Monzo.HTTP.Adapter behaviour (monzo_client v1.0.0)

Behaviour for the low-level HTTP transport used by Monzo.HTTP.

The default implementation, Monzo.HTTP.HttpcAdapter, is built on Erlang's built-in :httpc (part of :inets), keeping monzo free of any required HTTP client dependency (Req, Finch, Tesla, HTTPoison, ...).

Implement this behaviour to plug in your own HTTP client - useful for connection pooling in high-throughput applications, or for injecting a test double in your own test suite (see Monzo.Test.MockAdapter in this library's own tests for an example).

Summary

Types

headers()

method()

request()

response()

Callbacks

request(request, opts)

Performs a single HTTP request and returns the raw response, or an error reason. Implementations should NOT retry - retry/backoff policy is handled by Monzo.HTTP.

Types

headers()

@type headers() :: [{String.t(), String.t()}]

method()

@type method() :: :get | :post | :put | :patch | :delete

request()

@type request() :: %{
  method: method(),
  url: String.t(),
  headers: headers(),
  body: iodata() | nil,
  timeout_ms: pos_integer()
}

response()

@type response() :: %{status: pos_integer(), headers: headers(), body: binary()}

Callbacks

request(request, opts)

@callback request(request(), opts :: term()) :: {:ok, response()} | {:error, term()}

Performs a single HTTP request and returns the raw response, or an error reason. Implementations should NOT retry - retry/backoff policy is handled by Monzo.HTTP.

opts is whatever was configured as the adapter's options (see Monzo.Client.new/1's :adapter option, which accepts either a bare module - in which case opts is nil - or a {module, opts} tuple). This lets test doubles carry explicit state (e.g. an Agent pid) instead of relying on process-dictionary globals, which would break across the process boundaries Monzo.HTTP's retry loop and Monzo.TokenStore introduce.

Return {:error, {:timeout, reason}} for timeouts specifically (so Monzo.HTTP can raise Monzo.Error.TimeoutError rather than a generic network error), and {:error, reason} for any other network failure.