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