index.community/backend/lib/backend_web/rate_limiter.ex

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Elixir
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2020-05-19 16:39:33 +00:00
defmodule BackendWeb.RateLimiter do
@moduledoc """
Functions used to rate limit:
* all endpoints by IP/endpoint
* authentication endpoints by domain
"""
import Phoenix.Controller, only: [json: 2]
import Plug.Conn, only: [put_status: 2]
use Plug.Builder
def rate_limit(conn, options \\ []) do
case check_rate(conn, options) do
{:ok, _count} -> conn # Do nothing, allow execution to continue
{:error, _count} -> render_error(conn)
end
end
def rate_limit_authentication(conn, options \\ []) do
%{"id" => domain} = conn.params
options = Keyword.put(options, :bucket_name, "authorization: #{domain}")
rate_limit(conn, options)
end
defp check_rate(conn, options) do
interval_milliseconds = options[:interval_seconds] * 1000
max_requests = options[:max_requests]
bucket_name = options[:bucket_name] || bucket_name(conn)
ExRated.check_rate(bucket_name, interval_milliseconds, max_requests)
end
# Bucket name should be a combination of ip address and request path, like so:
#
# "127.0.0.1:/api/v1/authorizations"
defp bucket_name(conn) do
path = Enum.join(conn.path_info, "/")
ip = conn.remote_ip |> Tuple.to_list |> Enum.join(".")
"#{ip}:#{path}"
end
defp render_error(conn) do
conn
|> put_status(:forbidden)
|> json(%{error: "Rate limit exceeded."})
|> halt # Stop execution of further plugs, return response now
end
end