03-Chaperon.md

Declarative computation

The pinnacle of declarative computation is to set it up in one place and run it in another. It allows for composability and for great separation of concerns. This is a standard funcitonal programming design pattern and you'll see it everywhere, including Phoenix and Ecto.

We'll learn it on example of Chaperon.

> LoadTestScenario.init(%Chaperon.Session{})
{:ok,
 %Chaperon.Session{
   assigned: %{interval: 1000, rate: 15},
   async_tasks: %{},
   cancellation: nil,
   config: %{},
   cookies: [],
   errors: %{},
   id: nil,
   interval_task: nil,
   metrics: %{},
   name: nil,
   parent_id: nil,
   parent_pid: nil,
   results: %{},
   scenario: nil,
   timeout_at: nil
 }}

Run as a test!

Chaperon.run_load_test LoadTest, output: "metrics", format: :json
x = %Chaperon.Action.HTTP{
    body: "",
    callback: nil,
    decode: nil,
    headers: %{"Accept" => "*/*", "User-Agent" => "chaperon"},
    method: :get,
    metrics_url: nil,
    params: %{},
    path: "/"
}
v(1).errors[x] |> length

Test from another node

iex --cookie dangerZone420 --name "[email protected]" -S mix

In Erlang to launch observer:

net_kernel:start(['[email protected]']).
erlang:set_cookie('dangerZone420').
net_adm:ping('[email protected]').
erlang:nodes().
observer:start().