container.training/slides/common/sampleapp.md

Our sample application

• Visit the GitHub repository with all the materials of this workshop:
  https://github.com/jpetazzo/container.training

• The application is in the dockercoins subdirectory

• Let's look at the general layout of the source code:

  there is a Compose file docker-compose.yml ...

  ... and 4 other services, each in its own directory:

  • rng = web service generating random bytes
  • hasher = web service computing hash of POSTed data
  • worker = background process using rng and hasher
  • webui = web interface to watch progress

---

What's this application?

--

• It is a DockerCoin miner! .emoji[💰🐳📦🚢]

--

• No, you can't buy coffee with DockerCoins

--

• How DockerCoins works:

  • worker asks to rng to generate a few random bytes

  • worker feeds these bytes into hasher

  • and repeat forever!

  • every second, worker updates redis to indicate how many loops were done

  • webui queries redis, and computes and exposes "hashing speed" in your browser

---

Getting the application source code

• We will clone the GitHub repository

• The repository also contains scripts and tools that we will use through the workshop

.exercise[

• Clone the repository on node1:

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

]

(You can also fork the repository on GitHub and clone your fork if you prefer that.)

---

Running the application

Without further ado, let's start our application.

.exercise[

• Go to the dockercoins directory, in the cloned repo:

  cd ~/container.training/dockercoins
  

• Use Compose to build and run all containers:

  docker-compose up
  

]

Compose tells Docker to build all container images (pulling the corresponding base images), then starts all containers, and displays aggregated logs.

---

Lots of logs

• The application continuously generates logs

• We can see the worker service making requests to rng and hasher

• Let's put that in the background

.exercise[

• Stop the application by hitting ^C

]

• ^C stops all containers by sending them the TERM signal

• Some containers exit immediately, others take longer
  (because they don't handle SIGTERM and end up being killed after a 10s timeout)

---

Connecting to the web UI

• The webui container exposes a web dashboard; let's view it

.exercise[

• With a web browser, connect to node1 on port 8000

• Remember: the nodeX aliases are valid only on the nodes themselves

• In your browser, you need to enter the IP address of your node

]

A drawing area should show up, and after a few seconds, a blue graph will appear.

---

Clean up

• Before moving on, let's remove those containers

.exercise[

• Tell Compose to remove everything:

  docker-compose down
  

]