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  9 minute read  

Logging and Monitoring for Extensions

Gardener provides an integrated logging and monitoring stack for alerting, monitoring, and troubleshooting of its managed components by operators or end users. For further information how to make use of it in these roles, refer to the corresponding guides for exploring logs and for monitoring with Plutono.

The components that constitute the logging and monitoring stack are managed by Gardener. By default, it deploys Prometheus and Alertmanager (managed via prometheus-operator, and Plutono into the garden namespace of all seed clusters. If the logging is enabled in the gardenlet configuration (logging.enabled), it will deploy fluent-operator and Vali in the garden namespace too.

Each shoot namespace hosts managed logging and monitoring components. As part of the shoot reconciliation flow, Gardener deploys a shoot-specific Prometheus, Plutono and, if configured, an Alertmanager into the shoot namespace, next to the other control plane components. If the logging is enabled in the gardenlet configuration (logging.enabled) and the shoot purpose is not testing, it deploys a shoot-specific Vali in the shoot namespace too.

The logging and monitoring stack is extensible by configuration. Gardener extensions can take advantage of that and contribute monitoring configurations encoded in ConfigMaps for their own, specific dashboards, alerts and other supported assets and integrate with it. As with other Gardener resources, they will be continuously reconciled. The extensions can also deploy directly fluent-operator custom resources which will be created in the seed cluster and plugged into the fluent-bit instance.

This guide is about the roles and extensibility options of the logging and monitoring stack components, and how to integrate extensions with:

Monitoring

Cache Prometheus

The central Prometheus instance in the garden namespace (called “cache Prometheus”) fetches metrics and data from all seed cluster nodes and all seed cluster pods. It uses the federation concept to allow the shoot-specific instances to scrape only the metrics for the pods of the control plane they are responsible for. This mechanism allows to scrape the metrics for the nodes/pods once for the whole cluster, and to have them distributed afterwards. For more details, continue reading here.

Typically, this is not necessary, but in case an extension wants to extend the configuration for this cache Prometheus, they can create the prometheus-operator’s custom resources and label them with prometheus=cache, for example:

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  labels:
    prometheus: cache
  name: cache-my-component
  namespace: garden
spec:
  selector:
    matchLabels:
      app: my-component
  endpoints:
  - metricRelabelings:
    - action: keep
      regex: ^(metric1|metric2|...)$
      sourceLabels:
      - __name__
    port: metrics

Seed Prometheus

Another Prometheus instance in the garden namespace (called “seed Prometheus”) fetches metrics and data from seed system components, kubelets, cAdvisors, and extensions. If you want your extension pods to be scraped then they must be annotated with prometheus.io/scrape=true and prometheus.io/port=<metrics-port>. For more details, continue reading here.

Typically, this is not necessary, but in case an extension wants to extend the configuration for this seed Prometheus, they can create the prometheus-operator’s custom resources and label them with prometheus=seed, for example:

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  labels:
    prometheus: seed
  name: seed-my-component
  namespace: garden
spec:
  selector:
    matchLabels:
      app: my-component
  endpoints:
  - metricRelabelings:
    - action: keep
      regex: ^(metric1|metric2|...)$
      sourceLabels:
      - __name__
    port: metrics

Aggregate Prometheus

Another Prometheus instance in the garden namespace (called “aggregate Prometheus”) stores pre-aggregated data from the cache Prometheus and shoot Prometheis. An ingress exposes this Prometheus instance allowing it to be scraped from another cluster. For more details, continue reading here.

Typically, this is not necessary, but in case an extension wants to extend the configuration for this aggregate Prometheus, they can create the prometheus-operator’s custom resources and label them with prometheus=aggregate, for example:

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  labels:
    prometheus: aggregate
  name: aggregate-my-component
  namespace: garden
spec:
  selector:
    matchLabels:
      app: my-component
  endpoints:
  - metricRelabelings:
    - action: keep
      regex: ^(metric1|metric2|...)$
      sourceLabels:
      - __name__
    port: metrics

Shoot Cluster Prometheus

The shoot-specific metrics are then made available to operators and users in the shoot Plutono, using the shoot Prometheus as data source.

Extension controllers might deploy components as part of their reconciliation next to the shoot’s control plane. Examples for this would be a cloud-controller-manager or CSI controller deployments. Extensions that want to have their managed control plane components integrated with monitoring can contribute their per-shoot configuration for scraping Prometheus metrics, Alertmanager alerts or Plutono dashboards.

Extensions Monitoring Integration

Before deploying the shoot-specific Prometheus instance, Gardener will read all ConfigMaps in the shoot namespace, which are labeled with extensions.gardener.cloud/configuration=monitoring. Such ConfigMaps may contain four fields in their data:

  • scrape_config: This field contains Prometheus scrape configuration for the component(s) and metrics that shall be scraped.
  • alerting_rules: This field contains Alertmanager rules for alerts that shall be raised.
  • dashboard_operators: This field contains a Plutono dashboard in JSON. Note that the former field name was kept for backwards compatibility but the dashboard is going to be shown both for Gardener operators and for shoot owners because the monitoring stack no longer distinguishes the two roles.
  • dashboard_users: This field contains a Plutono dashboard in JSON. Note that the former field name was kept for backwards compatibility but the dashboard is going to be shown both for Gardener operators and for shoot owners because the monitoring stack no longer distinguishes the two roles.

Example: A ControlPlane controller deploying a cloud-controller-manager into the shoot namespace wants to integrate monitoring configuration for scraping metrics, alerting rules, dashboards, and logging configuration for exposing logs to the end users.

apiVersion: v1
kind: ConfigMap
metadata:
  name: extension-controlplane-monitoring-ccm
  namespace: shoot--project--name
  labels:
    extensions.gardener.cloud/configuration: monitoring
data:
  scrape_config: |
    - job_name: cloud-controller-manager
      scheme: https
      tls_config:
        insecure_skip_verify: true
      authorization:
        type: Bearer
        credentials_file: /var/run/secrets/gardener.cloud/shoot/token/token
      honor_labels: false
      kubernetes_sd_configs:
      - role: endpoints
        namespaces:
          names: [shoot--project--name]
      relabel_configs:
      - source_labels:
        - __meta_kubernetes_service_name
        - __meta_kubernetes_endpoint_port_name
        action: keep
        regex: cloud-controller-manager;metrics
      # common metrics
      - action: labelmap
        regex: __meta_kubernetes_service_label_(.+)
      - source_labels: [ __meta_kubernetes_pod_name ]
        target_label: pod
      metric_relabel_configs:
      - process_max_fds
      - process_open_fds    

  alerting_rules: |
    cloud-controller-manager.rules.yaml: |
      groups:
      - name: cloud-controller-manager.rules
        rules:
        - alert: CloudControllerManagerDown
          expr: absent(up{job="cloud-controller-manager"} == 1)
          for: 15m
          labels:
            service: cloud-controller-manager
            severity: critical
            type: seed
            visibility: all
          annotations:
            description: All infrastructure specific operations cannot be completed (e.g. creating load balancers or persistent volumes).
            summary: Cloud controller manager is down.    

Logging

In Kubernetes clusters, container logs are non-persistent and do not survive stopped and destroyed containers. Gardener addresses this problem for the components hosted in a seed cluster by introducing its own managed logging solution. It is integrated with the Gardener monitoring stack to have all troubleshooting context in one place.

&ldquo;Cluster Logging Topology&rdquo;

Gardener logging consists of components in three roles - log collectors and forwarders, log persistency and exploration/consumption interfaces. All of them live in the seed clusters in multiple instances:

  • Logs are persisted by Vali instances deployed as StatefulSets - one per shoot namespace, if the logging is enabled in the gardenlet configuration (logging.enabled) and the shoot purpose is not testing, and one in the garden namespace. The shoot instances store logs from the control plane components hosted there. The garden Vali instance is responsible for logs from the rest of the seed namespaces - kube-system, garden, extension-*, and others.
  • Fluent-bit DaemonSets deployed by the fluent-operator on each seed node collect logs from it. A custom plugin takes care to distribute the collected log messages to the Vali instances that they are intended for. This allows to fetch the logs once for the whole cluster, and to distribute them afterwards.
  • Plutono is the UI component used to explore monitoring and log data together for easier troubleshooting and in context. Plutono instances are configured to use the corresponding Vali instances, sharing the same namespace as data providers. There is one Plutono Deployment in the garden namespace and one Deployment per shoot namespace (exposed to the end users and to the operators).

Logs can be produced from various sources, such as containers or systemd, and in different formats. The fluent-bit design supports configurable data pipeline to address that problem. Gardener provides such configuration for logs produced by all its core managed components as ClusterFilters and ClusterParsers . Extensions can contribute their own, specific configurations as fluent-operator custom resources too. See for example the logging configuration for the Gardener AWS provider extension.

Fluent-bit Log Parsers and Filters

To integrate with Gardener logging, extensions can and should specify how fluent-bit will handle the logs produced by the managed components that they contribute to Gardener. Normally, that would require to configure a parser for the specific logging format, if none of the available is applicable, and a filter defining how to apply it. For a complete reference for the configuration options, refer to fluent-bit’s documentation.

To contribute its own configuration to the fluent-bit agents data pipelines, an extension must deploy a fluent-operator custom resource labeled with fluentbit.gardener/type: seed in the seed cluster.

Note: Take care to provide the correct data pipeline elements in the corresponding fields and not to mix them.

Example: Logging configuration for provider-specific cloud-controller-manager deployed into shoot namespaces that reuses the kube-apiserver-parser defined in logging.go to parse the component logs:

apiVersion: fluentbit.fluent.io/v1alpha2
kind: ClusterFilter
metadata:
  labels:
    fluentbit.gardener/type: "seed"
  name: cloud-controller-manager-aws-cloud-controller-manager
spec:
  filters:
  - parser:
      keyName: log
      parser: kube-apiserver-parser
      reserveData: true
  match: kubernetes.*cloud-controller-manager*aws-cloud-controller-manager*

Further details how to define parsers and use them with examples can be found in the following guide.

Plutono

The two types of Plutono instances found in a seed cluster are configured to expose logs of different origin in their dashboards:

  • Garden Plutono dashboards expose logs from non-shoot namespaces of the seed clusters
  • Shoot Plutono dashboards expose logs from the shoot cluster namespace where they belong
    • Kube Apiserver
    • Kube Controller Manager
    • Kube Scheduler
    • Cluster Autoscaler
    • VPA components
    • Kubernetes Pods

If the type of logs exposed in the Plutono instances needs to be changed, it is necessary to update the corresponding instance dashboard configurations.

Tips

  • Be careful to create ClusterFilters and ClusterParsers with unique names because they are not namespaced. We use pod_name for filters with one container and pod_name--container_name for pods with multiple containers.
  • Be careful to match exactly the log names that you need for a particular parser in your filters configuration. The regular expression you will supply will match names in the form kubernetes.pod_name.<metadata>.container_name. If there are extensions with the same container and pod names, they will all match the same parser in a filter. That may be a desired effect, if they all share the same log format. But it will be a problem if they don’t. To solve it, either the pod or container names must be unique, and the regular expression in the filter has to match that unique pattern. A recommended approach is to prefix containers with the extension name and tune the regular expression to match it. For example, using myextension-container as container name and a regular expression kubernetes.mypod.*myextension-container will guarantee match of the right log name. Make sure that the regular expression does not match more than you expect. For example, kubernetes.systemd.*systemd.* will match both systemd-service and systemd-monitor-service. You will want to be as specific as possible.
  • It’s a good idea to put the logging configuration into the Helm chart that also deploys the extension controller, while the monitoring configuration can be part of the Helm chart/deployment routine that deploys the component managed by the controller.

References and Additional Resources