blog/content/posts/20-build-your-own-kubernetes-cluster-part-11/index.md

---
title: "Setup a HA Kubernetes cluster Part XI - Load testing & Frontend"
date: 2023-10-10
description: "Follow this opinionated guide as starter-kit for your own Kubernetes platform..."
tags: ["kubernetes", "testing", "sonarqube", "load-testing", "k6"]
draft: true
---

{{< lead >}}
Be free from AWS/Azure/GCP by building a production grade On-Premise Kubernetes cluster on cheap VPS provider, fully GitOps managed, and with complete CI/CD tools 🎉
{{< /lead >}}

This is the **Part X** of more global topic tutorial. [Back to first part]({{< ref "/posts/10-build-your-own-kubernetes-cluster" >}}) for intro.

## Load testing

When it comes load testing, k6 is a perfect tool for this job and integrate with many real time series database integration like Prometheus or InfluxDB. As we already have Prometheus, let's use it and avoid us a separate InfluxDB installation. First be sure to allow remote write by enable `enableRemoteWriteReceiver` in the Prometheus Helm chart. It should be already done if you follow this tutorial.

### K6

We'll reuse our flux repo and add some manifests for defining the load testing scenario. Firstly describe the scenario inside `ConfigMap` that scrape all articles and then each article:

{{< highlight host="demo-kube-flux" file="jobs/demo-k6.yaml" >}}

```yml
apiVersion: v1
kind: ConfigMap
metadata:
  name: scenario
  namespace: kuberocks
data:
  script.js: |
    import http from "k6/http";
    import { check } from "k6";

    export default function () {
      const size = 10;
      let page = 1;

      let articles = []

      do {
        const res = http.get(`${__ENV.API_URL}/Articles?page=${page}&size=${size}`);
        check(res, {
          "status is 200": (r) => r.status == 200,
        });

        articles = res.json().articles;
        page++;

        articles.forEach((article) => {
          const res = http.get(`${__ENV.API_URL}/Articles/${article.slug}`);
          check(res, {
            "status is 200": (r) => r.status == 200,
          });
        });
      }
      while (articles.length > 0);
    }
```

{{< /highlight >}}

And add the k6 `Job` in the same file and configure it for Prometheus usage and mounting above scenario:

{{< highlight host="demo-kube-flux" file="jobs/demo-k6.yaml" >}}

```yml
#...
---
apiVersion: batch/v1
kind: Job
metadata:
  name: k6
  namespace: kuberocks
spec:
  ttlSecondsAfterFinished: 0
  template:
    spec:
      restartPolicy: Never
      containers:
        - name: run
          image: grafana/k6
          env:
            - name: API_URL
              value: https://demo.kube.rocks/api
            - name: K6_VUS
              value: "30"
            - name: K6_DURATION
              value: 1m
            - name: K6_PROMETHEUS_RW_SERVER_URL
              value: http://prometheus-operated.monitoring:9090/api/v1/write
          command:
            ["k6", "run", "-o", "experimental-prometheus-rw", "script.js"]
          volumeMounts:
            - name: scenario
              mountPath: /home/k6
      tolerations:
        - key: node-role.kubernetes.io/runner
          operator: Exists
          effect: NoSchedule
      nodeSelector:
        node-role.kubernetes.io/runner: "true"
      volumes:
        - name: scenario
          configMap:
            name: scenario
```

{{< /highlight >}}

Use appropriate `tolerations` and `nodeSelector` for running the load testing in a node which have free CPU resource. You can play with `K6_VUS` and `K6_DURATION` environment variables in order to change the level of load testing.

Then you can launch the job with `ka jobs/demo-k6.yaml`. Check quickly that the job is running via `klo -n kuberocks job/k6`:

```txt

        /\      |‾‾| /‾‾/   /‾‾/
   /\  /  \     |  |/  /   /  /
  /  \/    \    |     (   /   ‾‾\
 /          \   |  |\  \ |  (‾)  |
/ __________ \  |__| \__\ \_____/ .io

execution: local
   script: script.js
   output: Prometheus remote write (http://prometheus-operated.monitoring:9090/api/v1/write)

scenarios: (100.00%) 1 scenario, 30 max VUs, 1m30s max duration (incl. graceful stop):
         * default: 30 looping VUs for 1m0s (gracefulStop: 30s)
```

After 1 minute of run, job should finish and show some raw result:

```txt
✓ status is 200

checks.........................: 100.00% ✓ 17748     ✗ 0
data_received..................: 404 MB  6.3 MB/s
data_sent......................: 1.7 MB  26 kB/s
http_req_blocked...............: avg=242.43µs min=223ns   med=728ns   max=191.27ms p(90)=1.39µs   p(95)=1.62µs
http_req_connecting............: avg=13.13µs  min=0s      med=0s      max=9.48ms   p(90)=0s       p(95)=0s
http_req_duration..............: avg=104.22ms min=28.9ms  med=93.45ms max=609.86ms p(90)=162.04ms p(95)=198.93ms
  { expected_response:true }...: avg=104.22ms min=28.9ms  med=93.45ms max=609.86ms p(90)=162.04ms p(95)=198.93ms
http_req_failed................: 0.00%   ✓ 0         ✗ 17748
http_req_receiving.............: avg=13.76ms  min=32.71µs med=6.49ms  max=353.13ms p(90)=36.04ms  p(95)=51.36ms
http_req_sending...............: avg=230.04µs min=29.79µs med=93.16µs max=25.75ms  p(90)=201.92µs p(95)=353.61µs
http_req_tls_handshaking.......: avg=200.57µs min=0s      med=0s      max=166.91ms p(90)=0s       p(95)=0s
http_req_waiting...............: avg=90.22ms  min=14.91ms med=80.76ms max=609.39ms p(90)=138.3ms  p(95)=169.24ms
http_reqs......................: 17748   276.81409/s
iteration_duration.............: avg=5.39s    min=3.97s   med=5.35s   max=7.44s    p(90)=5.94s    p(95)=6.84s
iterations.....................: 348     5.427727/s
vus............................: 7       min=7       max=30
vus_max........................: 30      min=30      max=30
```

As we use Prometheus for outputting the result, we can visualize it easily with Grafana. You just have to import [this dashboard](https://grafana.com/grafana/dashboards/18030-official-k6-test-result/):

[![Grafana](grafana-k6.png)](grafana-k6.png)

As we use Kubernetes, increase the loading performance horizontally is dead easy. Go to the deployment configuration of demo app for increasing replicas count, as well as Traefik, and compare the results.

### Load balancing database

So far, we only load balanced the stateless API, but what about the database part ? We have set up a replicated PostgreSQL cluster, however we have no use of the replica that stay sadly idle. But for that we have to distinguish write queries from scalable read queries.

We can make use of the Bitnami [PostgreSQL HA](https://artifacthub.io/packages/helm/bitnami/postgresql-ha) instead of simple one. It adds the new component [Pgpool-II](https://pgpool.net/mediawiki/index.php/Main_Page) as main load balancer and detect failover. It's able to separate in real time write queries from read queries and send them to the master or the replica. The advantage: works natively for all apps without any changes. The cons: it consumes far more resources and add a new component to maintain.

A 2nd solution is to separate query typologies from where it counts: the application. It requires some code changes, but it's clearly a far more efficient solution. Let's do this way.

As Npgsql support load balancing [natively](https://www.npgsql.org/doc/failover-and-load-balancing.html), we don't need to add any Kubernetes service. We just have to create a clear distinction between read and write queries. One simple way is to create a separate RO `DbContext`.

{{< highlight host="kuberocks-demo" file="src/KubeRocks.Application/Contexts/AppRoDbContext.cs" >}}

```cs
namespace KubeRocks.Application.Contexts;

using KubeRocks.Application.Entities;

using Microsoft.EntityFrameworkCore;

public class AppRoDbContext : DbContext
{
    public DbSet<User> Users => Set<User>();
    public DbSet<Article> Articles => Set<Article>();
    public DbSet<Comment> Comments => Set<Comment>();

    public AppRoDbContext(DbContextOptions<AppRoDbContext> options) : base(options)
    {
    }
}
```

{{< /highlight >}}

Register it in DI:

{{< highlight host="kuberocks-demo" file="src/KubeRocks.Application/Extensions/ServiceExtensions.cs" >}}

```cs
public static class ServiceExtensions
{
    public static IServiceCollection AddKubeRocksServices(this IServiceCollection services, IConfiguration configuration)
    {
        return services
            //...
            .AddDbContext<AppRoDbContext>((options) =>
            {
                options.UseNpgsql(
                    configuration.GetConnectionString("DefaultRoConnection")
                    ??
                    configuration.GetConnectionString("DefaultConnection")
                );
            });
    }
}
```

{{< /highlight >}}

We fall back to the RW connection string if the RO one is not defined. Then use it in the `ArticlesController` which as only read endpoints:

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/Controllers/ArticlesController.cs" >}}

```cs
//...

public class ArticlesController
{
    private readonly AppRoDbContext _context;

    //...

    public ArticlesController(AppRoDbContext context)
    {
        _context = context;
    }

    //...
}
```

{{< /highlight >}}

Push and let it pass the CI. In the meantime, add the new RO connection:

{{< highlight host="demo-kube-flux" file="clusters/demo/kuberocks/deploy-demo.yaml" >}}

```yaml
# ...
spec:
  # ...
  template:
    # ...
    spec:
      # ...
      containers:
        - name: api
          # ...
          env:
            - name: DB_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: demo-db
                  key: password
            - name: ConnectionStrings__DefaultConnection
              value: Host=postgresql-primary.postgres;Username=demo;Password='$(DB_PASSWORD)';Database=demo;
            - name: ConnectionStrings__DefaultRoConnection
              value: Host=postgresql-primary.postgres,postgresql-read.postgres;Username=demo;Password='$(DB_PASSWORD)';Database=demo;Load Balance Hosts=true;
#...
```

{{< /highlight >}}

We simply have to add multiple host like `postgresql-primary.postgres,postgresql-read.postgres` for the RO connection string and enable LB mode with `Load Balance Hosts=true`.

Once deployed, relaunch a load test with K6 and admire the DB load balancing in action on both storage servers with `htop` or directly compute pods by namespace in Grafana.

[![Gafana DB load balancing](grafana-db-lb.png)](grafana-db-lb.png)

## Frontend

Let's finish this guide by a quick view of SPA frontend development as a separate project from backend.

### Vue TS

Create a new Vue.js project from [vitesse starter kit](https://github.com/antfu/vitesse-lite) (be sure to have pnpm, just a matter of `scoop/brew install pnpm`):

```sh
npx degit antfu/vitesse-lite kuberocks-demo-ui
cd kuberocks-demo-ui
git init
git add .
git commit -m "Initial commit"
pnpm i
pnpm dev
```

Should launch app in `http://localhost:3333/`. Create a new `kuberocks-demo-ui` Gitea repo and push this code into it. Now lets quick and done for API calls.

### Get around CORS and HTTPS with YARP

As always when frontend is separated from backend, we have to deal with CORS. But I prefer to have one single URL for frontend + backend and get rid of CORS problem by simply call under `/api` path. Moreover, it'll be production ready without need to manage any `Vite` variable for API URL and we'll get HTTPS provided by dotnet. Back to API project.

For convenience, let's change the randomly generated ASP.NET ports by predefined ones:

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/Properties/launchSettings.json" >}}

```json
{
  //...
  "profiles": {
    "http": {
      //...
      "applicationUrl": "http://localhost:5000",
      //...
    },
    "https": {
      //...
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      //...
    },
    //...
  }
}
```

{{< /highlight >}}

```sh
dotnet add src/KubeRocks.WebApi package Yarp.ReverseProxy
```

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/Program.cs" >}}

```cs
//...

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddReverseProxy()
    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));

//...

var app = builder.Build();

app.MapReverseProxy();

//...

app.UseRouting();

//...
```

{{< /highlight >}}

Note as we must add `app.UseRouting();` too in order to get Swagger UI working.

The proxy configuration (only for development):

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/appsettings.Development.json" >}}

```json
{
  //...
  "ReverseProxy": {
    "Routes": {
      "ServerRouteApi": {
        "ClusterId": "Server",
        "Match": {
          "Path": "/api/{**catch-all}"
        },
        "Transforms": [
          {
            "PathRemovePrefix": "/api"
          }
        ]
      },
      "ClientRoute": {
        "ClusterId": "Client",
        "Match": {
          "Path": "{**catch-all}"
        }
      }
    },
    "Clusters": {
      "Client": {
        "Destinations": {
          "Client1": {
            "Address": "http://localhost:3333"
          }
        }
      },
      "Server": {
        "Destinations": {
          "Server1": {
            "Address": "https://localhost:5001"
          }
        }
      }
    }
  }
}
```

{{< /highlight >}}

Now your frontend app should appear under `https://localhost:5001`, and API calls under `https://localhost:5001/api`. We now benefit from HTTPS for all app. Push API code.

### Typescript API generator

As we use OpenAPI, it's possible to generate typescript client for API calls. Add this package:

```sh
pnpm add openapi-typescript -D
pnpm add openapi-typescript-fetch
```

Before generate the client model, go back to backend for forcing required by default for attributes when not nullable when using `Swashbuckle.AspNetCore`:

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/Filters/RequiredNotNullableSchemaFilter.cs" >}}

```cs
using Microsoft.OpenApi.Models;

using Swashbuckle.AspNetCore.SwaggerGen;

namespace KubeRocks.WebApi.Filters;

public class RequiredNotNullableSchemaFilter : ISchemaFilter
{
    public void Apply(OpenApiSchema schema, SchemaFilterContext context)
    {
        if (schema.Properties is null)
        {
            return;
        }

        var notNullableProperties = schema
            .Properties
            .Where(x => !x.Value.Nullable && !schema.Required.Contains(x.Key))
            .ToList();

        foreach (var property in notNullableProperties)
        {
            schema.Required.Add(property.Key);
        }
    }
}
```

{{< /highlight >}}

{{< highlight host="kuberocks-demo" file="src/KubeRocks.WebApi/Program.cs" >}}

```cs
//...

builder.Services.AddSwaggerGen(o =>
{
    o.SupportNonNullableReferenceTypes();
    o.SchemaFilter<RequiredNotNullableSchemaFilter>();
});

//...
```

{{< /highlight >}}

You should now have proper required attributes for models in swagger UI:

[![Frontend](swagger-ui-nullable.png)](swagger-ui-nullable.png)

{{< alert >}}
Sadly, without this boring step, many attributes will be nullable when generating TypeScript models, and leads to headaches from client side by forcing us to manage nullable everywhere.
{{< /alert >}}

Now generate the models:

{{< highlight host="kuberocks-demo-ui" file="package.json" >}}

```json
{
  //...
  "scripts": {
    //...
    "openapi": "openapi-typescript http://localhost:5000/api/v1/swagger.json --output src/api/openapi.ts"
  },
  //...
}
```

{{< /highlight >}}

Use the HTTP version of swagger as you'll get a self certificate error. The use `pnpm openapi` to generate full TS model. Finally, describe API fetchers like so:

{{< highlight host="kuberocks-demo-ui" file="src/api/index.ts" >}}

```ts
import { Fetcher } from 'openapi-typescript-fetch'

import type { components, paths } from './openapi'

const fetcher = Fetcher.for<paths>()

type ArticleList = components['schemas']['ArticleListDto']
type Article = components['schemas']['ArticleDto']

const getArticles = fetcher.path('/api/Articles').method('get').create()
const getArticleBySlug = fetcher.path('/api/Articles/{slug}').method('get').create()

export type { Article, ArticleList }
export {
  getArticles,
  getArticleBySlug,
}
```

{{< /highlight >}}

We are now fully typed compliant with the API.

### Call the API

Let's create a pretty basic list + detail vue pages:

{{< highlight host="kuberocks-demo-ui" file="src/pages/articles/index.vue" >}}

```vue
<script lang="ts" setup>
import { getArticles } from '~/api'
import type { ArticleList } from '~/api'

const articles = ref<ArticleList[]>([])

async function loadArticles() {
  const { data } = await getArticles({
    page: 1,
    size: 10,
  })

  articles.value = data.articles
}

loadArticles()
</script>

<template>
  <RouterLink
    v-for="(article, i) in articles"
    :key="i"
    :to="`/articles/${article.slug}`"
  >
    <h3>{{ article.title }}</h3>
  </RouterLink>
</template>
```

{{< /highlight >}}

{{< highlight host="kuberocks-demo-ui" file="src/pages/articles/[slug].vue" >}}

```vue
<script lang="ts" setup>
import { getArticleBySlug } from '~/api'
import type { Article } from '~/api'

const props = defineProps<{ slug: string }>()

const article = ref<Article>()

const router = useRouter()

async function getArticle() {
  const { data } = await getArticleBySlug({ slug: props.slug })

  article.value = data
}

getArticle()
</script>

<template>
  <div v-if="article">
    <h1>{{ article.title }}</h1>
    <p>{{ article.description }}</p>
    <div>{{ article.body }}</div>
    <div>
      <button m-3 mt-8 text-sm btn @click="router.back()">
        Back
      </button>
    </div>
  </div>
</template>
```

{{< /highlight >}}

It should work flawlessly.

### Frontend CI/CD

The CI frontend is far simpler than backend. Create a new `demo-ui` pipeline:

{{< highlight host="demo-kube-flux" file="pipelines/demo-ui.yaml" >}}

```yml
resources:
  - name: version
    type: semver
    source:
      driver: git
      uri: ((git.url))/kuberocks/demo-ui
      branch: main
      file: version
      username: ((git.username))
      password: ((git.password))
      git_user: ((git.git-user))
      commit_message: ((git.commit-message))
  - name: source-code
    type: git
    icon: coffee
    source:
      uri: ((git.url))/kuberocks/demo-ui
      branch: main
      username: ((git.username))
      password: ((git.password))
  - name: docker-image
    type: registry-image
    icon: docker
    source:
      repository: ((registry.name))/kuberocks/demo-ui
      tag: latest
      username: ((registry.username))
      password: ((registry.password))

jobs:
  - name: build
    plan:
      - get: source-code
        trigger: true

      - task: build-source
        config:
          platform: linux
          image_resource:
            type: registry-image
            source:
              repository: node
              tag: 18-buster
          inputs:
            - name: source-code
              path: .
          outputs:
            - name: dist
              path: dist
          caches:
            - path: .pnpm-store
          run:
            path: /bin/sh
            args:
              - -ec
              - |
                corepack enable
                corepack prepare pnpm@latest-8 --activate
                pnpm config set store-dir .pnpm-store
                pnpm i
                pnpm lint
                pnpm build

      - task: build-image
        privileged: true
        config:
          platform: linux
          image_resource:
            type: registry-image
            source:
              repository: concourse/oci-build-task
          inputs:
            - name: source-code
              path: .
            - name: dist
              path: dist
          outputs:
            - name: image
          run:
            path: build
      - put: version
        params: { bump: patch }
      - put: docker-image
        params:
          additional_tags: version/number
          image: image/image.tar
```

{{< /highlight >}}

{{< highlight host="demo-kube-flux" file="pipelines/demo-ui.yaml" >}}

```tf
#...

jobs:
  - name: configure-pipelines
    plan:
      #...
      - set_pipeline: demo-ui
        file: ci/pipelines/demo-ui.yaml
```

{{< /highlight >}}

Apply it and put this nginx `Dockerfile` on frontend root project:

{{< highlight host="kuberocks-demo-ui" file="Dockerfile" >}}

```Dockerfile
FROM nginx:alpine

COPY docker/nginx.conf /etc/nginx/conf.d/default.conf
COPY dist /usr/share/nginx/html
```

{{< /highlight >}}

After push all CI should build correctly. Then the image policy for auto update:

{{< highlight host="demo-kube-flux" file="clusters/demo/kuberocks/images-demo-ui.yaml" >}}

```yml
apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImageRepository
metadata:
  name: demo-ui
  namespace: flux-system
spec:
  image: gitea.kube.rocks/kuberocks/demo-ui
  interval: 1m0s
  secretRef:
    name: dockerconfigjson
---
apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImagePolicy
metadata:
  name: demo-ui
  namespace: flux-system
spec:
  imageRepositoryRef:
    name: demo-ui
    namespace: flux-system
  policy:
    semver:
      range: 0.0.x
```

{{< /highlight >}}

The deployment:

{{< highlight host="demo-kube-flux" file="clusters/demo/kuberocks/deploy-demo-ui.yaml" >}}

```yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo-ui
  namespace: kuberocks
spec:
  replicas: 2
  selector:
    matchLabels:
      app: demo-ui
  template:
    metadata:
      labels:
        app: demo-ui
    spec:
      imagePullSecrets:
        - name: dockerconfigjson
      containers:
        - name: front
          image: gitea.okami101.io/kuberocks/demo-ui:latest # {"$imagepolicy": "flux-system:image-demo-ui"}
          ports:
            - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: demo-ui
  namespace: kuberocks
spec:
  selector:
    app: demo-ui
  ports:
    - name: http
      port: 80
```

{{< /highlight >}}

After push, the demo UI container should be deployed. The very last step is to add a new route to existing `IngressRoute` for frontend:

{{< highlight host="demo-kube-flux" file="clusters/demo/kuberocks/deploy-demo.yaml" >}}

```yaml
#...
apiVersion: traefik.io/v1alpha1
kind: IngressRoute
#...
spec:
  #...
  routes:
    - match: Host(`demo.kube.rocks`)
      kind: Rule
      services:
        - name: demo-ui
          port: http
    - match: Host(`demo.kube.rocks`) && PathPrefix(`/api`)
      #...
```

{{< /highlight >}}

Go to `https://demo.kube.rocks` to confirm if both app front & back are correctly connected !

[![Frontend](frontend.png)](frontend.png)

## Final check 🎊🏁🎊

Congratulation if you're getting that far !!!

We have made an enough complete tour of Kubernetes cluster building on full GitOps mode.