ash/documentation/concepts/timeouts.md

Timeouts

Timeouts in Ash work a bit differently than other tools. The following considerations must be taken into account:

1. If you run a resource action in a transaction, then the timeout applies to the entire transaction.
2. If the resource action you are running, and any of its touches_resources is already in a transaction then the timeout is ignored, as the outer transaction is handling the timeout.
3. If the resource is not in a transaction, then the timeout is applied to each query that is run. Ash may run many queries to fulfill the action, so keep in mind that the request can take considerably longer than the specified timeout. No single query will be allowed to take longer than that timeout, however. The practical implications here is that create/update/destroy actions with a timeout will honor that timeout because they default to transaction?: true. If you wish to specify a holistic timeout for read actions, then you must specify transaction?: true, timeout: timeout.
4. If the data layer of the resource does not support timeouts, then timeouts are ignored.
5. As of the writing of this guide, none of the API extensions support specifying a timeout, but the general idea is that if you need "holistic" timeouts for an action or a request, you have two options: if you are calling your resources with hand written code, run the code in a Task and await it with a timeout. If you are using an API extension, add the timeouts to the configuration of those extensions, as they can easily be configured to run requests in a Task with a timeout in the same way.

Ways to Specify Timeouts

You have a few options.

You can specify a timeout when you call an action. This takes the highest precedence.

MyApi.read!(query, timeout: :timer.seconds(30))

You can specify one using Ash.Changeset.timeout/2 or Ash.Query.timeout/2. This can be useful if you want to conditionally set a timeout based on the details of the request. For example, you might:

# in your resource
defmodule MyApp.SetReportTimeout do
  use Ash.Resource.Preparation

  def prepare(query, _, _) do
    if Ash.Query.get_argument(query, :full_report) do
      Ash.Query.timeout(query, :timer.minutes(3))
    else
      Ash.Query.timeout(query, :timer.minutes(1))
    end
  end
end

actions do
  read :report_items do
    argument :full_report, :boolean, default: false

    prepare MyApp.SetReportTimeout
  end
end

And you can specify a default timeout on the Api module that you call your resources with. Overriding an api with a default timeout requires providing a timeout of :infinity in one of the other methods.

execution do
  timeout :timer.seconds(30) # this is the default
end