Stop SolidQueue on puma restart when puma plugin is used.

Without doing so SolidQueue would be running making Puma not properly stop so whne Puma tries to
start its process again we would get `Errno::EADDRINUSE` error.

Author: nashby

lib/puma/plugin/solid_queue.rb

@@ -19,6 +19,7 @@ def start(launcher)
     end
 
     launcher.events.on_stopped { stop_solid_queue }
+    launcher.events.on_restart { stop_solid_queue }
   end
 
   private

test/integration/puma/plugin_test.rb

@@ -4,27 +4,32 @@
 class PumaPluginTest < ActiveSupport::TestCase
   self.use_transactional_tests = false
 
+  def puma_pid
+    File.read(Rails.root.join('tmp', 'pids', 'server.pid')).to_i
+  end
+
   setup do
     FileUtils.mkdir_p Rails.root.join("tmp", "pids")
 
-    cmd = %w[
-      bundle exec puma
-        -b tcp://127.0.0.1:9222
-        -C test/dummy/config/puma.rb
-        --dir test/dummy
-        -s
-        config.ru
-    ]
-
-    @pid = fork do
-      exec(*cmd)
+    Dir.chdir('test/dummy') do
+      cmd = %w[
+        bundle exec puma
+          -b tcp://127.0.0.1:9222
+          -C config/puma.rb
+          -s
+          config.ru
+      ]
+
+      fork do
+        exec(*cmd)
+      end
     end
 
     wait_for_registered_processes(4, timeout: 3.second)
   end
 
   teardown do
-    terminate_process(@pid, signal: :INT)
+    terminate_process(puma_pid, signal: :INT)
     wait_for_registered_processes 0, timeout: 0.2.second
 
     JobResult.delete_all
@@ -36,4 +41,14 @@ class PumaPluginTest < ActiveSupport::TestCase
     wait_for_jobs_to_finish_for(1.second)
     assert_equal 1, JobResult.where(queue_name: :background, status: "completed", value: :puma_plugin).count
   end
+
+  test "stop the queue on puma's restart" do
+    signal_process(puma_pid, :SIGUSR2)
+
+    wait_for_registered_processes(4, timeout: 3.second)
+
+    StoreResultJob.perform_later(:puma_plugin)
+    wait_for_jobs_to_finish_for(1.second)
+    assert_equal 1, JobResult.where(queue_name: :background, status: "completed", value: :puma_plugin).count
+  end
 end