# Which application needs to be secured

- It is a DockerCoin miner! 💰🐳📦🚢

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- No, you can't buy coffee with DockerCoin

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- How dockercoins works:

  - generate a few random bytes

  - hash these bytes

  - increment a counter (to keep track of speed)

  - repeat forever!

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- DockerCoin is *not* a cryptocurrency

  (the only common points are "randomness," "hashing," and "coins" in the name)

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## DockerCoin in the microservices era

- The dockercoins app 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://github.com/jpetazzo/container.training/blob/main/dockercoins/docker-compose.yml)

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## 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!)*

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class: pic

![Diagram showing the 5 containers of the applications](images/dockercoins-diagram.png)