Add a sample NodeJs Metric Server client

The sample app is a NodeJs app that requests the metrics every second
and prints that in the console. In the deployment is created
a service account, roles and role binding to allows this application
communicate with the api, this token is stored by default
on `/var/run/secrets/kubernetes.io/serviceaccount/token`,
the application is reading that token and doing the requests
on the endpoint `/apis/metrics.k8s.io/v1beta1/pods` that returns
all pod metrics and log it on console.

Story: 2008457
Task: 41954

Change-Id: Ifd56e6e6ef862515d96d6ca22c2146e382bba78c
Signed-off-by: Rafael Jardim <rafaeljordao.jardim@windriver.com>

centos_stable_docker_images.inc

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+sample-app

readme.md

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+# Metrics Server Armada App 
+
+This Armada App is responsible to deliver the metrics server inside the ISO.
+>Metrics Server is a scalable, efficient source of container resource metrics for Kubernetes built-in autoscaling pipelines.
+
+## Structure
+```
+metrics-server-armada-app
+├── centos_build_layer.cfg
+├── centos_iso_image.inc
+├── centos_pkg_dirs
+├── centos_pkg_dirs_containers
+├── centos_stable_docker_images.inc
+├── readme.md
+├── requirements.txt
+├── sample-app
+│   ├── centos
+│   │   ├── docker
+│   │   │   ├── Dockerfile
+│   │   │   └── src
+│   │   │       ├── package.json
+│   │   │       └── sample-application.js
+│   │   └── sample-app.stable_docker_image
+│   └── readme.md
+├── stx-metrics-server-helm
+│   ├── centos
+│   │   ├── build_srpm.data
+│   │   └── stx-metrics-server-helm.spec
+│   └── stx-metrics-server-helm
+│       ├── files
+│       │   ├── index.yaml
+│       │   ├── metadata.yaml
+│       │   └── repositories.yaml
+│       ├── helm-charts
+│       │   ├── Makefile
+│       │   └── metrics-server
+│       │       ├── Chart.yaml
+│       │       ├── templates
+│       │       │   ├── apiservice.yaml
+│       │       │   ├── clusterrole-aggregated-reader.yaml
+│       │       │   ├── clusterrolebinding-auth-delegator.yaml
+│       │       │   ├── clusterrolebinding.yaml
+│       │       │   ├── clusterrole.yaml
+│       │       │   ├── deployment.yaml
+│       │       │   ├── pdb.yaml
+│       │       │   ├── psp.yaml
+│       │       │   ├── rolebinding.yaml
+│       │       │   ├── serviceaccount.yaml
+│       │       │   └── service.yaml
+│       │       └── values.yaml
+│       └── manifests
+│           └── metrics-server_manifest.yaml
+├── test-requirements.txt
+└── tox.ini
+```
+Important files
+- metrics-server_manifest.yaml - Armada Manifest
+- helm-charts - Metrics Server helm charts
+- stx-metrics-server-helm.spec - Steps to generate
+- centos_iso_image.inc - It inserts the rpm inside the ISO
+- centos_pkg_dirs - Folders to build the pkgs
+- sample-app - Sample app application
+
+## Install
+- Navigate to the path `/usr/local/share/applications/helm/`
+- The `metrics-server-1.0-1.tgz` will be present
+- Run `system application-upload metrics-server-1.0-1.tgz`
+- Run `system application-list` to see if it was uploaded
+- Run `system helm-override-update
+    --reuse-values --set sampleApp.create=true
+    metrics-server metrics-server metrics-server` If you want to deploy the sample app
+- Run `system application-apply metrics-server`
+- Run` system application-list` to see if it was applied
+- Run `kubectl get pods -l app=metrics-server -n metrics-server` to see the pod running
+
+
+
+

sample-app/centos/docker/.dockerignore

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+node_modules
+npm-debug.log
+sample-app.yml

sample-app/centos/docker/Dockerfile

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+FROM node:14.15.5-alpine3.13
+
+WORKDIR /usr/src/app
+
+COPY src/package*.json ./
+
+RUN npm install
+
+COPY src/ .
+
+CMD [ "node", "sample-application.js" ]

sample-app/centos/docker/src/package.json

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+{
+  "name": "src",
+  "version": "1.0.0",
+  "description": "",
+  "main": "sample-application.js",
+  "dependencies": {
+    "node-fetch": "2.6.1"
+  },
+  "devDependencies": {},
+  "scripts": {},
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

sample-app/centos/docker/src/sample-application.js

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+
+/* Copyright (c) 2021 Wind River Systems, Inc.
+
+  SPDX-License-Identifier: Apache-2.0 */
+
+
+const fetch = require('node-fetch');
+const https = require('https');
+const fs = require('fs');
+
+const url = "https://kubernetes.default.svc/apis/metrics.k8s.io/v1beta1/pods"
+
+const httpsAgent = new https.Agent({
+  rejectUnauthorized: false,
+});
+
+if (process.env.TOKEN_PATH) {
+  fs.readFile(process.env.TOKEN_PATH, 'utf8', (err, token) => {
+    if (err) {
+      console.error(`Error reading TOKEN_PATH: ${TOKEN_PATH}`, err)
+      return
+    }
+    if (!token) {
+      console.log("Miss the token, stopping the application!")
+      process.exit(1)
+    }
+    setInterval(async () => {
+      try {
+        console.log(`Using the token ${token}`);
+        const response = await fetch(url, {
+          method: 'GET',
+          headers: { "Authorization": `Bearer ${token}` },
+          agent: httpsAgent
+        });
+
+        const body = await response.text();
+        console.log(body);
+      } catch (error) {
+        console.log(`Error requesting ${url}` + error);
+      }
+    }, 1000)
+  });
+} else {
+  console.error("Missing the TOKEN_PATH variable. Stopping the application");
+  process.exit(1)
+}
+
+
+
+
+
+

sample-app/centos/sample-app.stable_docker_image

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+BUILDER=docker
+LABEL=stx-metrics-server-sample-app

sample-app/readme.md

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+# Sample App
+
+Containerized application that retrieves metrics server data
+
+## How does it work ?
+
+ The sample app is a Nodejs app that requests the metrics every second and prints that in the console. The deployment creates a service account, roles and role binding to allows this application communicate with the api, this token is stored by default on `/var/run/secrets/kubernetes.io/serviceaccount/token`, the application is reading that token and doing the requests on the endpoint `/apis/metrics.k8s.io/v1beta1/pods` that returns all pod metrics and log it on console.
+
+## Structure
+```
+sample-app
+├── centos
+│   ├── docker
+│   │   ├── Dockerfile
+│   │   └── src
+│   │       ├── package.json
+│   │       └── sample-application.js
+│   └── sample-app.stable_docker_image
+└── readme.md
+```
+Important files
+- src - Contains Nodejs application
+- Dockerfile - Application Dockerfile
+
+## Run application
+> Deploy tha sample app using `system helm-override-update --reuse-values 
+--set atribute=value <app name> <chart name> <namespace>` folow the steps below:
+
+- Run  `system helm-override-update --reuse-values 
+--set sampleApp.create=true metrics-server metrics-server metrics-server`
+- Run `system application apply metrics-server` to apply the override
+- Run `kubectl get pods -n metric-server-test-app` to get the name of the pod
+- Run `kubectl logs -n metric-server-test-app pod-name --tail 1 -f` to see the logs and check if the sample application is requesting successfully the metrics server api
+
+## Endpoints
+
+All of the following endpoints are GET endpoints and they are under the base path `/apis/metrics.k8s.io/v1beta1`:
+ - `/nodes` - all node metrics
+- `/nodes/{node}` - metrics for a specified node
+- `/namespaces/{namespace}/pods` - all pod metrics within namespace with support for all-namespaces
+- `/namespaces/{namespace}/pods/{pod}` - metrics for a specified pod
+- `/pods` - all pod metrics of all namespaces
+
+