https://www.youtube.com/watch?v=JvBT4XBdoUE

Requires Erlang, Elixir, and node.js, as specified in the .tool-versions file. You can use asdf for that.

load_control folder is a library directly being used by the example_system mix project, which is the demo app.

Building:

cd example_system
mix deps.get &&
pushd assets &&
npm install &&
popd &&
mix compile

Starting for development with live reload (recommended for following with youtube):

iex -S mix phx.server

Then, you can visit the following links:

• http://localhost:4000
• http://localhost:4000/load
• http://localhost:4000/services
• http://localhost:4000/top

Building and starting for production (in the background):

cd example_system
./rebuild.sh
./_build/prod/rel/system/bin/system start

Open the remote console:

./_build/prod/rel/system/bin/system remote_console

Hot upgrade with no downtime:

mix system.upgrade

1. ExampleSystem.Metrics.init/1

• calls LoadControl.subscribe_to_stats/0

2. LoadControl.subscribe_to_stats/0

• is a defdelegate to LoadControl.Stats.subscribe/0

3. LoadControl.Stats.subscribe/0

• stores LoadControl pid to its subscribers list in state
• because this was called via defdelegate, this function is viewed as if a public function of LoadControl

1. ExampleSystemWeb.Load.Dashboard.mount/3

• calls ExampleSystem.Metrics.subscribe/0

2. ExampleSystem.Metrics.subscribe/0

• gets the calling pid (Dashboard LiveView), stores into its list of subscribes in state