v-m: Deploy (clustered) Victoria Metrics

Since *mtrcs0.pyrocufflink.blue* (the Metrics Pi) seems to be dying,
I decided to move monitoring and alerting into Kubernetes.

I was originally planning to have a single, dedicated virtual machine
for Victoria Metrics and Grafana, similar to how the Metrics Pi was set
up, but running Fedora CoreOS instead of a custom Buildroot-based OS.
While I was working on the Ignition configuration for the VM, it
occurred to me that monitoring would be interrupted frequently, since
FCOS updates weekly and all updates require a reboot.  I would rather
not have that many gaps in the data.  Ultimately I decided that
deploying a cluster with Kubernetes would probably be more robust and
reliable, as updates can be performed without any downtime at all.

I chose not to use the Victoria Metrics Operator, but rather handle
the resource definitions myself.  Victoria Metrics components are not
particularly difficult to deploy, so the overhead of running the
operator and using its custom resources would not be worth the minor
convenience it provides.

victoria-metrics/vmalert.yaml

@@ -0,0 +1,88 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: vmalert
+  labels:
+    app.kubernetes.io/name: vmalert
+    app.kubernetes.io/component: vmalert
+spec:
+  ports:
+  - port: 8880
+    name: vmalert
+  selector:
+    app.kubernetes.io/name: vmalert
+    app.kubernetes.io/component: vmalert
+
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: vmalert
+  labels:
+    app.kubernetes.io/name: vmalert
+    app.kubernetes.io/component: vmalert
+spec:
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: vmalert
+      app.kubernetes.io/component: vmalert
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: vmalert
+        app.kubernetes.io/component: vmalert
+    spec:
+      containers:
+      - name: vmalert
+        image: docker.io/victoriametrics/vmalert:v1.96.0
+        args:
+        - -envflag.enable=true
+        - -envflag.prefix=vmalert_
+        - -httpListenAddr=0.0.0.0:8880
+        - -configCheckInterval=30s
+        env:
+        - name: vmalert_rule
+          value: /rules/*.yml
+        - name: vmalert_datasource_url
+          value: http://vmselect:8481/select/1/prometheus
+        - name: vmalert_remoteread_url
+          value: http://vmselect:8481/select/1/prometheus
+        - name: vmalert_remorewrite_url
+          value: http://vminsert:8480/select/1/prometheus
+        - name: vmalert_notifier_url
+          value: http://alertmanager:9093
+        ports:
+        - containerPort: 8880
+          name: http
+        readinessProbe: &probe
+          httpGet:
+            port: http
+            path: /health
+          periodSeconds: 60
+        startupProbe:
+          <<: *probe
+          periodSeconds: 1
+          successThreshold: 1
+          failureThreshold: 30
+          timeoutSeconds: 1
+        securityContext:
+          runAsNonRoot: true
+          readOnlyRootFilesystem: true
+        volumeMounts:
+        - mountPath: /rules
+          name: rules
+          readOnly: true
+        - mountPath: /tmp
+          name: tmp
+          subPath: tmp
+      securityContext:
+        runAsGroup: 2093
+        runAsNonRoot: true
+        runAsUser: 2093
+      volumes:
+      - name: rules
+        configMap:
+          name: vmalert-rules
+          optional: true
+      - name: tmp
+        emptyDir: {}