container.training/slides/k8s/demo-apps.md

Our demo apps

• We are going to use a few demo apps for demos and labs

• Let's get acquainted with them before we dive in!

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The color app

• Image name: jpetazzo/color, ghcr.io/jpetazzo/color

• Available for linux/amd64, linux/arm64, linux/arm/v7 platforms

• HTTP server listening on port 80

• Serves a web page with a single line of text

• The background of the page is derived from the hostname

  (e.g. if the hostname is blue-xyz-123, the background is blue)

• The web page is "curl-friendly"

  (it contains \r characters to hide HTML tags and declutter the output)

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The color app in action

• Create a Deployment called blue using image jpetazzo/color

• Expose that Deployment with a Service

• Connect to the Service with a web browser

• Connect to the Service with curl

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Dockercoins

• App with 5 microservices:

  • worker (runs an infinite loop connecting to the other services)

  • rng (web service; generates random numbers)

  • hasher (web service; computes SHA sums)

  • redis (holds a single counter incremented by the worker at each loop)

  • webui (web app; displays a graph showing the rate of increase of the counter)

• Uses a mix of Node, Python, Ruby

• Very simple components (approx. 50 lines of code for the most complicated one)

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class: pic

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Deploying Dockercoins

• Pre-built images available as dockercoins/<component>:v0.1

  (e.g. dockercoins/worker:v0.1)

• Containers "discover" each other through DNS

  (e.g. worker connects to http://hasher/)

• A Kubernetes YAML manifest is available in the repo

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The repository

• When we refer to "the" repository, it means:

  https://github.com/jpetazzo/container.training

• It hosts slides, demo apps, deployment scripts...

• All the sample commands, labs, etc. will assume that it's available in:

  ~/container.training

• Let's clone the repo in our environment!

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Cloning the repo

.lab[

• There is a convenient shortcut to clone the repository:

  git clone https://container.training
  

]

While the repository clones, fork it, star it subscribe and hit the bell!

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Running Dockercoins

• All the Kubernetes manifests are in the k8s subdirectory

• This directory has a dockercoins.yaml manifest

.lab[

• Deploy Dockercoins:

  kubectl apply -f ~/container.training/k8s/dockercoins.yaml
  

]

• The webui is exposed with a NodePort service

• Connect to it (through the NodePort or port-forward)

• Note, it might take a minute for the worker to start

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Details

• If the worker Deployment is scaled up, the graph should go up

• The rng Service is meant to be a bottleneck

  (capping the graph to 10/second until rng is scaled up)

• There is artificial latency in the different services

  (so that the app doesn't consume CPU/RAM/network)

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More colors

• The repository also contains a rainbow.yaml manifest

• It creates three namespaces (blue, green, red)

• In each namespace, there is an instance of the color app

  (we can use that later to do literal blue-green deployment!)