Configure Prometheus to scrape Kubelets directly

* Use Kubelet bearer token authn/authz to scrape metrics
* Drop RBAC permission from nodes/proxy to nodes/metrics
* Stop proxying kubelet scrapes through the apiserver, since
this required higher privilege (nodes/proxy) and can add
load to the apiserver on large clusters

CHANGES.md

@@ -6,7 +6,7 @@ Notable changes between versions.
 
 * Update etcd from v3.3.4 to v3.3.5 ([#213](https://github.com/poseidon/typhoon/pull/213))
 * Require Terraform v0.11.x and drop support for v0.10.x ([migration guide](https://typhoon.psdn.io/topics/maintenance/#terraform-v011x))
-* Allow bearer token authentication to the Kubelet ([#216](https://github.com/poseidon/typhoon/issues/215))
+* Allow bearer token authentication to the Kubelet ([#216](https://github.com/poseidon/typhoon/issues/216))
   * Require Webhook authorization to the Kubelet
   * Switch apiserver X509 client cert org to satisfy new authorization requirement
 
@@ -22,6 +22,9 @@ Notable changes between versions.
 #### Addons
 
 * Fix Prometheus data directory location ([#203](https://github.com/poseidon/typhoon/pull/203))
+* Configure Prometheus to scrape Kubelets directly with bearer token auth instead of proxying through the apiserver ([#217](https://github.com/poseidon/typhoon/pull/217))
+  * Security improvement: Drop RBAC permission from `nodes/proxy` to `nodes/metrics`
+  * Scale: Remove per-node proxied scrape load from the apiserver
 * Update Grafana from v5.04 to v5.1.2 ([#208](https://github.com/poseidon/typhoon/pull/208))
   * Disable Grafana Google Analytics by default ([#214](https://github.com/poseidon/typhoon/issues/214))
 

addons/prometheus/config.yaml

@@ -56,12 +56,7 @@ data:
         target_label: job
 
     # Scrape config for node (i.e. kubelet) /metrics (e.g. 'kubelet_'). Explore
-    # metrics from a node by scraping kubelet (127.0.0.1:10255/metrics).
+    # metrics from a node by scraping kubelet (127.0.0.1:10250/metrics).
-    #
-    # Rather than connecting directly to the node, the scrape is proxied though the
-    # Kubernetes apiserver.  This means it will work if Prometheus is running out of
-    # cluster, or can't connect to nodes for some other reason (e.g. because of
-    # firewalling).
     - job_name: 'kubelet'
       kubernetes_sd_configs:
       - role: node
@@ -69,50 +64,34 @@ data:
       scheme: https
       tls_config:
         ca_file: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
+        # Kubelet certs don't have any fixed IP SANs
+        insecure_skip_verify: true
       bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
 
       relabel_configs:
       - action: labelmap
         regex: __meta_kubernetes_node_label_(.+)
-      - target_label: __address__
-        replacement: kubernetes.default.svc:443
-      - source_labels: [__meta_kubernetes_node_name]
-        regex: (.+)
-        target_label: __metrics_path__
-        replacement: /api/v1/nodes/${1}/proxy/metrics
 
     # Scrape config for Kubelet cAdvisor. Explore metrics from a node by
-    # scraping kubelet (127.0.0.1:10255/metrics/cadvisor).
+    # scraping kubelet (127.0.0.1:10250/metrics/cadvisor).
-    #
-    # This is required for Kubernetes 1.7.3 and later, where cAdvisor metrics
-    # (those whose names begin with 'container_') have been removed from the
-    # Kubelet metrics endpoint.  This job scrapes the cAdvisor endpoint to
-    # retrieve those metrics.
-    #
-    # Rather than connecting directly to the node, the scrape is proxied though the
-    # Kubernetes apiserver.  This means it will work if Prometheus is running out of
-    # cluster, or can't connect to nodes for some other reason (e.g. because of
-    # firewalling).
     - job_name: 'kubernetes-cadvisor'
       kubernetes_sd_configs:
       - role: node
 
       scheme: https
+      metrics_path: /metrics/cadvisor
       tls_config:
+        # Kubelet certs don't have any fixed IP SANs
+        insecure_skip_verify: true
         ca_file: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
       bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
 
       relabel_configs:
       - action: labelmap
         regex: __meta_kubernetes_node_label_(.+)
-      - target_label: __address__
-        replacement: kubernetes.default.svc:443
-      - source_labels: [__meta_kubernetes_node_name]
-        regex: (.+)
-        target_label: __metrics_path__
-        replacement: /api/v1/nodes/${1}/proxy/metrics/cadvisor
 
-    # Scrap etcd metrics from controllers 
+
+    # Scrap etcd metrics from controllers via listen-metrics-urls
     - job_name: 'etcd'
       kubernetes_sd_configs:
       - role: node

addons/prometheus/rbac/cluster-role.yaml

@@ -6,7 +6,7 @@ rules:
 - apiGroups: [""]
   resources:
   - nodes
-  - nodes/proxy
+  - nodes/metrics
   - services
   - endpoints
   - pods

aws/container-linux/kubernetes/security.tf

@@ -91,6 +91,16 @@ resource "aws_security_group_rule" "controller-node-exporter" {
   source_security_group_id = "${aws_security_group.worker.id}"
 }
 
+resource "aws_security_group_rule" "controller-kubelet" {
+  security_group_id = "${aws_security_group.controller.id}"
+
+  type      = "ingress"
+  protocol  = "tcp"
+  from_port = 10250
+  to_port   = 10250
+  source_security_group_id = "${aws_security_group.worker.id}"
+}
+
 resource "aws_security_group_rule" "controller-kubelet-self" {
   security_group_id = "${aws_security_group.controller.id}"
 

aws/fedora-atomic/kubernetes/security.tf

@@ -91,6 +91,16 @@ resource "aws_security_group_rule" "controller-node-exporter" {
   source_security_group_id = "${aws_security_group.worker.id}"
 }
 
+resource "aws_security_group_rule" "controller-kubelet" {
+  security_group_id = "${aws_security_group.controller.id}"
+
+  type      = "ingress"
+  protocol  = "tcp"
+  from_port = 10250
+  to_port   = 10250
+  source_security_group_id = "${aws_security_group.worker.id}"
+}
+
 resource "aws_security_group_rule" "controller-kubelet-self" {
   security_group_id = "${aws_security_group.controller.id}"
 

google-cloud/container-linux/kubernetes/network.tf

@@ -121,7 +121,7 @@ resource "google_compute_firewall" "internal-node-exporter" {
   target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }
 
-# kubelet API to allow kubectl exec and log
+# kubelet API to allow apiserver exec and log or metrics scraping
 resource "google_compute_firewall" "internal-kubelet" {
   name    = "${var.cluster_name}-internal-kubelet"
   network = "${google_compute_network.network.name}"
@@ -131,7 +131,7 @@ resource "google_compute_firewall" "internal-kubelet" {
     ports    = [10250]
   }
 
-  source_tags = ["${var.cluster_name}-controller"]
+  source_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
   target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }
 

google-cloud/fedora-atomic/kubernetes/network.tf

@@ -121,7 +121,7 @@ resource "google_compute_firewall" "internal-node-exporter" {
   target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }
 
-# kubelet API to allow kubectl exec and log
+# kubelet API to allow apiserver exec and log or metrics scraping
 resource "google_compute_firewall" "internal-kubelet" {
   name    = "${var.cluster_name}-internal-kubelet"
   network = "${google_compute_network.network.name}"
@@ -131,7 +131,7 @@ resource "google_compute_firewall" "internal-kubelet" {
     ports    = [10250]
   }
 
-  source_tags = ["${var.cluster_name}-controller"]
+  source_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
   target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }