Add thread reaping to thread pool

lib/puma/server.rb

@@ -39,6 +39,7 @@ module Puma
     attr_accessor :max_threads
     attr_accessor :persistent_timeout
     attr_accessor :auto_trim_time
+    attr_accessor :reaping_time
     attr_accessor :first_data_timeout
 
     # Create a server for the rack app +app+.
@@ -60,6 +61,7 @@ module Puma
       @min_threads = 0
       @max_threads = 16
       @auto_trim_time = 1
+      @reaping_time = 1
 
       @thread = nil
       @thread_pool = nil
@@ -274,6 +276,10 @@ module Puma
         @reactor.run_in_thread
       end
 
+      if @reaping_time
+        @thread_pool.auto_reap!(@reaping_time)
+      end
+
       if @auto_trim_time
         @thread_pool.auto_trim!(@auto_trim_time)
       end

lib/puma/thread_pool.rb

@@ -33,6 +33,7 @@ module Puma
       @workers = []
 
       @auto_trim = nil
+      @reaper = nil
 
       @mutex.synchronize do
         @min.times { spawn_thread }
@@ -155,6 +156,21 @@ module Puma
       end
     end
 
+    # If there are dead threads in the pool make them go away while decreasing
+    # spwaned counter so that new healty threads could be created again.
+    def reap
+      @mutex.synchronize do
+        dead_workers = @workers.reject(&:alive?)
+
+        dead_workers.each do |worker|
+          worker.kill
+          @spawned -= 1
+        end
+
+        @workers -= dead_workers
+      end
+    end
+
     class AutoTrim
       def initialize(pool, timeout)
         @pool = pool
@@ -184,6 +200,35 @@ module Puma
       @auto_trim.start!
     end
 
+    class Reaper
+      def initialize(pool, timeout)
+        @pool = pool
+        @timeout = timeout
+        @running = false
+      end
+
+      def start!
+        @running = true
+
+        @thread = Thread.new do
+          while @running
+            @pool.reap
+            sleep @timeout
+          end
+        end
+      end
+
+      def stop
+        @running = false
+        @thread.wakeup
+      end
+    end
+
+    def auto_reap!(timeout=5)
+      @reaper = Reaper.new(self, timeout)
+      @reaper.start!
+    end
+
     # Tell all threads in the pool to exit and wait for them to finish.
     #
     def shutdown
@@ -193,6 +238,7 @@ module Puma
         @not_full.broadcast
 
         @auto_trim.stop if @auto_trim
+        @reaper.stop if @reaper
       end
 
       # Use this instead of #each so that we don't stop in the middle

test/test_thread_pool.rb

@@ -179,4 +179,51 @@ class TestThreadPool < Test::Unit::TestCase
 
     assert_equal [], values.compact
   end
+
+  def test_reap_only_dead_threads
+    pool = new_pool(2,2) { Thread.current.kill }
+
+    assert_equal 2, pool.spawned
+
+    pool << 1
+
+    pause
+
+    assert_equal 2, pool.spawned
+
+    pool.reap
+
+    assert_equal 1, pool.spawned
+
+    pool << 2
+
+    pause
+
+    assert_equal 1, pool.spawned
+
+    pool.reap
+
+    assert_equal 0, pool.spawned
+  end
+
+  def test_auto_reap_dead_threads
+    pool = new_pool(2,2) { Thread.current.kill }
+
+    assert_equal 2, pool.spawned
+
+    pool << 1
+    pool << 2
+
+    pause
+
+    assert_equal 2, pool.spawned
+
+    pool.auto_reap! 1
+
+    sleep 1
+
+    pause
+
+    assert_equal 0, pool.spawned
+  end
 end