server/client - rate limiting for threads/replies

lib/myapp/rate_limiter.ex

@@ -0,0 +1,18 @@
+defmodule MyApp.RateLimiter do
+
+  # map keys to integers to save memory
+  def new_reply_key, do: 1
+  def new_thread_key, do: 2
+
+  @spec limit(String.t, integer, integer) :: {:ok, String.t} | {:error, String.t}
+  def limit(end_point, user_id, seconds) do
+    key = "rl#{end_point}:#{user_id}"
+    case Cachex.get(:myapp, key) do
+      {:missing, _} ->
+        Cachex.set(:myapp, key, true, ttl: :timer.seconds(seconds))
+        {:ok, "ok"}
+      {:ok, _} -> {:error, "limit reached"}
+    end
+  end
+
+end