Add automatic pool trimming

lib/puma/server.rb

@@ -25,6 +25,7 @@ module Puma
     attr_accessor :min_threads
     attr_accessor :max_threads
     attr_accessor :persistent_timeout
+    attr_accessor :auto_trim_time
 
     # Create a server for the rack app +app+.
     #
@@ -45,6 +46,7 @@ module Puma
 
       @min_threads = 0
       @max_threads = 16
+      @auto_trim_time = 1
 
       @thread = nil
       @thread_pool = nil
@@ -118,6 +120,10 @@ module Puma
         process_client(client)
       end
 
+      if @auto_trim_time
+        @thread_pool.auto_trim!(@auto_trim_time)
+      end
+
       @thread = Thread.new do
         begin
           check = @check

lib/puma/thread_pool.rb

@@ -24,6 +24,8 @@ module Puma
 
       @workers = []
 
+      @auto_trim = nil
+
       min.times { spawn_thread }
     end
 
@@ -97,9 +99,40 @@ module Puma
       end
     end
 
+    class AutoTrim
+      def initialize(pool, timeout)
+        @pool = pool
+        @timeout = timeout
+        @running = false
+      end
+
+      def start!
+        @running = true
+
+        @thread = Thread.new do
+          while @running
+            @pool.trim
+            sleep @timeout
+          end
+        end
+      end
+
+      def stop
+        @running = false
+        @thread.wakeup
+      end
+    end
+
+    def auto_trim!(timeout=5)
+      @auto_trim = AutoTrim.new(self, timeout)
+      @auto_trim.start!
+    end
+
     # Tell all threads in the pool to exit and wait for them to finish.
     #
     def shutdown
+      @auto_trim.stop if @auto_trim
+
       @spawned.times do
         @todo << Stop
       end

test/test_thread_pool.rb

@@ -99,4 +99,28 @@ class TestThreadPool < Test::Unit::TestCase
 
     assert_equal 1, pool.spawned
   end
+
+  def test_autotrim
+    finish = false
+    pool = new_pool(1, 2) { Thread.pass until finish }
+
+    pool << 1
+    pool << 2
+
+    assert_equal 2, pool.spawned
+
+    finish = true
+
+    pause
+
+    assert_equal 2, pool.spawned
+
+    pool.auto_trim! 1
+
+    sleep 1
+
+    pause
+
+    assert_equal 1, pool.spawned
+  end
 end