On Kubernetes

A RuleGroup renders the same way into every destination, so the rules are declared once however Prometheus loads them.

Into a Prometheus Operator PrometheusRule

Put the groups in spec.groups. The k8s serializer writes each one as the group the rule file would hold.

import { PrometheusRule } from "@intentius/chant-lexicon-k8s";
import { RuleGroup, type Rule } from "@intentius/chant-lexicon-prometheus";

const rules: Rule[] = [
  { alert: "ApiDown", expr: 'up{job="api"} == 0', for: "5m", labels: { severity: "page" }, annotations: { summary: "api is down" } },
];
const api = new RuleGroup({ name: "api", rules });

export const apiRules = new PrometheusRule({
  metadata: { name: "api-rules", labels: { release: "kube-prometheus-stack" } },
  spec: { groups: [api] },
});

Leave the group unexported (as above) when it should appear only inside the CRD. Export it too, and the build also writes it to the rule file.

Through MonitoredService

import { MonitoredService } from "@intentius/chant-lexicon-k8s";

export const svc = MonitoredService({ name: "api", image: "api:1.0", ruleGroups: [api] });

ruleGroups takes RuleGroups or plain group objects. The older alertRules prop still works and renders as before; when both are set, the alertRules group comes first.

Without the operator

For Prometheus and Alertmanager run as plain Deployments, put the files in ConfigMaps. ruleFileYaml and alertmanagerYaml return exactly what the serializer writes:

import { ConfiguredApp } from "@intentius/chant-lexicon-k8s";
import { alertmanagerYaml, ruleFileYaml } from "@intentius/chant-lexicon-prometheus";
import { stack } from "./rules";
import { root } from "./alertmanager";

const prometheus = ConfiguredApp({
  name: "prometheus",
  image: "prom/prometheus:v3.15.0",
  port: 9090,
  configData: { "prometheus.yml": prometheusYml, "rules.yml": ruleFileYaml([stack]) },
  configMountPath: "/etc/prometheus",
});

const alertmanager = ConfiguredApp({
  name: "alertmanager",
  image: "prom/alertmanager:v0.34.1",
  port: 9093,
  configData: { "alertmanager.yml": alertmanagerYaml([root]) },
  configMountPath: "/etc/alertmanager",
});

The k3d-stack example is this, with an e2e run that brings it up on k3d.

Build the two outputs separately so the k8s file is appliable on its own:

chant build src --lexicon k8s -o dist/k8s.yaml
chant build src --lexicon prometheus -o dist/rules.yml