Giuliano Silvestro
b9fc4f9cf3
The most load-bearing write workflow — droplet provisioning is the spine
of phase 4a deployment onboarding.
DigitalOcean.Client: create_droplet, get_droplet, list_droplets_by_tag,
destroy_droplet. list_paginated/3 now threads caller-supplied params
(opts[:params]) through pagination so tag-filtered listing works.
Four droplet saga steps:
- CreateDroplet — POST a droplet, tagged arcadia-saga-<saga8> +
managed-by-arcadia-cloud. Idempotency: re-run checks context for
droplet_id, then queries DO by the saga tag, so a crash between POST
and context-save adopts the existing droplet. compensate destroys it.
- WaitDropletActive — polls get_droplet until status "active" (96x5s);
records the public IP. No compensation (waiting has no side effect).
- RegisterDroplet — fetches the droplet, upserts it into cloud_resources
(inventory consistent immediately, not at next 15-min sync) and writes
cloud_provisioned desired-state {size_slug, region, image}. compensate
removes the DB rows (the droplet itself is destroyed by CreateDroplet's
compensate).
- DestroyDroplet — DELETE the droplet + mark its cloud_resources row
deleted. Terminal/irreversible: compensate is a logged noop, per the
saga design destroy-class steps don't roll back.
Provisioning helpers:
- provision_droplet/1 — [CreateDroplet, WaitDropletActive, RegisterDroplet]
- destroy_droplet/2 — [DestroyDroplet]
Live smoke verified end-to-end (full create + destroy on a real
s-1vcpu-512mb-10gb droplet in syd1):
- provision saga completed: droplet 572017320 created, reached active
with public IP, registered into cloud_resources (status=active) +
cloud_provisioned (spec recorded).
- destroy saga completed: cloud_resources row marked deleted; droplet
confirmed 404 on DO afterward. Account back to its original 5
droplets, zero leftover, ~1 cent total cost.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
121 lines
3.3 KiB
Elixir
121 lines
3.3 KiB
Elixir
defmodule ArcadiaCloud.Provisioning.Steps.CreateDroplet do
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@moduledoc """
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Creates a DO droplet.
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Saga inputs:
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droplet_name — required
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droplet_region — required (e.g. "syd1")
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droplet_size — required (e.g. "s-1vcpu-1gb")
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droplet_image — required (e.g. "ubuntu-24-04-x64")
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droplet_tags — optional list of extra tags
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droplet_ssh_keys — optional list of SSH key ids/fingerprints
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Idempotency: every droplet is tagged `arcadia-saga-<saga8>`. On re-run
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the step checks context for `droplet_id`, then queries DO for a droplet
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carrying the saga tag — so a crash between POST and context-save adopts
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the existing droplet instead of creating a second.
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Compensation: destroys the droplet.
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"""
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@behaviour ArcadiaCloud.Provisioning.Step
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alias ArcadiaCloud.DigitalOcean.Client
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alias ArcadiaCloud.Provisioning.SagaState
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@impl true
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def name, do: "create_droplet"
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@impl true
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def execute(state) do
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with {:ok, attrs} <- read_inputs(state) do
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saga_tag = saga_tag(state)
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cond do
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SagaState.get_output(state, :droplet_id) ->
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{:ok, state}
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true ->
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case find_by_saga_tag(saga_tag) do
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{:ok, %{"id" => id}} ->
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{:ok, record(state, id, attrs.name)}
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:not_found ->
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create(state, attrs, saga_tag)
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{:error, reason} ->
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{:error, reason}
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end
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end
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end
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end
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@impl true
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def compensate(state) do
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case SagaState.get_output(state, :droplet_id) do
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nil ->
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:ok
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droplet_id ->
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case Client.destroy_droplet(droplet_id) do
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{:ok, _} -> :ok
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{:error, {:http, 404, _}} -> :ok
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{:error, reason} -> {:error, reason}
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end
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end
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end
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# ---- internals ------------------------------------------------------------
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defp create(state, attrs, saga_tag) do
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body = %{
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name: attrs.name,
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region: attrs.region,
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size: attrs.size,
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image: attrs.image,
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tags: [saga_tag, "managed-by-arcadia-cloud" | attrs.tags],
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ssh_keys: attrs.ssh_keys
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}
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case Client.create_droplet(body) do
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{:ok, %{"id" => id}} -> {:ok, record(state, id, attrs.name)}
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{:error, reason} -> {:error, reason}
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end
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end
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defp record(state, droplet_id, name) do
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state
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|> SagaState.put_output(:droplet_id, droplet_id)
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|> SagaState.put_output(:droplet_name, name)
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end
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defp find_by_saga_tag(tag) do
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case Client.list_droplets_by_tag(tag) do
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{:ok, [droplet | _]} -> {:ok, droplet}
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{:ok, []} -> :not_found
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{:error, reason} -> {:error, reason}
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end
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end
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defp saga_tag(state) do
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"arcadia-saga-" <> (state.saga_id |> to_string() |> String.slice(0, 8))
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end
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defp read_inputs(state) do
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attrs = %{
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name: SagaState.get_input(state, :droplet_name),
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region: SagaState.get_input(state, :droplet_region),
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size: SagaState.get_input(state, :droplet_size),
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image: SagaState.get_input(state, :droplet_image),
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tags: SagaState.get_input(state, :droplet_tags) || [],
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ssh_keys: SagaState.get_input(state, :droplet_ssh_keys) || []
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}
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if attrs.name && attrs.region && attrs.size && attrs.image do
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{:ok, attrs}
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else
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{:error, :missing_droplet_inputs}
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end
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end
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end
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