Fix slow rollout of new generation workers

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Unreleased
 
+- Fix the slow rollout of workers on a new generation.
 - Expose `Pitchfork::Info.fork_safe?` and `Pitchfork::Info.no_longer_fork_safe!`.
 
 # 0.6.0

lib/pitchfork/http_server.rb

@@ -635,9 +635,11 @@ def restart_outdated_workers
         outdated_workers.each do |worker|
           if worker.soft_kill(:TERM)
             logger.info("Sent SIGTERM to worker=#{worker.nr} pid=#{worker.pid} gen=#{worker.generation}")
+            workers_to_restart -= 1
           else
             logger.info("Failed to send SIGTERM to worker=#{worker.nr} pid=#{worker.pid} gen=#{worker.generation}")
           end
+          break if workers_to_restart <= 0
         end
       end
     end

test/integration/test_reforking.rb

@@ -107,5 +107,46 @@ def test_reforking_on_USR2
       assert_healthy("http://#{addr}:#{port}")
       assert_clean_shutdown(pid)
     end
+
+    def test_slow_worker_rollout
+      addr, port = unused_port
+
+      pid = spawn_server(app: File.join(ROOT, "test/integration/env.ru"), config: <<~CONFIG)
+        listen "#{addr}:#{port}"
+        worker_processes 5
+        after_worker_fork do |_server, worker|
+          Kernel.at_exit do
+            sleep 0.1
+          end
+        end
+      CONFIG
+
+      assert_healthy("http://#{addr}:#{port}")
+      assert_stderr "worker=0 gen=0 ready"
+      assert_stderr "worker=4 gen=0 ready"
+
+      Process.kill(:USR2, pid)
+
+      assert_stderr "worker=0 gen=1 ready"
+      assert_stderr "worker=1 gen=1 ready"
+      assert_stderr "worker=2 gen=1 ready"
+      assert_stderr "worker=3 gen=1 ready"
+      assert_stderr "worker=4 gen=1 ready"
+
+      assert_clean_shutdown(pid)
+
+      log_lines = read_stderr.lines.drop_while { |l| !l.match?(/Terminating old mold/) }
+      log_lines = log_lines.take_while { |l| !l.match?(/QUIT received/) }
+
+      events = log_lines.map do |line|
+        case line
+        when /Sent SIGTERM to worker/
+          :term
+        when /registered/
+          :registered
+        end
+      end.compact
+      assert_equal([:term, :registered] * 5, events)
+    end
   end
 end