Thanos

Thanos and the Prometheus Operator.

Thanos is a set of components that can be composed into a highly available, multi Prometheus metric system with potentially unlimited storage capacity, if your Object Storage allows for it.

Before continuing with Prometheus Operator Thanos integration, it is recommended to read more about Thanos in the official documentation.

What does the Prometheus Operator help with?

Prometheus Operator can manage:

  • the Thanos sidecar component with the Prometheus custom resource definition. Deployed within the Prometheus pod, it can hook into the Thanos querying system as well as optionally back up your data to object storage.
  • Thanos Ruler instances with the ThanosRuler custom resource definition.

Other Thanos components such the Querier, the Receiver, the Compactor and the Store Gateway should be deployed independently of the Prometheus Operator and its Thanos configuration. The kube-thanos project has some starting points for other Thanos components deployments.

Prometheus Custom Resource with Thanos Sidecar

The Prometheus CRD has support for adding a Thanos sidecar to the Prometheus Pod. To enable the sidecar, the thanos section must be set to a non empty value. For example, the simplest configuration is to just set a valid thanos container image url.

...
spec:
  ...
  thanos:
    image: quay.io/thanos/thanos:v0.28.1
...

Configuring Thanos Object Storage

You can configure the Thanos sidecar to upload TSDB blocks to object storage by providing a Kubernetes Secret containing the required configuration.

For more information and examples about the configuration itself, take a look at the Thanos documentation.

Once you have written your configuration save it to a file. Here’s an example:

type: s3
config:
  bucket: thanos
  endpoint: ams3.digitaloceanspaces.com
  access_key: XXX
  secret_key: XXX

Let’s assume you saved this file to /tmp/thanos-config.yaml. You can use the following command to create a secret called thanos-objstore-config inside your cluster in the monitoring namespace.

kubectl -n monitoring create secret generic thanos-objstore-config --from-file=thanos.yaml=/tmp/thanos-config.yaml

Then you can specify this secret inside the Thanos field of the Prometheus spec as mentioned earlier:

...
spec:
  ...
  thanos:
    image: quay.io/thanos/thanos:v0.28.1
    objectStorageConfig:
      key: thanos.yaml
      name: thanos-objstore-config
...

This will attach Thanos sidecar that will backup all new blocks that Prometheus produces every 2 hours to the object storage.

NOTE: This option will also disable the local Prometheus compaction. This means that Thanos compactor is the main singleton component responsible for compactions on a global, object storage level.

Thanos Ruler

The Thanos Ruler component evaluates Prometheus recording and alerting rules against chosen query API. A ThanosRuler instance requires at least one Query API server defined either by the .spec.queryConfig field or the .spec.queryEndpoints field. It can also be configured to send alerts to Alertmanager with the .spec.alertmanagersConfig.

...
apiVersion: monitoring.coreos.com/v1
kind: ThanosRuler
metadata:
  name: thanos-ruler-demo
  labels:
    example: thanos-ruler
  namespace: monitoring
spec:
  image: quay.io/thanos/thanos:v0.28.1
  ruleSelector:
    matchLabels:
      role: my-thanos-rules
  queryEndpoints:
    - dnssrv+_http._tcp.my-thanos-querier.monitoring.svc.cluster.local
  alertmanagersConfig:
    key: alertmanager-configs.yaml
    name: thanosruler-alertmanager-config

More context for your Alertmanager configuration can be found in the Thanos documentation. An example:

apiVersion: v1
kind: Secret
metadata:
  name: thanosruler-alertmanager-config
stringData:
  alertmanager-configs.yaml: |-
    alertmanagers:
    - static_configs:
      - "dnssrv+_web._tcp.alertmanager-operated.monitoring.svc.cluster.local"
      api_version: v2

Can be saved as /tmp/alertmanager-configs.yaml, and you can create in your namespace, for example monitoring as thanosruler-alertmanager-config imperatively with:

kubectl -n monitoring create secret generic thanosruler-alertmanager-config --from-file=alertmanager-configs.yaml=/tmp/alertmanager-configs.yaml

The recording and alerting rules used by a ThanosRuler component, are configured using the same PrometheusRule objects which are used by Prometheus. In the given example, the rules contained in any PrometheusRule object which match the label role=my-thanos-rules will be loaded by the Thanos Ruler pods.

Other Thanos Components

Deploying the sidecar was the first step towards getting Thanos up and running, but there are more components to be deployed to get a complete Thanos setup.

Additionally, when object storage backup is desired:

kube-thanos project has already supported several thanos components. For more details, please checkout kube-thanos.

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