Fix behaviour of max_waiting = 0 with max_running = 1

CHANGELOG.md

@@ -13,6 +13,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 
 - Decrement counter when max retries has been reached.
+- Fixes behaviour of `max_waiting = 0` with `max_size = 1`.
 
 ## [0.1.0] - 2020-05-16
 

lib/concurrent_limiter.ex

@@ -127,6 +127,13 @@ defmodule ConcurrentLimiter do
           scope: "max"
         })
 
+      max_waiting == 0 ->
+        :telemetry.execute([:concurrent_limiter, :overload], %{counter: counter}, %{limiter: name, scope: "max"})
+        dec(ref, name)
+        {:error, :overload}
+
+       counter > max ->
+        :telemetry.execute([:concurrent_limiter, :overload], %{counter: counter}, %{limiter: name, scope: "max"})
         dec(ref, name)
         {:error, :overload}
 

test/concurrent_limiter_test.exs

@@ -6,6 +6,17 @@ defmodule ConcurrentLimiterTest do
   use ExUnit.Case
   doctest ConcurrentLimiter
 
+  test "limited to one" do
+    name = "l1"
+    ConcurrentLimiter.new(name, 1, 0, max_retries: 0)
+    endless = fn() -> :timer.sleep(10000) end
+    spawn(fn() -> ConcurrentLimiter.limit(name, endless) end)
+    :timer.sleep(5)
+    {:error, :overload} = ConcurrentLimiter.limit(name, endless)
+    {:error, :overload} = ConcurrentLimiter.limit(name, endless)
+    {:error, :overload} = ConcurrentLimiter.limit(name, endless)
+  end
+
   test "limiter is atomic" do
     name = "test"
     ConcurrentLimiter.new(name, 2, 2)