Add self-standing dockercoins intro for admin course

slides/k8s/kubercoins.md

@@ -0,0 +1,244 @@
+# Deploying a sample application
+
+- We will connect to our new Kubernetes cluster
+
+- We will deploy a sample application, "DockerCoins"
+
+- That app features multiple micro-services and a web UI
+
+---
+
+## Connecting to our Kubernetes cluster
+
+- Our cluster has multiple nodes named `node1`, `node2`, etc.
+
+- We will do everything from `node1`
+
+- We have SSH access to the other nodes, but won't need it
+
+  (but we can use it for debugging, troubleshooting, etc.)
+
+.exercise[
+
+- Log into `node1`
+
+- Check that all nodes are `Ready`:
+  ```bash
+  kubectl get nodes
+  ```
+
+]
+
+---
+
+## Cloning some repos
+
+- We will need two repositories:
+
+  - the first one has the "DockerCoins" demo app
+
+  - the second one has these slides, some scripts, more manifests ...
+
+.exercise[
+
+- Clone the kubercoins repository on `node1`:
+  ```bash
+  git clone https://github.com/jpetazzo/kubercoins
+  ```
+
+
+- Clone the container.training repository as well:
+  ```bash
+  git clone https://@@GITREPO@@
+  ```
+
+]
+
+---
+
+## Running the application
+
+Without further ado, let's start this application!
+
+.exercise[
+
+- Apply all the manifests from the kubercoins repository:
+  ```bash
+  kubectl apply -f kubercoins/
+  ```
+
+]
+
+---
+
+## What's this application?
+
+--
+
+- It is a DockerCoin miner! .emoji[💰🐳📦🚢]
+
+--
+
+- No, you can't buy coffee with DockerCoins
+
+--
+
+- How DockerCoins works:
+
+  - generate a few random bytes
+
+  - hash these bytes
+
+  - increment a counter (to keep track of speed)
+
+  - repeat forever!
+
+--
+
+- DockerCoins is *not* a cryptocurrency
+
+  (the only common points are "randomness", "hashing", and "coins" in the name)
+
+---
+
+## DockerCoins in the microservices era
+
+- DockerCoins is made of 5 services:
+
+  - `rng` = web service generating random bytes
+
+  - `hasher` = web service computing hash of POSTed data
+
+  - `worker` = background process calling `rng` and `hasher`
+
+  - `webui` = web interface to watch progress
+
+  - `redis` = data store (holds a counter updated by `worker`)
+
+- These 5 services are visible in the application's Compose file,
+  [docker-compose.yml](
+  https://@@GITREPO@@/blob/master/dockercoins/docker-compose.yml)
+
+---
+
+## How DockerCoins works
+
+- `worker` invokes web service `rng` to generate random bytes
+
+- `worker` invokes web service `hasher` to hash these bytes
+
+- `worker` does this in an infinite loop
+
+- every second, `worker` updates `redis` to indicate how many loops were done
+
+- `webui` queries `redis`, and computes and exposes "hashing speed" in our browser
+
+*(See diagram on next slide!)*
+
+---
+
+class: pic
+
+![Diagram showing the 5 containers of the applications](images/dockercoins-diagram.svg)
+
+---
+
+## Service discovery in container-land
+
+How does each service find out the address of the other ones?
+
+--
+
+- We do not hard-code IP addresses in the code
+
+- We do not hard-code FQDNs in the code, either
+
+- We just connect to a service name, and container-magic does the rest
+
+  (And by container-magic, we mean "a crafty, dynamic, embedded DNS server")
+
+---
+
+## Example in `worker/worker.py`
+
+```python
+redis = Redis("`redis`")
+
+
+def get_random_bytes():
+    r = requests.get("http://`rng`/32")
+    return r.content
+
+
+def hash_bytes(data):
+    r = requests.post("http://`hasher`/",
+                      data=data,
+                      headers={"Content-Type": "application/octet-stream"})
+```
+
+(Full source code available [here](
+https://@@GITREPO@@/blob/8279a3bce9398f7c1a53bdd95187c53eda4e6435/dockercoins/worker/worker.py#L17
+))
+
+---
+
+## Show me the code!
+
+- You can check the GitHub repository with all the materials of this workshop:
+  <br/>https://@@GITREPO@@
+
+- The application is in the [dockercoins](
+  https://@@GITREPO@@/tree/master/dockercoins)
+  subdirectory
+
+- The Compose file ([docker-compose.yml](
+  https://@@GITREPO@@/blob/master/dockercoins/docker-compose.yml))
+  lists all 5 services
+
+- `redis` is using an official image from the Docker Hub
+
+- `hasher`, `rng`, `worker`, `webui` are each built from a Dockerfile
+
+- Each service's Dockerfile and source code is in its own directory
+
+  (`hasher` is in the [hasher](https://@@GITREPO@@/blob/master/dockercoins/hasher/) directory,
+  `rng` is in the [rng](https://@@GITREPO@@/blob/master/dockercoins/rng/)
+  directory, etc.)
+
+---
+
+## Our application at work
+
+- We can check the logs our application pods
+
+.exercise[
+
+- Check the logs of the various components:
+  ```bash
+  kubectl logs deploy/worker
+  kubectl logs deploy/hasher
+  ```
+
+]
+
+---
+
+## Connecting to the web UI
+
+- "Logs are exciting and fun!" (No-one, ever)
+
+- The `webui` container exposes a web dashboard; let's view it
+
+.exercise[
+
+- Check the NodePort allocated to the web UI:
+  ```bash
+  kubectl get svc webui
+  ```
+
+- Open that in a web browser
+
+]
+
+A drawing area should show up, and after a few seconds, a blue
+graph will appear.