# `ExResilience.ErrorClassifier`
[🔗](https://github.com/joshrotenberg/ex_resilience/blob/v0.4.0/lib/ex_resilience/error_classifier.ex#L1)

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
    )

# `classification`

```elixir
@type classification() :: :ok | :retriable | :failure | :ignore
```

# `classify`

```elixir
@callback classify(result :: term()) :: classification()
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*