Track errors in Elixir and Phoenix

• An Elixir project with a supervision tree.
• An Observe key that starts with obs_. Read Get an ingest key.
• Version 0.2.0 of the package. It depends on req, jason and telemetry.

# mix.exs
{:postdeploy_sdk, "~> 0.2"}

Run mix deps.get, then set POSTDEPLOY_API_KEY. POSTDEPLOY_ENVIRONMENT and POSTDEPLOY_RELEASE are optional.

Start PostDeploy before the endpoint. It attaches a logger handler that captures crashes, and it listens for Phoenix error renders. PostDeploy.Plug resets the scope for each request and adds the method, host, path and allow-listed headers.

# lib/my_app/application.ex
children = [
  {PostDeploy, []},
  MyAppWeb.Endpoint
]

# lib/my_app_web/endpoint.ex, first plug
plug PostDeploy.Plug

Pass the stacktrace with the exception. Options given to {PostDeploy, opts} win over config :postdeploy_sdk, config: [...], which wins over environment variables.

PostDeploy.set_user(%{id: "user_789", email: "[email protected]"})
PostDeploy.set_tag("plan", "scale")
PostDeploy.set_context("job", %{"queue" => "mailers"})

try do
  raise ArgumentError, "Mailer template is missing"
rescue
  exception ->
    PostDeploy.capture_exception(exception, stacktrace: __STACKTRACE__)
end

PostDeploy.capture_message("Low disk space", "warning")

1. 1

   Step 1. Run a one-file check with the same key.

   check.exs elixir

   Copy

   Mix.install([{:postdeploy_sdk, "0.2.0"}])
   
   {:ok, _pid} = PostDeploy.start_link(environment: "production", release: "1.0.0")
   
   try do
     raise ArgumentError, "Mailer template is missing"
   rescue
     exception -> PostDeploy.capture_exception(exception, stacktrace: __STACKTRACE__)
   end
   
   PostDeploy.flush()
   

2. 2

   Step 2. Run it with POSTDEPLOY_API_KEY=obs_your_key elixir check.exs.

3. 3

   Step 3. Open Observe. The table shows "ArgumentError: Mailer template is missing" with its source and environment.

A crash in a plug is not captured

The logger handler captures crashes, not the plug. Start {PostDeploy, []} in the supervision tree before the endpoint.

Request parameters are missing

The plug does not attach parameters. Add filtered values with PostDeploy.set_context("params", ...).

Local tests post to production

Set base_url: or POSTDEPLOY_INGEST_URL only in development and test.