Exporting Metrics

Linkerd provides an extensive set of metrics for all traffic that passes through its data plane. These metrics are collected at the proxy level and reported on the proxy’s metrics endpoint.

Typically, consuming these metrics is not done from the proxies directly, as each proxy only provides a portion of the full picture. Instead, a separate tool is used to collect metrics from all proxies and aggregate them together for consumption.

One easy option is the linkerd-viz extension, which will create an on-cluster Prometheus instance as well as dashboards and CLI commands that make use of it. However, this extension only keeps metrics data for a brief window of time (6 hours) and does not persist data across restarts. Depending on your use case, you may want to export these metrics into an external metrics store.

There are several options for how to export these metrics to a destination outside of the cluster:

• Federate data from linkerd-viz to your own Prometheus cluster
• Use a Prometheus integration with linkerd-viz
• Extract data from linkerd-viz via Prometheus’s APIs
• Gather data from the proxies directly without linkerd-viz

Using the Prometheus federation API

If you are already using Prometheus as your own metrics store, we recommend taking advantage of Prometheus’s federation API, which is designed exactly for the use case of copying data from one Prometheus to another.

Simply add the following item to your scrape_configs in your Prometheus config file (replace {{.Namespace}} with the namespace where the Linkerd Viz extension is running):

- job_name: 'linkerd'
  kubernetes_sd_configs:
  - role: pod
    namespaces:
      names: ['{{.Namespace}}']

  relabel_configs:
  - source_labels:
    - __meta_kubernetes_pod_container_name
    action: keep
    regex: ^prometheus$

  honor_labels: true
  metrics_path: '/federate'

  params:
    'match[]':
      - '{job="linkerd-proxy"}'
      - '{job="linkerd-controller"}'

Alternatively, if you prefer to use Prometheus’ ServiceMonitors to configure your Prometheus, you can use this ServiceMonitor YAML (replace {{.Namespace}} with the namespace where Linkerd Viz extension is running):

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  labels:
    k8s-app: linkerd-prometheus
    release: monitoring
  name: linkerd-federate
  namespace: {{.Namespace}}
spec:
  endpoints:
  - interval: 30s
    scrapeTimeout: 30s
    params:
      match[]:
      - '{job="linkerd-proxy"}'
      - '{job="linkerd-controller"}'
    path: /federate
    port: admin-http
    honorLabels: true
    relabelings:
    - action: keep
      regex: '^prometheus$'
      sourceLabels:
      - '__meta_kubernetes_pod_container_name'
  jobLabel: app
  namespaceSelector:
    matchNames:
    - {{.Namespace}}
  selector:
    matchLabels:
      component: prometheus

That’s it! Your Prometheus cluster is now configured to federate Linkerd’s metrics from Linkerd’s internal Prometheus instance.

Once the metrics are in your Prometheus, Linkerd’s proxy metrics will have the label job="linkerd-proxy" and Linkerd’s control plane metrics will have the label job="linkerd-controller". For more information on specific metric and label definitions, have a look at Proxy Metrics.

For more information on Prometheus’ /federate endpoint, have a look at the Prometheus federation docs.

Using a Prometheus integration

If you are not using Prometheus as your own long-term data store, you may be able to leverage one of Prometheus’s many integrations to automatically extract data from Linkerd’s Prometheus instance into the data store of your choice. Please refer to the Prometheus documentation for details.

Extracting data via Prometheus’s APIs

If neither Prometheus federation nor Prometheus integrations are options for you, it is possible to call Prometheus’s APIs to extract data from Linkerd.

For example, you can call the federation API directly via a command like:

curl -G \
  --data-urlencode 'match[]={job="linkerd-proxy"}' \
  --data-urlencode 'match[]={job="linkerd-controller"}' \
  http://prometheus.linkerd-viz.svc.cluster.local:9090/federate

Similar to the /federate API, Prometheus provides a JSON query API to retrieve all metrics:

curl http://prometheus.linkerd-viz.svc.cluster.local:9090/api/v1/query?query=request_total

Gathering data from the Linkerd proxies directly

Finally, if you want to avoid Linkerd’s Prometheus entirely, you can query the Linkerd proxies directly on their /metrics endpoint.

For example, to view /metrics from a single Linkerd proxy, running in the linkerd namespace:

kubectl -n linkerd port-forward \
  $(kubectl -n linkerd get pods \
    -l linkerd.io/control-plane-ns=linkerd \
    -o jsonpath='{.items[0].metadata.name}') \
  4191:4191

and then:

curl localhost:4191/metrics

Alternatively, linkerd diagnostics proxy-metrics can be used to retrieve proxy metrics for a given workload.