VictoriaMetrics/docs/operator/design.md

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Design

This document describes the design and interaction between the custom resource definitions (CRD) that the Victoria Metrics Operator introduces.

Operator introduces the following custom resources:

• VMSingle
• VMCluster
• VMAgent
• VMAlert
• VMServiceScrape
• VMPodScrape
• VMAlertmanager
• VMAlertmanagerConfig
• VMRule
• VMPrometheusConverter
• VMProbe
• VMNodeScrape
• VMStaticScrape
• VMAuth
• VMUser

VMSingle

The VMSingle CRD declaratively defines a single-node VM installation to run in a Kubernetes cluster.

For each VMSingle resource, the Operator deploys a properly configured Deployment in the same namespace. The VMSingle Pods are configured to mount an empty dir or PersistentVolumeClaimSpec for storing data. Deployment update strategy set to recreate. No more than one replica allowed.

For each VMSingle resource, the Operator adds Service and VMServiceScrape in the same namespace prefixed with name <VMSingle-name>.

VMCluster

The VMCluster CRD defines a cluster version VM.

For each VMCluster resource, the Operator creates VMStorage as StatefulSet, VMSelect as StatefulSet and VMInsert as deployment. For VMStorage and VMSelect headless services are created. VMInsert is created as service with clusterIP.

There is a strict order for these objects creation and reconciliation:

1. VMStorage is synced - the Operator waits until all its pods are ready;
2. Then it syncs VMSelect with the same manner;
3. VMInsert is the last object to sync.

All statefulsets are created with OnDelete update type. It allows to manually manage the rolling update process for Operator by deleting pods one by one and waiting for the ready status.

Rolling update process may be configured by the operator env variables. The most important is VM_PODWAITREADYTIMEOUT=80s - it controls how long to wait for pod's ready status.

VMAgent

The VMAgent CRD declaratively defines a desired VMAgent setup to run in a Kubernetes cluster.

For each VMAgent resource Operator deploys a properly configured Deployment in the same namespace. The VMAgent Pods are configured to mount a Secret prefixed with <VMAgent-name> containing the configuration for VMAgent.

For each VMAgent resource, the Operator adds Service and VMServiceScrape in the same namespace prefixed with name <VMAgent-name>.

The CRD specifies which VMServiceScrape should be covered by the deployed VMAgent instances based on label selection. The Operator then generates a configuration based on the included VMServiceScrapes and updates the Secret which contains the configuration. It continuously does so for all changes that are made to the VMServiceScrapes or the VMAgent resource itself.

If no selection of VMServiceScrapes is provided - Operator leaves management of the Secret to the user, so user can set custom configuration while still benefiting from the Operator's capabilities of managing VMAgent setups.

VMAlert

The VMAlert CRD declaratively defines a desired VMAlert setup to run in a Kubernetes cluster.

For each VMAlert resource, the Operator deploys a properly configured Deployment in the same namespace. The VMAlert Pods are configured to mount a list of Configmaps prefixed with <VMAlert-name>-number containing the configuration for alerting rules.

For each VMAlert resource, the Operator adds Service and VMServiceScrape in the same namespace prefixed with name <VMAlert-name>.

The CRD specifies which VMRules should be covered by the deployed VMAlert instances based on label selection. The Operator then generates a configuration based on the included VMRules and updates the Configmaps containing the configuration. It continuously does so for all changes that are made to VMRules or to the VMAlert resource itself.

Alerting rules are filtered by selector ruleNamespaceSelector in VMAlert CRD definition. For selecting rules from all namespaces you must specify it to empty value:

spec:
 ruleNamespaceSelector: {}

VMServiceScrape

The VMServiceScrape CRD allows to define a dynamic set of services for monitoring. Services and scraping configurations can be matched via label selections. This allows an organization to introduce conventions for how metrics should be exposed. Following these conventions new services will be discovered automatically without need to reconfigure.

Monitoring configuration based on discoveryRole setting. By default, endpoints is used to get objects from kubernetes api. It's also possible to use discoveryRole: service or discoveryRole: endpointslices

Endpoints objects are essentially lists of IP addresses. Typically, Endpoints objects are populated by Service object. Service object discovers Pods by a label selector and adds those to the Endpoints object.

A Service may expose one or more service ports backed by a list of one or multiple endpoints pointing to specific Pods. The same reflected in the respective Endpoints object as well.

The VMServiceScrape object discovers Endpoints objects and configures VMAgent to monitor Pods.

The Endpoints section of the VMServiceScrapeSpec is used to configure which Endpoints ports should be scraped. For advanced use cases, one may want to monitor ports of backing Pods, which are not a part of the service endpoints. Therefore, when specifying an endpoint in the endpoints section, they are strictly used.

Note: endpoints (lowercase) is the field in the VMServiceScrape CRD, while Endpoints (capitalized) is the Kubernetes object kind.

Both VMServiceScrape and discovered targets may belong to any namespace. It is important for cross-namespace monitoring use cases, e.g. for meta-monitoring. Using the serviceScrapeSelector of the VMAgentSpec one can restrict the namespaces from which VMServiceScrapes are selected from by the respective VMAgent server. Using the namespaceSelector of the VMServiceScrape one can restrict the namespaces from which Endpoints can be discovered from. To discover targets in all namespaces the namespaceSelector has to be empty:

spec:
  namespaceSelector: {}

VMPodScrape

The VMPodScrape CRD allows to declaratively define how a dynamic set of pods should be monitored. Use label selections to match pods for scraping. This allows an organization to introduce conventions for how metrics should be exposed. Following these conventions new services will be discovered automatically without need to reconfigure.

A Pod is a collection of one or more containers which can expose Prometheus metrics on a number of ports.

The VMPodScrape object discovers pods and generates the relevant scraping configuration.

The PodMetricsEndpoints section of the VMPodScrapeSpec is used to configure which ports of a pod are going to be scraped for metrics and with which parameters.

Both VMPodScrapes and discovered targets may belong to any namespace. It is important for cross-namespace monitoring use cases, e.g. for meta-monitoring. Using the namespaceSelector of the VMPodScrapeSpec one can restrict the namespaces from which Pods are discovered from. To discover targets in all namespaces the namespaceSelector has to be empty:

spec:
  namespaceSelector:
    any: true

VMAlertmanager

The VMAlertmanager CRD declaratively defines a desired Alertmanager setup to run in a Kubernetes cluster. It provides options to configure replication and persistent storage.

For each Alertmanager resource, the Operator deploys a properly configured StatefulSet in the same namespace. The Alertmanager pods are configured to include a Secret called <alertmanager-name> which holds the used configuration file in the key alertmanager.yaml.

When there are two or more configured replicas the Operator runs the Alertmanager instances in high availability mode.

VMAlertmanagerConfig

The VMAlertmanagerConfig provides way to configure VMAlertmanager configuration with CRD. It allows to define different configuration parts, which will be merged by operator into config. It behaves like other config parts - VMServiceScrape and etc.

VMRule

The VMRule CRD declaratively defines a desired Prometheus rule to be consumed by one or more VMAlert instances.

Alerts and recording rules can be saved and applied as YAML files, and dynamically loaded without requiring any restart.

VMPrometheusConverter

By default, the Operator converts and updates existing prometheus-operator API objects:

ServiceMonitor into VMServiceScrape PodMonitor into VMPodScrape PrometheusRule into VMRule Probe into VMProbe Removing prometheus-operator API objects wouldn't delete any converted objects. So you can safely migrate or run two operators at the same time.

VMProbe

The VMProbe CRD provides probing target ability with a prober. The most common prober is blackbox exporter. By specifying configuration at CRD, operator generates config for VMAgent and syncs it. It's possible to use static targets or use standard k8s discovery mechanism with Ingress. You have to configure blackbox exporter before you can use this feature. The second requirement is VMAgent selectors, it must match your VMProbe by label or namespace selector.

VMNodeScrape

The VMNodeScrape CRD provides discovery mechanism for scraping metrics kubernetes nodes. By specifying configuration at CRD, operator generates config for VMAgent and syncs it. It's useful for cadvisor scraping, node-exporter or other node-based exporters. VMAgent nodeScrapeSelector must match VMNodeScrape labels.

VMStaticScrape

The VMStaticScrape CRD provides mechanism for scraping metrics from static targets, configured by CRD targets. By specifying configuration at CRD, operator generates config for VMAgent and syncs it. It's useful for external targets management, when service-discovery is not available. VMAgent staticScrapeSelector must match VMStaticScrape labels.

VMAuth

The VMAuth CRD provides mechanism for exposing application with authorization to outside world or to other applications inside kubernetes cluster. For first case, user can configure ingress setting at VMAuth CRD. For second one, operator will create secret with username and password at VMUser CRD name. So it will be possible to access these credentials from any application by targeting corresponding kubernetes secret.

VMUser

The VMUser CRD describes user configuration, its authentication methods basic auth or Authorization header. User access permissions, with possible routing information. User can define routing target with static config, by entering target url, or with CRDRef, in this case, operator queries kubernetes API, retrieves information about CRD and builds proper url.