Guide on troubleshooting the Prometheus Operator.
2021-03-08 08:49:31 +0000
RBAC on Google Container Engine (GKE)
When you try to create
prometheus-operator, etc.) on GKE Kubernetes cluster running 1.6 version, you will probably run into permission errors:
<....> Error from server (Forbidden): error when creating "manifests/prometheus-operator/prometheus-operator-cluster-role.yaml": clusterroles.rbac.authorization.k8s.io "prometheus-operator" is forbidden: attempt to grant extra privileges: <....>
This is due to the way Container Engine checks permissions. From Google Kubernetes Engine docs:
Because of the way Container Engine checks permissions when you create a Role or ClusterRole, you must first create a RoleBinding that grants you all of the permissions included in the role you want to create. An example workaround is to create a RoleBinding that gives your Google identity a cluster-admin role before attempting to create additional Role or ClusterRole permissions. This is a known issue in the Beta release of Role-Based Access Control in Kubernetes and Container Engine version 1.6.
To overcome this, you must grant your current Google identity
# get current google identity $ gcloud info | grep Account Account: [email@example.com] # grant cluster-admin to your current identity $ kubectl create clusterrolebinding myname-cluster-admin-binding --clusterrole=cluster-admin --firstname.lastname@example.org Clusterrolebinding "myname-cluster-admin-binding" created
Troubleshooting ServiceMonitor changes
ServiceMonitor objects it is sometimes not as obvious what piece is not working properly. This section gives a step by step guide how to troubleshoot such actions on a
ServiceMonitor tagging and related elements
A common problem related to
ServiceMonitor identification by Prometheus is related to an incorrect tagging, that does not match the
Prometheus custom resource definition scope, or lack of permission for the Prometheus
ServiceAccount to get, list, watch
Endpoints from the target application being monitored. As a general guideline consider the diagram below, giving an example of a
my-app, being monitored by Prometheus based on a
ServiceMonitor references a
Service (not a
Deployment, or a
Pod), by labels and by the port name in the
Service. This port name is optional in Kubernetes, but must be specified for the
ServiceMonitor to work. It is not the same as the port name on the
Pod or container, although it can be.
ServiceMonitor been picked up by Prometheus?
ServiceMonitor objects and the namespace where they belong are selected by the
serviceMonitorNamespaceSelectorof a Prometheus object. The name of a
ServiceMonitor is encoded in the Prometheus configuration, so you can simply grep whether it is present there. The configuration generated by the Prometheus Operator is stored in a Kubernetes
Secret, named after the Prometheus object name prefixed with
prometheus- and is located in the same namespace as the Prometheus object. For example for a Prometheus object called
k8s one can find out if the
my-service-monitor has been picked up with:
kubectl -n monitoring get secret prometheus-k8s -ojson | jq -r '.data["prometheus.yaml.gz"]' | base64 -d | gunzip | grep "my-service-monitor"
Prometheus kubelet metrics server returned HTTP status 403 Forbidden
Prometheus is installed, all looks good, however the
Targets are all showing as down. All permissions seem to be good, yet no joy. Prometheus pulling metrics from all namespaces expect kube-system, and Prometheus has access to all namespaces including kube-system.
Did you check the webhooks?
Issue has been resolved by amending the webhooks to use
0.0.0.0 instead of
127.0.0.1. Follow the below commands and it will update the webhooks which allows connections to all
clusterIP's in all
namespaces and not just
Update the kubelet service to include webhook and restart:
KUBEADM_SYSTEMD_CONF=/etc/systemd/system/kubelet.service.d/10-kubeadm.conf sed -e "/cadvisor-port=0/d" -i "$KUBEADM_SYSTEMD_CONF" if ! grep -q "authentication-token-webhook=true" "$KUBEADM_SYSTEMD_CONF"; then sed -e "s/--authorization-mode=Webhook/--authentication-token-webhook=true --authorization-mode=Webhook/" -i "$KUBEADM_SYSTEMD_CONF" fi systemctl daemon-reload systemctl restart kubelet
Modify the kube controller and kube scheduler to allow for reading data:
sed -e "s/- --address=127.0.0.1/- --address=0.0.0.0/" -i /etc/kubernetes/manifests/kube-controller-manager.yaml sed -e "s/- --address=127.0.0.1/- --address=0.0.0.0/" -i /etc/kubernetes/manifests/kube-scheduler.yaml
Using textual port number instead of port name
The ServiceMonitor expects to use the port name as defined on the Service. So, using the Service example from the diagram above, we have this Service definition:
kind: Service metadata: labels: k8s-app: my-app name: my-app ... spec: ports: - name: metrics port: 8080 selector: k8s-app: my-app
We would then define the service monitor using
metrics as the port not
kind: ServiceMonitor metadata: name: my-app spec: ... endpoints: - port: metrics
kind: ServiceMonitor metadata: name: my-app spec: ... endpoints: - port: "8080"
The incorrect example will give an error along these lines
spec.endpoints.port in body must be of type string: "integer"