188 lines
7.0 KiB
YAML
188 lines
7.0 KiB
YAML
apiVersion: apps/v1
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kind: StatefulSet
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metadata:
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name: fancy-dns
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namespace: dns
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labels:
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app.kubernetes.io/name: fancy-dns
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annotations:
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k8s-helper.io/git-url: "https://git.k6n.net/mats/fancy-dns"
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k8s-helper.io/git-ssh: "git@git.k6n.net:mats/fancy-dns.git"
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spec:
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serviceName: fancy-dns
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# A StatefulSet rather than a Deployment because each pod owns a PVC (the
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# cache snapshot and the query log are per-pod state worth keeping across a
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# reschedule). The flip side: the HPA does not work on a StatefulSet — the
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# controller and the autoscaler fight over the replica count — so scaling
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# means adding nodes and replicas here, not CPU targets.
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replicas: 2
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podManagementPolicy: Parallel
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selector:
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matchLabels:
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app.kubernetes.io/name: fancy-dns
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template:
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metadata:
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labels:
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app.kubernetes.io/name: fancy-dns
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annotations:
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k8s-helper.io/git-url: "https://git.k6n.net/mats/fancy-dns"
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k8s-helper.io/git-ssh: "git@git.k6n.net:mats/fancy-dns.git"
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# A config change is a SIGHUP, not a restart: the server re-reads the
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# file and hot-swaps every component. This annotation is for
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# stakater/reloader-class controllers; without one, `kubectl rollout
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# restart` is the manual equivalent.
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reloader.stakater.com/auto: "true"
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spec:
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serviceAccountName: fancy-dns
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imagePullSecrets:
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- name: reg-k6n
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# No hostNetwork. The server does not set SO_REUSEPORT, so a second
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# host-network pod would fail to bind :53 and crash-loop; the ports are
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# served by a LoadBalancer Service instead (see 20-service.yaml).
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dnsPolicy: ClusterFirst
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# The app drains in-flight queries for up to 15s on SIGTERM (see the
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# shutdown timeout in cmd/fancy-dns/main.go); give it room beyond that.
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terminationGracePeriodSeconds: 30
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securityContext:
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runAsNonRoot: true
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runAsUser: 65532
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runAsGroup: 65532
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fsGroup: 65532
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seccompProfile:
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type: RuntimeDefault
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topologySpreadConstraints:
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- maxSkew: 1
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topologyKey: kubernetes.io/hostname
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whenUnsatisfiable: ScheduleAnyway
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labelSelector:
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matchLabels:
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app.kubernetes.io/name: fancy-dns
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containers:
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- name: fancy-dns
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image: registry.k6n.net/fancydns
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imagePullPolicy: Always
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args:
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- -config
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- /etc/fancy-dns/config.yaml
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env:
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# Substituted into the config by the loader, so the admin API key
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# comes from the Secret and not from the ConfigMap.
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- name: FANCYDNS_API_KEY
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valueFrom:
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secretKeyRef:
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name: fancy-dns-apikey
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key: api-key
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ports:
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- name: dns-udp
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containerPort: 53
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protocol: UDP
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- name: dns-tcp
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containerPort: 53
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protocol: TCP
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- name: dot
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containerPort: 853
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protocol: TCP
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- name: doh
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containerPort: 443
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protocol: TCP
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- name: admin
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containerPort: 8080
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protocol: TCP
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securityContext:
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allowPrivilegeEscalation: false
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readOnlyRootFilesystem: true
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capabilities:
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drop: ["ALL"]
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# Only because of the low ports. The pod is not privileged and
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# has no other capability left; drop the Service and the
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# Capability together if you move the listeners off 53/443.
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add: ["NET_BIND_SERVICE"]
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# Liveness: the process is up. /api/healthz is unauthenticated on
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# purpose, because a probe cannot carry an API key.
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livenessProbe:
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httpGet:
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path: /api/healthz
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port: admin
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initialDelaySeconds: 5
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periodSeconds: 20
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# Readiness: the listener is actually bound, so the Service does not
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# send traffic to a pod that is still binding.
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readinessProbe:
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httpGet:
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path: /api/healthz
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port: admin
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initialDelaySeconds: 3
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periodSeconds: 5
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failureThreshold: 2
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# Startup: binding the listeners and fetching the first blocklist
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# can take a while on a cold node, so give it room before the
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# liveness probe starts killing it.
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startupProbe:
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httpGet:
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path: /api/healthz
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port: admin
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periodSeconds: 3
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failureThreshold: 30
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resources:
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requests:
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cpu: 250m
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memory: 256Mi
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limits:
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# No CPU limit on purpose: a DNS server that gets throttled
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# turns into dropped queries, which is worse than a noisy
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# neighbour. The memory limit is the one that matters, because
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# the cache is sized in entries.
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memory: 1Gi
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volumeMounts:
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- name: config
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mountPath: /etc/fancy-dns/config.yaml
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subPath: config.yaml
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readOnly: true
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- name: zones
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mountPath: /etc/fancy-dns/zones
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readOnly: true
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- name: tls
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mountPath: /etc/fancy-dns/tls
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readOnly: true
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- name: data
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mountPath: /var/lib/fancy-dns
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- name: tmp
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mountPath: /tmp
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volumes:
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- name: config
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configMap:
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name: fancy-dns-config
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# Local zones are ordinary master files; ship them in a ConfigMap or
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# edit them in the mounted volume. There is no zone API — the admin API
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# drives blocklists, the cache and the query log, not the zone files.
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# the data volume. Optional because the glob in the config matches
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# nothing cleanly.
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- name: zones
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configMap:
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name: fancy-dns-zones
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optional: true
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- name: tls
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secret:
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secretName: fancy-dns-tls
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- name: tmp
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emptyDir: {}
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volumeClaimTemplates:
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# Cache snapshot (cache.persist.path) and query log (qlog.path) live here,
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# along with downloaded blocklists. ReadWriteOnce is per-pod: a pod keeps
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# its own cache across a reschedule, which is the whole point of the
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# snapshot, but it cannot be shared between replicas.
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#
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# Sizing: cache.size is an entry count, not bytes, so disk usage has to be
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# estimated. A packed A/AAAA answer with a small authority section is
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# roughly 300-600 bytes on the wire and nearer 1 kB resident, so 500k
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# entries lands around 500 MB; qlog is the other consumer (see
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# qlog.max_entries). 4Gi leaves room for both plus a re-fetched list.
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- metadata:
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name: data
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spec:
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storageClassName: nfs-large
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accessModes: ["ReadWriteOnce"]
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resources:
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requests:
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storage: 4Gi
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