Exporting Metrics

By design, Linkerd only keeps metrics data for a short, fixed window of time (currently, 6 hours). This means that if Linkerd’s metrics data is valuable to you, you will probably want to export it into a full-fledged metrics store.

Internally, Linkerd stores its metrics in a Prometheus instance that runs as part of the control plane. There are several basic approaches to exporting metrics data from Linkerd:

Using the Prometheus federation API

If you are 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 Linkerd 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 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:
      linkerd.io/control-plane-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://linkerd-prometheus.linkerd.svc.cluster.local:9090/federate

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

curl http://linkerd-prometheus.linkerd.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