xds controller: resolve ServiceEndpoints references in ProxyStateTemp…

…late

internal/mesh/internal/controllers/xds/controller.go

@@ -0,0 +1,156 @@
+package xds
+
+import (
+	"context"
+
+	"github.com/hashicorp/consul/internal/catalog"
+	"github.com/hashicorp/consul/internal/controller"
+	"github.com/hashicorp/consul/internal/mesh/internal/controllers/xds/status"
+	"github.com/hashicorp/consul/internal/mesh/internal/types"
+	"github.com/hashicorp/consul/internal/resource"
+	"github.com/hashicorp/consul/internal/resource/mappers/bimapper"
+	pbmesh "github.com/hashicorp/consul/proto-public/pbmesh/v1alpha1"
+	"github.com/hashicorp/consul/proto-public/pbmesh/v1alpha1/pbproxystate"
+	"github.com/hashicorp/consul/proto-public/pbresource"
+)
+
+const ControllerName = "consul.io/xds-controller"
+
+func Controller(mapper *bimapper.Mapper, updater ProxyUpdater) controller.Controller {
+	if mapper == nil || updater == nil {
+		panic("mapper and updater are required")
+	}
+
+	return controller.ForType(types.ProxyStateTemplateType).
+		WithWatch(catalog.ServiceEndpointsType, mapper.MapLink).
+		WithPlacement(controller.PlacementEachServer).
+		WithReconciler(&xdsReconciler{bimapper: mapper, updater: updater})
+}
+
+type xdsReconciler struct {
+	bimapper *bimapper.Mapper
+	updater  ProxyUpdater
+}
+
+// ProxyUpdater is an interface that defines the ability to push proxy updates to the updater
+// and also check its connectivity to the server.
+type ProxyUpdater interface {
+	// PushChange allows pushing a computed ProxyState to xds for xds resource generation to send to a proxy.
+	PushChange(id *pbresource.ID, snapshot *pbmesh.ProxyState) error
+
+	// ProxyConnectedToServer returns whether this id is connected to this server.
+	ProxyConnectedToServer(id *pbresource.ID) bool
+}
+
+func (r *xdsReconciler) Reconcile(ctx context.Context, rt controller.Runtime, req controller.Request) error {
+	rt.Logger = rt.Logger.With("resource-id", req.ID, "controller", ControllerName)
+
+	rt.Logger.Trace("reconciling  proxy state template", "id", req.ID)
+
+	// Get the ProxyStateTemplate.
+	proxyStateTemplate, err := getProxyStateTemplate(ctx, rt, req.ID)
+	if err != nil {
+		rt.Logger.Error("error reading proxy state template", "error", err)
+		return err
+	}
+
+	if proxyStateTemplate == nil || proxyStateTemplate.Template == nil || !r.updater.ProxyConnectedToServer(req.ID) {
+		rt.Logger.Trace("proxy state template has been deleted or this controller is not responsible for this proxy state template", "id", req.ID)
+
+		// If the proxy state was deleted, we should remove references to it in the mapper.
+		r.bimapper.UntrackItem(req.ID)
+
+		return nil
+	}
+
+	var (
+		statusCondition *pbresource.Condition
+		pstResource     *pbresource.Resource
+	)
+	pstResource = proxyStateTemplate.Resource
+
+	// Initialize the ProxyState endpoints map.
+	if proxyStateTemplate.Template.ProxyState == nil {
+		rt.Logger.Error("proxy state was missing from proxy state template")
+		// Set the status.
+		statusCondition = status.ConditionRejectedNilProxyState(status.KeyFromID(req.ID))
+		status.WriteStatusIfChanged(ctx, rt, pstResource, statusCondition)
+
+		return err
+	}
+	if proxyStateTemplate.Template.ProxyState.Endpoints == nil {
+		proxyStateTemplate.Template.ProxyState.Endpoints = make(map[string]*pbproxystate.Endpoints)
+	}
+
+	// Iterate through the endpoint references.
+	// For endpoints, the controller should:
+	//  1. Resolve ServiceEndpoint references
+	//  2. Translate them into pbproxystate.Endpoints
+	//  3. Add the pbproxystate.Endpoints to the ProxyState endpoints map.
+	//  4. Track relationships between ProxyState and ServiceEndpoints, such that we can look up ServiceEndpoints and
+	//  figure out which ProxyStates are associated with it (for mapping watches) and vice versa (for looking up
+	//  references). The bimapper package is useful for tracking these relationships.
+	endpointReferencesMap := proxyStateTemplate.Template.RequiredEndpoints
+	var endpointsInProxyStateTemplate []resource.ReferenceOrID
+	for xdsClusterName, endpointRef := range endpointReferencesMap {
+
+		// Step 1: Resolve the reference by looking up the ServiceEndpoints.
+		// serviceEndpoints will not be nil unless there is an error.
+		serviceEndpoints, err := getServiceEndpoints(ctx, rt, endpointRef.Id)
+		if err != nil {
+			rt.Logger.Error("error reading service endpoint", "id", endpointRef.Id, "error", err)
+			// Set the status.
+			statusCondition = status.ConditionRejectedErrorReadingEndpoints(status.KeyFromID(endpointRef.Id), err.Error())
+			status.WriteStatusIfChanged(ctx, rt, pstResource, statusCondition)
+
+			return err
+		}
+
+		// Step 2: Translate it into pbproxystate.Endpoints.
+		psEndpoints, err := generateProxyStateEndpoints(serviceEndpoints, endpointRef.Port)
+		if err != nil {
+			rt.Logger.Error("error translating service endpoints to proxy state endpoints", "endpoint", endpointRef.Id, "error", err)
+
+			// Set the status.
+			statusCondition = status.ConditionRejectedCreatingProxyStateEndpoints(status.KeyFromID(endpointRef.Id), err.Error())
+			status.WriteStatusIfChanged(ctx, rt, pstResource, statusCondition)
+
+			return err
+		}
+
+		// Step 3: Add the endpoints to ProxyState.
+		proxyStateTemplate.Template.ProxyState.Endpoints[xdsClusterName] = psEndpoints
+
+		// Track all the endpoints that are used by this ProxyStateTemplate, so we can use this for step 4.
+		endpointResourceRef := resource.Reference(endpointRef.Id, "")
+		endpointsInProxyStateTemplate = append(endpointsInProxyStateTemplate, endpointResourceRef)
+
+	}
+
+	// Step 4: Track relationships between ProxyStateTemplates and ServiceEndpoints.
+	r.bimapper.TrackItem(req.ID, endpointsInProxyStateTemplate)
+
+	computedProxyState := proxyStateTemplate.Template.ProxyState
+
+	err = r.updater.PushChange(req.ID, computedProxyState)
+	if err != nil {
+		// Set the status.
+		statusCondition = status.ConditionRejectedPushChangeFailed(status.KeyFromID(req.ID))
+		status.WriteStatusIfChanged(ctx, rt, pstResource, statusCondition)
+		return err
+	}
+
+	// Set the status.
+	statusCondition = status.ConditionAccepted()
+	status.WriteStatusIfChanged(ctx, rt, pstResource, statusCondition)
+	return nil
+}
+
+func resourceIdToReference(id *pbresource.ID) *pbresource.Reference {
+	ref := &pbresource.Reference{
+		Name:    id.GetName(),
+		Type:    id.GetType(),
+		Tenancy: id.GetTenancy(),
+	}
+	return ref
+}