More elaborate exception handling. (puma#2700)

* More elaborate exception handling. Fixes puma#2699.

* Add TestIntegrationSingle#test_closed_listener

Co-authored-by: MSP-Greg <Greg.mpls@gmail.com>

lib/puma/server.rb

@@ -356,7 +356,10 @@ def handle_servers
                 pool << client
               end
             end
-          rescue Object => e
+          rescue IOError, Errno::EBADF
+            # In the case that any of the sockets are unexpectedly close.
+            raise
+          rescue StandardError => e
             @events.unknown_error e, nil, "Listen loop"
           end
         end

test/helpers/integration.rb

@@ -50,7 +50,7 @@ def silent_and_checked_system_command(*args)
     assert(system(*args, out: File::NULL, err: File::NULL))
   end
 
-  def cli_server(argv, unix: false, config: nil)
+  def cli_server(argv, unix: false, config: nil, merge_err: false)
     if config
       config_file = Tempfile.new(%w(config .rb))
       config_file.write config
@@ -64,7 +64,11 @@ def cli_server(argv, unix: false, config: nil)
       @tcp_port = UniquePort.call
       cmd = "#{BASE} #{puma_path} #{config} -b tcp://#{HOST}:#{@tcp_port} #{argv}"
     end
-    @server = IO.popen(cmd, "r")
+    if merge_err
+      @server = IO.popen(cmd, "r", :err=>[:child, :out])
+    else
+      @server = IO.popen(cmd, "r")
+    end
     wait_for_server_to_boot
     @pid = @server.pid
     @server

test/rackup/close_listeners.ru

@@ -0,0 +1,6 @@
+require 'objspace'
+
+run lambda { |env|
+  ios = ObjectSpace.each_object(::TCPServer).to_a.tap { |a| a.each(&:close) }
+  [200, [], ["#{ios.inspect}\n"]]
+}

test/test_integration_single.rb

@@ -178,4 +178,29 @@ def test_application_logs_are_flushed_on_write
     @server.close unless @server.closed?
     @server = nil
   end
+
+  # listener is closed 'externally' while Puma is in the IO.select statement
+  def test_closed_listener
+    skip_unless_signal_exist? :TERM
+
+    cli_server "test/rackup/close_listeners.ru", merge_err: true
+    read_body connect
+
+    begin
+      Timeout.timeout(5) do
+        begin
+          Process.kill :SIGTERM, @pid
+        rescue Errno::ESRCH
+        end
+        begin
+          Process.wait2 @pid
+        rescue Errno::ECHILD
+        end
+      end
+    rescue Timeout::Error
+      Process.kill :SIGKILL, @pid
+      assert false, "Process froze"
+    end
+    assert true
+  end
 end