Behaviour for classifying function results.

Implement this behaviour to control how patterns respond to different results. A single classifier can be shared across all patterns in a pipeline.

Classifications

• :ok -- success. Resets circuit breaker failure count.
• :retriable -- transient error. Retry will attempt again. Counts as failure for circuit breaker.
• :failure -- permanent error. Do not retry. Counts as failure for circuit breaker.
• :ignore -- do not count as success or failure. Circuit breaker ignores. Retry does not retry.

Examples

A custom classifier that treats timeouts as retriable but authorization errors as permanent failures:

defmodule MyApp.Classifier do
  @behaviour ExResilience.ErrorClassifier

  @impl true
  def classify({:error, :timeout}), do: :retriable
  def classify({:error, :econnrefused}), do: :retriable
  def classify({:error, :unauthorized}), do: :failure
  def classify({:error, _}), do: :failure
  def classify(_), do: :ok
end

Pass the module to any pattern via the :error_classifier option:

ExResilience.CircuitBreaker.start_link(
  name: :my_cb,
  error_classifier: MyApp.Classifier
)