Configure Alerts Using AlertManager

To keep your clusters and applications healthy and drive productivity forward, you need to stay informed of all events occurring in your cluster. DKP helps you to stay informed of these events by using the alertmanager of the kube-prometheus-stack.

Kommander is configured with pre-defined alerts to monitor four specific events. You receive alerts related to:

State of your nodes
System services managing the Kubernetes cluster
Resource events from specific system services
Prometheus expressions exceeding some pre-defined thresholds

Some examples of the alerts currently available are:

CPUThrottlingHigh
TargetDown
KubeletNotReady
KubeAPIDown
CoreDNSDown
KubeVersionMismatch

A complete list with all the pre-defined alerts can be found on GitHub.

Prerequisites

Determine the name of the workspace where you wish to perform the actions. You can use the dkp get workspaces command to see the list of workspace names and their corresponding namespaces.
Set the WORKSPACE_NAMESPACE environment variable to the name of the workspace’s namespace where the cluster is attached:
CODE
```
export WORKSPACE_NAMESPACE=<workspace_namespace>
```

Configure Alert Rules

Use override ConfigMaps to configure alert rules.

You can enable or disable the default alert rules by providing the desired configuration in an overrides ConfigMap. For example, if you want to disable the default node alert rules, follow these steps to define an overrides ConfigMap:

Create a file named kube-prometheus-stack-overrides.yaml and paste the following YAML code into it to create the overrides ConfigMap:

CODE

apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-prometheus-stack-overrides
  namespace: ${WORKSPACE_NAMESPACE}
data:
 values.yaml: |
   ---
   defaultRules:
     rules:
       node: false

Use the following command to apply the YAML file:

CODE

kubectl apply -f kube-prometheus-stack-overrides.yaml

Edit the kube-prometheus-stack AppDeployment to replace the spec.configOverrides.name value with kube-prometheus-stack-overrides. (You can use the steps in the procedure, Deploy an application with a custom configuration as a guide.)

CODE

dkp edit appdeployment -n ${WORKSPACE_NAMESPACE} kube-prometheus-stack

After your editing is complete, the AppDeployment resembles this example:

CODE

apiVersion: apps.kommander.d2iq.io/v1alpha2
kind: AppDeployment
metadata:
  name: kube-prometheus-stack
  namespace: ${WORKSPACE_NAMESPACE}
spec:
  appRef:
    name: kube-prometheus-stack-34.9.3
    kind: ClusterApp
  configOverrides:
    name: kube-prometheus-stack-overrides

To disable all rules, create an overrides ConfigMap with this YAML code:

CODE

apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-prometheus-stack-overrides
  namespace: ${WORKSPACE_NAMESPACE}
data:
 values.yaml: |
   ---
   defaultRules:
     create: false

Alert rules for the Velero platform service are turned off by default. You can enable them with the following overrides ConfigMap. They should be enabled only if the velero platform service is enabled. If platform services are disabled disable the alert rules to avoid alert misfires.
CODE
```
apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-prometheus-stack-overrides
  namespace: ${WORKSPACE_NAMESPACE}
data:
  values.yaml: |
    ---
    mesosphereResources:
      rules:
        velero: true
```

To create a custom alert rule named my-rule-name, create the overrides ConfigMap with this YAML code:

CODE

apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-prometheus-stack-overrides
  namespace: ${WORKSPACE_NAMESPACE}
data:
  values.yaml: |
    ---
    additionalPrometheusRulesMap:
      my-rule-name:
        groups:
        - name: my_group
          rules:
          - record: my_record
            expr: 100 * my_record

After you set up your alerts, you can manage each alert using the Prometheus web console to mute or unmute firing alerts, and perform other operations. For more information about configuring alertmanager, see the Prometheus website.

To access the Prometheus Alertmanager UI, browse to the landing page and then search for the Prometheus Alertmanager dashboard, for example https://<CLUSTER_URL>/dkp/alertmanager.

Notify Prometheus Alerts in Slack

To hook up the Prometheus alertmanager notification system, you need to overwrite the existing configuration.

The following file, named alertmanager.yaml, configures alertmanager to use the Incoming Webhooks feature of Slack (slack_api_url: https://hooks.slack.com/services/<HOOK_ID>) to fire all the alerts to a specific channel #MY-SLACK-CHANNEL-NAME.

CODE

global:
  resolve_timeout: 5m
  slack_api_url: https://hooks.slack.com/services/<HOOK_ID>

route:
  group_by: ['alertname']
  group_wait: 2m
  group_interval: 5m
  repeat_interval: 1h

  # If an alert isn't caught by a route, send it to slack.
  receiver: slack_general
  routes:
    - match:
        alertname: Watchdog
      receiver: "null"

receivers:
  - name: "null"
  - name: slack_general
    slack_configs:
      - channel: '#MY-SLACK-CHANNEL-NAME'
        icon_url: https://avatars3.githubusercontent.com/u/3380462
        send_resolved: true
        color: '{{ if eq .Status "firing" }}danger{{ else }}good{{ end }}'
        title: '{{ template "slack.default.title" . }}'
        title_link: '{{ template "slack.default.titlelink" . }}'
        pretext: '{{ template "slack.default.pretext" . }}'
        text: '{{ template "slack.default.text" . }}'
        fallback: '{{ template "slack.default.fallback" . }}'
        icon_emoji: '{{ template "slack.default.iconemoji" . }}'

templates:
  - '*.tmpl'

The following file, named notification.tmpl, is a template that defines a pretty format for the fired notifications:

CODE

{{ define "__titlelink" }}
{{ .ExternalURL }}/#/alerts?receiver={{ .Receiver }}
{{ end }}

{{ define "__title" }}
[{{ .Status | toUpper }}{{ if eq .Status "firing" }}:{{ .Alerts.Firing | len }}{{ end }}] {{ .GroupLabels.SortedPairs.Values | join " " }}
{{ end }}

{{ define "__text" }}
{{ range .Alerts }}
{{ range .Labels.SortedPairs }}*{{ .Name }}*: `{{ .Value }}`
{{ end }} {{ range .Annotations.SortedPairs }}*{{ .Name }}*: {{ .Value }}
{{ end }} *source*: {{ .GeneratorURL }}
{{ end }}
{{ end }}

{{ define "slack.default.title" }}{{ template "__title" . }}{{ end }}
{{ define "slack.default.username" }}{{ template "__alertmanager" . }}{{ end }}
{{ define "slack.default.fallback" }}{{ template "slack.default.title" . }} | {{ template "slack.default.titlelink" . }}{{ end }}
{{ define "slack.default.pretext" }}{{ end }}
{{ define "slack.default.titlelink" }}{{ template "__titlelink" . }}{{ end }}
{{ define "slack.default.iconemoji" }}{{ end }}
{{ define "slack.default.iconurl" }}{{ end }}
{{ define "slack.default.text" }}{{ template "__text" . }}{{ end }}

Finally, apply these changes to alertmanager as follows. Set ${WORKSPACE_NAMESPACE} to the workspace namespace that kube-prometheus-stack is deployed in:

CODE

kubectl create secret generic -n ${WORKSPACE_NAMESPACE} \
  alertmanager-kube-prometheus-stack-alertmanager \
  --from-file=alertmanager.yaml \
  --from-file=notification.tmpl \
  --dry-run=client --save-config -o yaml | kubectl apply -f -