")
+	}
+	return nil
+}
+
+// GetResources selects snapshot resources by type.
+func (s *Snapshot) GetResources(typ string) map[string]envoy_cache.Resource {
+	if s == nil {
+		return nil
+	}
+	switch typ {
+	case mads.MonitoringAssignmentType:
+		return s.MonitoringAssignments.Items
+	}
+	return nil
+}
+
+// GetVersion returns the version for a resource type.
+func (s *Snapshot) GetVersion(typ string) string {
+	if s == nil {
+		return ""
+	}
+	switch typ {
+	case mads.MonitoringAssignmentType:
+		return s.MonitoringAssignments.Version
+	}
+	return ""
+}
+
+// SetVersion sets the version for a resource type.
+func (s *Snapshot) SetVersion(typ string, version string) {
+	if s == nil {
+		return
+	}
+	switch typ {
+	case mads.MonitoringAssignmentType:
+		s.MonitoringAssignments.Version = version
+	}
+}

pkg/mads/types.go

@@ -0,0 +1,5 @@
+package mads
+
+const (
+	MonitoringAssignmentType = "type.googleapis.com/kuma.observability.v1alpha1.MonitoringAssignment"
+)