feat(ta): allowNamespaces and denyNamespaces

When the target allocator is configured to watch Prometheus custom
resources in the cluster to discover targets, it is currently hard-coded
to require a ClusterRole with a policy rule of listing namespaces. This
prevents usage in environments where configuring ClusterRoles is not
permitted i.e. in namespace-as-a-service setups where only Roles can be
created.

This change introduces two fields in the prometheusCR specification to
allow configuring the namespaces that can be interacted with by the
target allocator.

- allowNamespaces is a comma-separated list of namespaces for the target
  allocator to watch. If set to an empty string, it will list all
  list all namespaces in the cluster. This is mutually exclusive with
  denyNamespaces. Defaults to an empty string.
- denyNamespaces is a comma-separated list of namespaces for the target
  allocator to not watch. If set to an empty string, it will not exclude
  any namespaces. This is mutually exclusive with allowNamespaces.
  Defaults to an empty string.

Fixes: #3086

Signed-off-by: Charlie Le <[email protected]>

Author: CharlieTLe

.chloggen/namespace-ta.yaml

@@ -0,0 +1,19 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. collector, target allocator, auto-instrumentation, opamp, github action)
+component: target allocator
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: |
+  Add support for setting the allowNamespaces and denyNamespaces in the target allocator.
+
+# One or more tracking issues related to the change
+issues: [3086]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  allowNamespaces can be set to an empty string to watch all namespaces (default) or to a comma-separated list of namespaces to watch.
+  denyNamespaces can be set to an empty string to deny watching any namespaces (default) or to a comma-separated list of namespaces to deny watching.

apis/v1beta1/targetallocator_types.go

@@ -12,6 +12,12 @@ type TargetAllocatorPrometheusCR struct {
 	// Enabled indicates whether to use a PrometheusOperator custom resources as targets or not.
 	// +optional
 	Enabled bool `json:"enabled,omitempty"`
+	// AllowNamespaces Namespaces to scope the interaction of the Target Allocator and the apiserver (allow list). This is mutually exclusive with DenyNamespaces.
+	// +optional
+	AllowNamespaces string `json:"allowNamespaces,omitempty"`
+	// DenyNamespaces Namespaces to scope the interaction of the Target Allocator and the apiserver (allow list). This is mutually exclusive with AllowNamespaces.
+	// +optional
+	DenyNamespaces string `json:"denyNamespaces,omitempty"`
 	// Default interval between consecutive scrapes. Intervals set in ServiceMonitors and PodMonitors override it.
 	//Equivalent to the same setting on the Prometheus CR.
 	//

bundle/community/manifests/opentelemetry.io_opentelemetrycollectors.yaml

@@ -7889,6 +7889,10 @@ spec:
                     type: object
                   prometheusCR:
                     properties:
+                      allowNamespaces:
+                        type: string
+                      denyNamespaces:
+                        type: string
                       enabled:
                         type: boolean
                       podMonitorSelector:

bundle/community/manifests/opentelemetry.io_targetallocators.yaml

@@ -2257,6 +2257,10 @@ spec:
                 type: string
               prometheusCR:
                 properties:
+                  allowNamespaces:
+                    type: string
+                  denyNamespaces:
+                    type: string
                   enabled:
                     type: boolean
                   podMonitorSelector:

bundle/openshift/manifests/opentelemetry.io_opentelemetrycollectors.yaml

@@ -7889,6 +7889,10 @@ spec:
                     type: object
                   prometheusCR:
                     properties:
+                      allowNamespaces:
+                        type: string
+                      denyNamespaces:
+                        type: string
                       enabled:
                         type: boolean
                       podMonitorSelector:

bundle/openshift/manifests/opentelemetry.io_targetallocators.yaml

@@ -2257,6 +2257,10 @@ spec:
                 type: string
               prometheusCR:
                 properties:
+                  allowNamespaces:
+                    type: string
+                  denyNamespaces:
+                    type: string
                   enabled:
                     type: boolean
                   podMonitorSelector:

cmd/otel-allocator/README.md

@@ -191,9 +191,11 @@ Upstream documentation here: [PrometheusReceiver](https://github.com/open-teleme
 
 ### RBAC
 
-Before the TargetAllocator can start scraping, you need to set up Kubernetes RBAC (role-based access controls) resources. This means that you need to have a `ServiceAccount` and corresponding cluster roles so that the TargetAllocator has access to all of the necessary resources to pull metrics from.
+Before the TargetAllocator can start scraping, you need to set up Kubernetes RBAC (role-based access controls) resources. This means that you need to have a `ServiceAccount` and corresponding ClusterRoles/Roles so that the TargetAllocator has access to all the necessary resources to pull metrics from.
 
-You can create your own `ServiceAccount`, and reference it in `spec.targetAllocator.serviceAccount` in your `OpenTelemetryCollector` CR. You’ll then need to configure the `ClusterRole` and `ClusterRoleBinding` for this `ServiceAccount`, as per below.
+You can create your own `ServiceAccount`, and reference it in `spec.targetAllocator.serviceAccount` in your `OpenTelemetryCollector` CR. You’ll then need to configure the `ClusterRole` and `ClusterRoleBinding` or `Role` and `RoleBinding` for this `ServiceAccount`, as per below.
+
+#### Cluster-scoped RBAC
 
 ```yaml
   targetAllocator:
@@ -204,11 +206,11 @@ You can create your own `ServiceAccount`, and reference it in `spec.targetAlloca
 ```
 
 > 🚨 **Note**: The Collector part of this same CR *also* has a serviceAccount key which only affects the collector and *not*
-the TargetAllocator.
+> the TargetAllocator.
 
-If you omit the `ServiceAccount` name, the TargetAllocator creates a `ServiceAccount` for you. The `ServiceAccount`’s default name is a concatenation of the Collector name and the `-targetallocator` suffix. By default, this `ServiceAccount` has no defined policy, so you’ll need to create your own `ClusterRole` and `ClusterRoleBinding` for it, as per below.
+If you omit the `ServiceAccount` name, the TargetAllocator creates a `ServiceAccount` for you. The `ServiceAccount`’s default name is a concatenation of the Collector name and the `-targetallocator` suffix. By default, this `ServiceAccount` has no defined policy, so you’ll need to create your own `ClusterRole` and `ClusterRoleBinding` or `Role` and `RoleBinding` for it, as per below.
 
-The role below will provide the minimum access required for the Target Allocator to query all the targets it needs based on any Prometheus configurations:
+The ClusterRole below will provide the minimum access required for the Target Allocator to query all the targets it needs based on any Prometheus configurations:
 
 ```yaml
 apiVersion: rbac.authorization.k8s.io/v1
@@ -242,7 +244,7 @@ rules:
   verbs: ["get"]
 ```
 
-If you enable the the `prometheusCR` (set `spec.targetAllocator.prometheusCR.enabled` to `true`) in the `OpenTelemetryCollector` CR, you will also need to define the following roles. These give the TargetAllocator access to the `PodMonitor` and `ServiceMonitor` CRs. It also gives namespace access to the `PodMonitor` and `ServiceMonitor`.
+If you enable the `prometheusCR` (set `spec.targetAllocator.prometheusCR.enabled` to `true`) in the `OpenTelemetryCollector` CR, you will also need to define the following ClusterRoles. These give the TargetAllocator access to the `PodMonitor` and `ServiceMonitor` CRs. It also gives namespace access to the `PodMonitor` and `ServiceMonitor`.
 
 ```yaml
 apiVersion: rbac.authorization.k8s.io/v1
@@ -263,8 +265,81 @@ rules:
   verbs: ["get", "list", "watch"]
 ```
 
-> ✨ The above roles can be combined into a single role.
+> ✨ The above ClusterRoles can be combined into a single ClusterRole.
+ 
+#### Namespace-scoped RBAC
+
+If you want to have the TargetAllocator watch a specific namespace, you can set the allowNamespaces field 
+in the TargetAllocator's prometheusCR configuration. This is useful if you want to restrict the TargetAllocator to only watch Prometheus
+CRs in a specific namespace, and not have cluster-wide access.
+
+```yaml
+  targetAllocator:
+    enabled: true
+    serviceAccount: opentelemetry-targetallocator-sa
+    prometheusCR:
+      enabled: true
+      allowNamespaces: foo
+```
+
+In this case, you will need to create a Role and RoleBinding instead of a ClusterRole and ClusterRoleBinding. The Role
+and RoleBinding should be created in the namespace specified by the allowNamespaces field.
 
+```yaml
+apiVersion: rbac.authorization.k8s.io/v1
+kind: Role
+metadata:
+  name: opentelemetry-targetallocator-role
+rules:
+  - apiGroups:
+      - ""
+    resources:
+      - pods
+      - services
+      - endpoints
+      - configmaps
+      - secrets
+      - namespaces
+    verbs:
+      - get
+      - watch
+      - list
+  - apiGroups:
+      - apps
+    resources:
+      - statefulsets
+    verbs:
+      - get
+      - watch
+      - list
+  - apiGroups:
+      - discovery.k8s.io
+    resources:
+      - endpointslices
+    verbs:
+      - get
+      - watch
+      - list
+  - apiGroups:
+      - networking.k8s.io
+    resources:
+      - ingresses
+    verbs:
+      - get
+      - watch
+      - list
+  - apiGroups:
+      - monitoring.coreos.com
+    resources:
+      - servicemonitors
+      - podmonitors
+      - scrapeconfigs
+      - probes
+    verbs:
+      - get
+      - watch
+      - list
+```
 
 ### Service / Pod monitor endpoint credentials
 
@@ -420,4 +495,3 @@ Shards the received targets based on the discovered Collector instances
 
 ### Collector
 Client to watch for deployed Collector instances which will then provided to the Allocator. 
-

cmd/otel-allocator/internal/config/config.go

@@ -53,6 +53,8 @@ type Config struct {
 
 type PrometheusCRConfig struct {
 	Enabled                         bool                  `yaml:"enabled,omitempty"`
+	AllowNamespaces                 string                `yaml:"allow_namespaces,omitempty"`
+	DenyNamespaces                  string                `yaml:"deny_namespaces,omitempty"`
 	PodMonitorSelector              *metav1.LabelSelector `yaml:"pod_monitor_selector,omitempty"`
 	PodMonitorNamespaceSelector     *metav1.LabelSelector `yaml:"pod_monitor_namespace_selector,omitempty"`
 	ServiceMonitorSelector          *metav1.LabelSelector `yaml:"service_monitor_selector,omitempty"`

cmd/otel-allocator/internal/watcher/promOperator.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"log/slog"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/blang/semver/v4"
@@ -53,7 +54,30 @@ func NewPrometheusCRWatcher(ctx context.Context, logger logr.Logger, cfg allocat
 		return nil, err
 	}
 
-	factory := informers.NewMonitoringInformerFactories(map[string]struct{}{v1.NamespaceAll: {}}, map[string]struct{}{}, mClient, allocatorconfig.DefaultResyncTime, nil) //TODO decide what strategy to use regarding namespaces
+	if cfg.PrometheusCR.AllowNamespaces != "" && cfg.PrometheusCR.DenyNamespaces != "" {
+		return nil, fmt.Errorf("both allow and deny namespaces are set, only one should be set")
+	}
+
+	allowList := map[string]struct{}{}
+	if cfg.PrometheusCR.AllowNamespaces != "" {
+		logger.Info("watching namespace(s)", "namespaces", cfg.PrometheusCR.AllowNamespaces)
+		for _, ns := range strings.Split(cfg.PrometheusCR.AllowNamespaces, ",") {
+			allowList[ns] = struct{}{}
+		}
+	} else {
+		logger.Info("cfg.PrometheusCR.AllowNamespaces is unset, watching all namespaces")
+		allowList = map[string]struct{}{v1.NamespaceAll: {}}
+	}
+
+	denyList := map[string]struct{}{}
+	if cfg.PrometheusCR.DenyNamespaces != "" {
+		logger.Info("excluding namespace(s)", "namespaces", cfg.PrometheusCR.DenyNamespaces)
+		for _, ns := range strings.Split(cfg.PrometheusCR.DenyNamespaces, ",") {
+			denyList[ns] = struct{}{}
+		}
+	}
+
+	factory := informers.NewMonitoringInformerFactories(allowList, denyList, mClient, allocatorconfig.DefaultResyncTime, nil)
 
 	monitoringInformers, err := getInformers(factory)
 	if err != nil {
@@ -99,7 +123,7 @@ func NewPrometheusCRWatcher(ctx context.Context, logger logr.Logger, cfg allocat
 			logger.Error(err, "Retrying namespace informer creation in promOperator CRD watcher")
 			return true
 		}, func() error {
-			nsMonInf, err = getNamespaceInformer(ctx, map[string]struct{}{v1.NamespaceAll: {}}, promLogger, clientset, operatorMetrics)
+			nsMonInf, err = getNamespaceInformer(ctx, allowList, denyList, promLogger, clientset, operatorMetrics)
 			return err
 		})
 	if getNamespaceInformerErr != nil {
@@ -149,7 +173,7 @@ type PrometheusCRWatcher struct {
 	store                           *assets.StoreBuilder
 }
 
-func getNamespaceInformer(ctx context.Context, allowList map[string]struct{}, promOperatorLogger *slog.Logger, clientset kubernetes.Interface, operatorMetrics *operator.Metrics) (cache.SharedIndexInformer, error) {
+func getNamespaceInformer(ctx context.Context, allowList, denyList map[string]struct{}, promOperatorLogger *slog.Logger, clientset kubernetes.Interface, operatorMetrics *operator.Metrics) (cache.SharedIndexInformer, error) {
 	kubernetesVersion, err := clientset.Discovery().ServerVersion()
 	if err != nil {
 		return nil, err
@@ -165,7 +189,7 @@ func getNamespaceInformer(ctx context.Context, allowList map[string]struct{}, pr
 		clientset.CoreV1(),
 		clientset.AuthorizationV1().SelfSubjectAccessReviews(),
 		allowList,
-		map[string]struct{}{},
+		denyList,
 	)
 	if err != nil {
 		return nil, err

config/crd/bases/opentelemetry.io_opentelemetrycollectors.yaml

@@ -7875,6 +7875,10 @@ spec:
                     type: object
                   prometheusCR:
                     properties:
+                      allowNamespaces:
+                        type: string
+                      denyNamespaces:
+                        type: string
                       enabled:
                         type: boolean
                       podMonitorSelector:

config/crd/bases/opentelemetry.io_targetallocators.yaml

@@ -2254,6 +2254,10 @@ spec:
                 type: string
               prometheusCR:
                 properties:
+                  allowNamespaces:
+                    type: string
+                  denyNamespaces:
+                    type: string
                   enabled:
                     type: boolean
                   podMonitorSelector: