Building a Microservice for my Hugo Blog on k3s

A self-hosted view counter for a static Hugo blog — built from scratch in Python, containerized, signed, deployed to k3s via GitOps, and integrated into the Hugo frontend. No third-party services. Every piece runs in the cluster.

Architecture

Visitor loads post
    ↓
Hugo frontend JS → POST /views/{slug} → view-counter API
                → GET  /views/{slug} → display count
                         ↓
                   FastAPI (Python)
                         ↓
                   PostgreSQL (CNPG)
                   2 instances, WAL archiving to MinIO

CI/CD flow:

git push → Forgejo CI
    → multi-stage Docker build
    → Cosign image signing
    → pi5cluster repo image digest update
    → Flux GitOps reconciles
    → Kubernetes rolling deployment

Python Application

The service is built with FastAPI and asyncpg, managed with uv and structured as a proper Python package.

Project structure:

view-counter/
├── src/
│   └── view_counter/
│       ├── __init__.py
│       ├── app.py
│       ├── database.py
│       └── routes.py
├── main.py
├── pyproject.toml
├── uv.lock
├── Dockerfile
└── .forgejo/
    └── workflows/
        └── build.yml

pyproject.toml:

[project]
name = "view-counter"
version = "0.1.0"
description = "View counter microservice for uclab.dev"
requires-python = ">=3.12"
dependencies = [
    "asyncpg>=0.31.0",
    "fastapi>=0.135.1",
    "python-dotenv>=1.2.2",
    "uvicorn>=0.42.0",
]

[dependency-groups]
dev = [
    "httpx>=0.28.1",
    "pytest>=9.0.2",
    "pytest-asyncio>=1.3.0",
]

[tool.pytest.ini_options]
asyncio_mode = "auto"
testpaths = ["tests"]

src/view_counter/database.py:

import asyncpg
import os

_pool: asyncpg.Pool | None = None


async def get_pool() -> asyncpg.Pool:
    global _pool
    if _pool is None:
        _pool = await asyncpg.create_pool(
            host=os.getenv("DB_HOST", "localhost"),
            port=int(os.getenv("DB_PORT", 5432)),
            database=os.getenv("DB_NAME", "view-counter"),
            user=os.getenv("DB_USER", "view-counter"),
            password=os.getenv("DB_PASSWORD", ""),
            min_size=2,
            max_size=10,
        )
    return _pool


async def init_db() -> None:
    try:
        pool = await get_pool()
        async with pool.acquire() as conn:
            await conn.execute("""
                CREATE TABLE IF NOT EXISTS views (
                    slug        TEXT PRIMARY KEY,
                    count       BIGINT NOT NULL DEFAULT 0,
                    last_seen   TIMESTAMPTZ NOT NULL DEFAULT now()
                )
            """)
    except Exception as e:
        print(f"WARNING: DB not available: {e}")
        print("App starting without DB — endpoints will fail until DB is reachable")


async def close_pool() -> None:
    global _pool
    if _pool is not None:
        await _pool.close()
        _pool = None

src/view_counter/routes.py:

from fastapi import APIRouter
from .database import get_pool

router = APIRouter()


@router.get("/health")
async def health():
    return {"status": "ok"}


@router.get("/views")
async def get_all_views():
    pool = await get_pool()
    async with pool.acquire() as conn:
        rows = await conn.fetch(
            "SELECT slug, count FROM views ORDER BY count DESC"
        )
    return [{"slug": r["slug"], "count": r["count"]} for r in rows]


@router.get("/views/{slug:path}")
async def get_views(slug: str):
    pool = await get_pool()
    async with pool.acquire() as conn:
        row = await conn.fetchrow(
            "SELECT count FROM views WHERE slug = $1", slug
        )
    return {"slug": slug, "count": row["count"] if row else 0}


@router.post("/views/{slug:path}")
async def increment_views(slug: str):
    pool = await get_pool()
    async with pool.acquire() as conn:
        row = await conn.fetchrow("""
            INSERT INTO views (slug, count, last_seen)
            VALUES ($1, 1, now())
            ON CONFLICT (slug) DO UPDATE
            SET count     = views.count + 1,
                last_seen = now()
            RETURNING count
        """, slug)
    return {"slug": slug, "count": row["count"]}

The {slug:path} parameter type tells FastAPI to accept forward slashes in the slug — necessary because Hugo post URLs include the full path like posts/my-post-title/.

src/view_counter/app.py:

from contextlib import asynccontextmanager
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from .database import init_db, close_pool
from .routes import router


@asynccontextmanager
async def lifespan(app: FastAPI):
    await init_db()
    yield
    await close_pool()


def create_app() -> FastAPI:
    app = FastAPI(
        title="View Counter",
        version="0.1.0",
        lifespan=lifespan,
    )

    app.add_middleware(
        CORSMiddleware,
        allow_origins=[
            "https://uclab.dev",
            "http://localhost:1313",
        ],
        allow_methods=["GET", "POST"],
        allow_headers=["*"],
    )

    app.include_router(router)
    return app

main.py:

import uvicorn
from src.view_counter.app import create_app

app = create_app()

if __name__ == "__main__":
    uvicorn.run(
        "main:app",
        host="0.0.0.0",
        port=9313,
        reload=True,
    )

Dockerfile

Multi-stage build using the official uv image as builder. The final image runs as a non-root user with a read-only root filesystem.

FROM python:3.12-slim AS builder

COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv

WORKDIR /app

COPY pyproject.toml uv.lock ./
RUN uv sync --frozen --no-dev --no-cache

COPY src/ ./src/
COPY main.py ./

FROM python:3.12-slim

RUN useradd --no-create-home --shell /bin/false appuser

WORKDIR /app

COPY --from=builder /app ./
COPY --from=builder /app/.venv ./.venv

ENV PATH="/app/.venv/bin:$PATH"
ENV PYTHONUNBUFFERED=1

USER appuser

EXPOSE 9313

CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "9313"]

Key decisions:

uv resolves dependencies deterministically from uv.lock
--frozen ensures the lockfile is always honoured in CI
--no-dev excludes test dependencies from the production image
Non-root appuser satisfies the cluster pod security policy
readOnlyRootFilesystem: true enforced at the Kubernetes level

Forgejo CI Pipeline

The pipeline builds the image, signs it with Cosign, and updates the image digest in the GitOps repo to trigger a Flux reconciliation.

.forgejo/workflows/build.yml:

name: Build and Deploy
on:
  push:
    branches: [main]

env:
  REGISTRY: forgejo.uclab.dev
  IMAGE: forgejo.uclab.dev/affragak/view-counter

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Repo
        uses: actions/checkout@v4
        with:
          submodules: recursive
          fetch-depth: 0

      - name: Set image tag
        run: |
          SHORT_SHA=$(git rev-parse --short HEAD)
          echo "TAG=${SHORT_SHA}" >> $GITHUB_ENV

      - name: Login to Forgejo registry
        run: echo "${{ secrets.REGISTRY_TOKEN }}" | docker login ${{ env.REGISTRY }} -u ${{ secrets.REGISTRY_USER }} --password-stdin

      - name: Build and push image
        run: |
          docker build -t ${{ env.IMAGE }}:${{ env.TAG }} .
          docker push ${{ env.IMAGE }}:${{ env.TAG }}
          DIGEST=$(docker inspect --format='{{index .RepoDigests 0}}' ${{ env.IMAGE }}:${{ env.TAG }})
          echo "IMAGE_WITH_DIGEST=${DIGEST}" >> $GITHUB_ENV

      - name: Install Cosign
        uses: sigstore/[email protected]

      - name: Sign image with Cosign
        env:
          COSIGN_PASSWORD: ${{ secrets.COSIGN_PASSWORD }}
        run: |
          echo "${{ secrets.COSIGN_PRIVATE_KEY }}" > /tmp/cosign.key
          cosign sign --yes --key /tmp/cosign.key \
            --registry-referrers-mode=legacy \
            --registry-username ${{ secrets.REGISTRY_USER }} \
            --registry-password ${{ secrets.REGISTRY_TOKEN }} \
            ${{ env.IMAGE_WITH_DIGEST }}
          rm /tmp/cosign.key

      - name: Setup SSH for GitHub
        run: |
          mkdir -p ~/.ssh
          echo "${{ secrets.GH_DEPLOY_KEY }}" > ~/.ssh/id_ed25519
          chmod 600 ~/.ssh/id_ed25519
          ssh-keyscan github.com >> ~/.ssh/known_hosts

      - name: Clone k3s repo and update image tag
        run: |
          git clone [email protected]:affragak/pi5cluster.git /tmp/pi5cluster
          cd /tmp/pi5cluster
          git config user.name "forgejo-ci"
          git config user.email "[email protected]"
          DEPLOY_FILE="apps/base/view-counter/deployment.yaml"
          sed -i "s|image: .*|image: ${{ env.IMAGE_WITH_DIGEST }}|" $DEPLOY_FILE
          git add $DEPLOY_FILE
          git diff --staged --quiet && echo "No changes to commit" && exit 0
          git commit -m "chore: deploy view-counter ${{ env.TAG }}"
          git push

Required Forgejo repository secrets:

Secret	Purpose
`REGISTRY_USER`	Forgejo registry username
`REGISTRY_TOKEN`	Forgejo token with `write:packages` scope
`COSIGN_PRIVATE_KEY`	Cosign private key stored in Vault
`COSIGN_PASSWORD`	Cosign key password
`GH_DEPLOY_KEY`	SSH deploy key for pi5cluster repo

Kubernetes Manifests

All manifests live in apps/base/view-counter/ in the pi5cluster Flux repo and are reconciled by Flux automatically on every push.

namespace.yaml:

apiVersion: v1
kind: Namespace
metadata:
  name: view-counter

secret.yaml — ExternalSecret synced from Vault via External Secrets Operator:

apiVersion: external-secrets.io/v1
kind: ExternalSecret
metadata:
  name: view-counter-container-env
  namespace: view-counter
spec:
  refreshInterval: "15s"
  secretStoreRef:
    name: vault-backend-global
    kind: ClusterSecretStore
  target:
    name: view-counter-container-env
    creationPolicy: Owner
  data:
    - secretKey: DB_USER
      remoteRef:
        key: view-counter-container-env
        property: username
    - secretKey: DB_PASSWORD
      remoteRef:
        key: view-counter-container-env
        property: password

Store credentials in Vault before deploying:

vault kv put -mount=apps view-counter-container-env \
  username=view-counter \
  password=$(openssl rand -base64 24)

configmap.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: viewcounter-configmap
data:
  DB_NAME: view-counter
  DB_PORT: "5432"
  DB_HOST: view-counter-db-rw.view-counter.svc.cluster.local

database.yaml — CNPG Cluster with two instances and WAL archiving:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: view-counter-db
  namespace: view-counter
spec:
  instances: 2
  bootstrap:
    initdb:
      database: view-counter
      owner: view-counter
      secret:
        name: view-counter-container-env
  storage:
    size: 1Gi
  monitoring:
    enablePodMonitor: true

deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: view-counter
  namespace: view-counter
spec:
  replicas: 1
  selector:
    matchLabels:
      app: view-counter
  template:
    metadata:
      labels:
        app: view-counter
    spec:
      automountServiceAccountToken: false
      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        runAsGroup: 1000
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: view-counter
          image: forgejo.uclab.dev/affragak/view-counter:placeholder
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop: [ALL]
          ports:
            - containerPort: 9313
          envFrom:
            - configMapRef:
                name: viewcounter-configmap
            - secretRef:
                name: view-counter-container-env
          resources:
            requests:
              cpu: 20m
              memory: 64Mi
            limits:
              cpu: 200m
              memory: 128Mi
          livenessProbe:
            httpGet:
              path: /health
              port: 9313
            initialDelaySeconds: 10
            periodSeconds: 30
          readinessProbe:
            httpGet:
              path: /health
              port: 9313
            initialDelaySeconds: 5
            periodSeconds: 10
      imagePullSecrets:
        - name: forgejo-registry

service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: viewcounter-server
  namespace: view-counter
spec:
  selector:
    app: view-counter
  ports:
    - port: 9313
      targetPort: 9313
  type: ClusterIP

kustomization.yaml:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - namespace.yaml
  - secret.yaml
  - configmap.yaml
  - database.yaml
  - deployment.yaml
  - service.yaml

Cloudflare Tunnel

The service has no public port. Traffic reaches it exclusively through the Cloudflare Tunnel. Add the route to the cloudflared ConfigMap in the Flux repo:

ingress:
  - hostname: viewcounter.uclab.dev
    service: http://viewcounter-server.view-counter.svc.cluster.local:9313

Add a CNAME DNS record in Cloudflare pointing viewcounter to your tunnel’s .cfargotunnel.com address. Restart cloudflared:

kubectl rollout restart deployment cloudflared -n cloudflared
curl -s https://viewcounter.uclab.dev/health
# {"status":"ok"}

Hugo Integration

Reading time comes from Hugo’s native .ReadingTime — zero extra infrastructure. The view counter is a small JavaScript snippet that calls the API on every post load.

Add to config.toml:

[params]
  viewCounterHost = "https://viewcounter.uclab.dev"

Add to the aside block in layouts/_default/single.html, above the date:

<p>
    <span>{{ .ReadingTime }} min read</span>
    &nbsp;·&nbsp;
    <span id="view-count"></span>
</p>

<script>
(async () => {
    const slug = '{{ .RelPermalink }}'.replace(/^\//, '');
    const base = '{{ .Site.Params.viewCounterHost }}';
    try {
        await fetch(base + '/views/' + slug, { method: 'POST' });
        const res = await fetch(base + '/views/' + slug);
        const data = await res.json();
        document.getElementById('view-count').textContent = data.count + ' views';
    } catch(e) {
        document.getElementById('view-count').textContent = '';
    }
})();
</script>

The script POSTs to increment then GETs to display. The try/catch silently hides any failure — a microservice hiccup never affects the reading experience. The leading slash is stripped from .RelPermalink since FastAPI’s {slug:path} parameter handles the remaining segments.

Verification

# Health check
curl https://viewcounter.uclab.dev/health
# {"status":"ok"}

# Increment a counter
curl -X POST "https://viewcounter.uclab.dev/views/posts/my-post/"
# {"slug":"posts/my-post/","count":1}

# Read a counter
curl "https://viewcounter.uclab.dev/views/posts/my-post/"
# {"slug":"posts/my-post/","count":1}

# All counters ranked by views
curl "https://viewcounter.uclab.dev/views"
# [{"slug":"posts/my-post/","count":1}]

# Database cluster health
kubectl cnpg status view-counter-db -n view-counter

What This Demonstrates

This project covers the full DevOps lifecycle for a greenfield microservice:

Code — Python FastAPI structured as a proper package with uv for dependency management. Async database access via asyncpg with connection pooling. CORS configured for the exact origins that need access. Graceful startup without a database connection so the container passes readiness probes even before the CNPG cluster is ready.

Container — Multi-stage Dockerfile with uv as the build tool. Final image is 50MB, runs as non-root with a read-only root filesystem. The CI runner builds natively for the target architecture.

Supply chain — Every image is signed with Cosign before being pushed. The signing key lives in Vault and is injected into the CI runner’s ephemeral /tmp for the duration of the signing step then deleted. The ClusterImagePolicy enforces signature verification at admission time for namespaces that carry the policy.sigstore.dev/include: "true" label.

GitOps — The CI pipeline never deploys directly to the cluster. It updates the image digest in the pi5cluster repo and Flux reconciles the change on its next sync cycle. The cluster state is always the source of truth in Git. A rolling update replaces the old pod only after the new one passes its readiness probe.

Database — PostgreSQL managed by CloudNative-PG with two instances, streaming replication across two NUC nodes, and WAL archiving to MinIO for point-in-time recovery. The schema is created at application startup via asyncpg — no migration tooling needed for a single table.

Secrets — Credentials stored in Vault, synced into the cluster via External Secrets Operator with a 15 second refresh interval. The ExternalSecret manifest is safe to commit to Git — it contains only a reference to the Vault path, never the value.

Networking — ClusterIP service, no NodePort or LoadBalancer. The only ingress path is through the Cloudflare Tunnel which terminates TLS and enforces zero-trust access policies before traffic reaches the pod.

Observability — CNPG enablePodMonitor: true wires Prometheus scraping automatically. Liveness and readiness probes on /health give Kubernetes accurate signal for traffic routing and restart decisions.

my DevOps Odyssey

“Σα βγεις στον πηγαιμό για την Ιθάκη, να εύχεσαι να ‘ναι μακρύς ο δρόμος, γεμάτος περιπέτειες, γεμάτος γνώσεις.” - Kavafis’ Ithaka.

Building a View Counter Microservice for my Hugo Blog on k3s

9 min read · · views

2026-03-19

Series:lab

Categories:devops

Tags:#k3s, #hugo, #python, #devops, #lab

Building a Microservice for my Hugo Blog on k3s: