Selectors and Scrape Configs

The Monitoring app sets prometheus.prometheusSpec.ignoreNamespaceSelectors=false, which enables monitoring across all namespaces by default.

This ensures you can view traffic, metrics and graphs for resources deployed in a namespace with istio-injection=enabled label.

If you would like to limit Prometheus to specific namespaces, set prometheus.prometheusSpec.ignoreNamespaceSelectors=true. Once you do this, you must perform some additional configuration to continue to monitor your resources.

Limiting Monitoring to Specific Namespaces by Setting ignoreNamespaceSelectors to True

To limit monitoring to specific namespaces, you will edit the ignoreNamespaceSelectors Helm chart option. You will configure this option when installing or upgrading the Monitoring Helm chart:

When installing or upgrading the Monitoring Helm chart, edit the values.yml and setprometheus.prometheusSpec.ignoreNamespaceSelectors=true.
Complete the install or upgrade.

Result: Prometheus will be limited to specific namespaces which means one of the following configurations will need to be set up to continue to view data in various dashboards

Enabling Prometheus to Detect Resources in Other Namespaces

There are two different ways to enable Prometheus to detect resources in other namespaces when prometheus.prometheusSpec.ignoreNamespaceSelectors=true:

Monitoring specific namespaces: Add a Service Monitor or Pod Monitor in the namespace with the targets you want to scrape.
Monitoring across namespaces: Add an additionalScrapeConfig to your rancher-monitoring instance to scrape all targets in all namespaces.

Monitoring Specific Namespaces: Create a Service Monitor or Pod Monitor

This option allows you to define which specific services or pods you would like monitored in a specific namespace.

The usability tradeoff is that you have to create the service monitor or pod monitor per namespace since you cannot monitor across namespaces.

Prerequisite:

Define a ServiceMonitor or PodMonitor for <your namespace>. An example ServiceMonitor is provided below.

Click ☰ > Cluster Management.
Go to the cluster that you created and click Explore.
In the top navigation bar, open the kubectl shell.
If the ServiceMonitor or PodMonitor file is stored locally in your cluster, in kubectl create -f <name of service/pod monitor file>.yaml.
If the ServiceMonitor or PodMonitor is not stored locally, run cat<< EOF | kubectl apply -f -, paste the file contents into the terminal, then run EOF to complete the command.
Run kubectl label namespace <your namespace> istio-injection=enabled to enable the envoy sidecar injection.

Result: <your namespace> can be scraped by prometheus.

Example Service Monitor for Istio Proxies

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: envoy-stats-monitor
  namespace: istio-system
  labels:
    monitoring: istio-proxies
spec:
  selector:
    matchExpressions:
    - {key: istio-prometheus-ignore, operator: DoesNotExist}
  namespaceSelector:
    any: true
  jobLabel: envoy-stats
  endpoints:
  - path: /stats/prometheus
    targetPort: 15090
    interval: 15s
    relabelings:
    - sourceLabels: [__meta_kubernetes_pod_container_port_name]
      action: keep
      regex: '.*-envoy-prom'
    - action: labeldrop
      regex: "__meta_kubernetes_pod_label_(.+)"
    - sourceLabels: [__meta_kubernetes_namespace]
      action: replace
      targetLabel: namespace
    - sourceLabels: [__meta_kubernetes_pod_name]
      action: replace
      targetLabel: pod_name

Monitoring across namespaces: Set ignoreNamespaceSelectors to False

This enables monitoring across namespaces by giving Prometheus additional scrape configurations.

The usability tradeoff is that all of Prometheus' additionalScrapeConfigs are maintained in a single Secret. This could make upgrading difficult if monitoring is already deployed with additionalScrapeConfigs before installing Istio.

When installing or upgrading the Monitoring Helm chart, edit the values.yml and set the prometheus.prometheusSpec.additionalScrapeConfigs array to the Additional Scrape Config provided below.
Complete the install or upgrade.

Result: All namespaces with the istio-injection=enabled label will be scraped by prometheus.

Additional Scrape Config

- job_name: 'istio/envoy-stats'
  scrape_interval: 15s
  metrics_path: /stats/prometheus
  kubernetes_sd_configs:
    - role: pod
  relabel_configs:
    - source_labels: [__meta_kubernetes_pod_container_port_name]
      action: keep
      regex: '.*-envoy-prom'
    - source_labels: [__address__, __meta_kubernetes_pod_annotation_prometheus_io_port]
      action: replace
      regex: ([^:]+)(?::\d+)?;(\d+)
      replacement: $1:15090
      target_label: __address__
    - action: labelmap
      regex: __meta_kubernetes_pod_label_(.+)
    - source_labels: [__meta_kubernetes_namespace]
      action: replace
      target_label: namespace
    - source_labels: [__meta_kubernetes_pod_name]
      action: replace
      target_label: pod_name