Implement add_idle_workers!/2 (#97)

CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added function `add_idle_workers!/2` for adding some idle workers to the initialized pool in runtime.
+
+### Changed
+
+- Refactored private `start_workers` function. It no longer accepts monitor_id as it already is in the state.
+
 ## [0.9.0] - 2024-04-24
 
 ### Added

lib/poolex.ex

@@ -253,6 +253,21 @@ defmodule Poolex do
     GenServer.call(pool_id, :get_debug_info)
   end
 
+  @doc """
+  Adds some idle workers to existing pool.
+  """
+  @spec add_idle_workers!(pool_id(), pos_integer()) :: :ok | no_return()
+  def add_idle_workers!(_pool_id, workers_count) when workers_count < 1 do
+    message = "workers_count must be positive number, received: #{inspect(workers_count)}"
+
+    raise ArgumentError, message
+  end
+
+  def add_idle_workers!(pool_id, workers_count)
+      when is_atom(pool_id) and is_integer(workers_count) do
+    GenServer.call(pool_id, {:add_idle_workers, workers_count})
+  end
+
   @impl GenServer
   def init(opts) do
     Process.flag(:trap_exit, true)
@@ -285,7 +300,7 @@ defmodule Poolex do
         worker_start_fun: worker_start_fun
       }
 
-    initial_workers_pids = start_workers(workers_count, state, monitor_id)
+    initial_workers_pids = start_workers(workers_count, state)
 
     state =
       state
@@ -303,20 +318,20 @@ defmodule Poolex do
     {:noreply, state}
   end
 
-  @spec start_workers(non_neg_integer(), State.t(), Monitoring.monitor_id()) :: [pid]
-  defp start_workers(0, _state, _monitor_id) do
+  @spec start_workers(non_neg_integer(), State.t()) :: [pid]
+  defp start_workers(0, _state) do
     []
   end
 
-  defp start_workers(workers_count, _state, _monitor_id) when workers_count < 0 do
+  defp start_workers(workers_count, _state) when workers_count < 0 do
     msg = "workers_count must be non negative number, received: #{inspect(workers_count)}"
     raise ArgumentError, msg
   end
 
-  defp start_workers(workers_count, state, monitor_id) do
+  defp start_workers(workers_count, state) do
     Enum.map(1..workers_count, fn _ ->
       {:ok, worker_pid} = start_worker(state)
-      Monitoring.add(monitor_id, worker_pid, :worker)
+      Monitoring.add(state.monitor_id, worker_pid, :worker)
 
       worker_pid
     end)
@@ -367,7 +382,7 @@ defmodule Poolex do
     {:reply, state, state}
   end
 
-  def handle_call(:get_debug_info, _form, %State{} = state) do
+  def handle_call(:get_debug_info, _from, %State{} = state) do
     debug_info = %DebugInfo{
       busy_workers_count: BusyWorkers.count(state),
       busy_workers_impl: state.busy_workers_impl,
@@ -387,6 +402,18 @@ defmodule Poolex do
     {:reply, debug_info, state}
   end
 
+  @impl GenServer
+  def handle_call({:add_idle_workers, workers_count}, _from, %State{} = state) do
+    new_state =
+      workers_count
+      |> start_workers(state)
+      |> Enum.reduce(state, fn worker, acc_state ->
+        IdleWorkers.add(acc_state, worker)
+      end)
+
+    {:reply, :ok, new_state}
+  end
+
   @impl GenServer
   def handle_cast({:release_busy_worker, worker}, %State{} = state) do
     if WaitingCallers.empty?(state) do

test/poolex_test.exs

@@ -4,6 +4,8 @@ defmodule PoolexTest do
 
   doctest Poolex
 
+  alias Poolex.Private.DebugInfo
+
   describe "debug info" do
     test "valid after initialization" do
       initial_fun = fn -> 0 end
@@ -12,7 +14,7 @@ defmodule PoolexTest do
 
       debug_info = Poolex.get_debug_info(pool_name)
 
-      assert debug_info.__struct__ == Poolex.Private.DebugInfo
+      assert debug_info.__struct__ == DebugInfo
       assert debug_info.busy_workers_count == 0
       assert debug_info.busy_workers_impl == Poolex.Workers.Impl.List
       assert debug_info.busy_workers_pids == []
@@ -51,7 +53,7 @@ defmodule PoolexTest do
 
       debug_info = Poolex.get_debug_info(pool_name)
 
-      assert debug_info.__struct__ == Poolex.Private.DebugInfo
+      assert debug_info.__struct__ == DebugInfo
       assert debug_info.busy_workers_count == 0
       assert Enum.empty?(debug_info.busy_workers_pids)
       assert debug_info.idle_workers_count == 5
@@ -80,7 +82,7 @@ defmodule PoolexTest do
 
       debug_info = Poolex.get_debug_info(pool_name)
 
-      assert debug_info.__struct__ == Poolex.Private.DebugInfo
+      assert debug_info.__struct__ == DebugInfo
       assert debug_info.busy_workers_count == 1
       assert Enum.count(debug_info.busy_workers_pids) == 1
       assert debug_info.idle_workers_count == 4
@@ -582,4 +584,30 @@ defmodule PoolexTest do
       assert elem(message_3, 3) == pool_pid
     end
   end
+
+  describe "add_idle_workers!/2" do
+    test "adds idle workers to pool" do
+      initial_fun = fn -> 0 end
+
+      pool_name = start_pool(worker_module: Agent, worker_args: [initial_fun], workers_count: 5)
+
+      assert %DebugInfo{idle_workers_count: 5} = Poolex.get_debug_info(pool_name)
+      assert :ok = Poolex.add_idle_workers!(pool_name, 5)
+      assert %DebugInfo{idle_workers_count: 10} = Poolex.get_debug_info(pool_name)
+    end
+
+    test "raises error on non positive workers_count" do
+      initial_fun = fn -> 0 end
+
+      pool_name = start_pool(worker_module: Agent, worker_args: [initial_fun], workers_count: 5)
+
+      assert_raise(ArgumentError, fn ->
+        Poolex.add_idle_workers!(pool_name, -1)
+      end)
+
+      assert_raise(ArgumentError, fn ->
+        Poolex.add_idle_workers!(pool_name, 0)
+      end)
+    end
+  end
 end