Add a test for of the child dies during the reexec

test/integration/_lib/fixtures/exit_during_upgrade/exiting_server.rb

@@ -0,0 +1,22 @@
+require 'bundler/setup'
+require 'socket'
+require 'einhorn/worker'
+
+def einhorn_main
+  serv = Socket.for_fd(Einhorn::Worker.socket!)
+  Einhorn::Worker.ack!
+
+  Signal.trap('USR2') do
+    sleep 3
+    exit!
+  end
+
+  while true
+    s, _ = serv.accept
+    s.write($$)
+    s.flush
+    s.close
+  end
+end
+
+einhorn_main if $0 == __FILE__

test/integration/_lib/fixtures/exit_during_upgrade/upgrade_reexec.rb

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+if [ "$1" = "--with-state-fd" ]; then
+  sleep 6
+fi
+exec bundle exec --keep-file-descriptors einhorn "$@"

test/integration/upgrading.rb

@@ -1,5 +1,6 @@
 require(File.expand_path('_lib', File.dirname(__FILE__)))
 require 'socket'
+require 'einhorn/client'
 
 class UpgradeTests < EinhornIntegrationTestCase
   include Helpers::EinhornHelpers
@@ -53,6 +54,34 @@ class UpgradeTests < EinhornIntegrationTestCase
         end
       end
 
+      it 'cleans up if a child dies during the reexec' do
+        # attempt to setup a scenario where a child exits in the
+        # interlude after old einhorn has execed the reexec-as
+        # command, but before the reexec-as command execs new einhorn
+
+        @dir = prepare_fixture_directory('exit_during_upgrade')
+        @server_program = File.join(@dir, "exiting_server.rb")
+        @socket_path = File.join(@dir, "einhorn.sock")
+
+        reexec_cmdline = File.join(@dir, 'upgrade_reexec.rb')
+
+        with_running_einhorn(%W{einhorn -m manual -b 127.0.0.1:#{@port} --reexec-as=#{reexec_cmdline} -d #{@socket_path} -- ruby #{@server_program}}) do |process|
+          wait_for_open_port
+
+          Process.kill('USR2', read_from_port.to_i)
+          einhornsh(%W{-d #{@socket_path} -e upgrade})
+
+          client = Einhorn::Client.for_path(@socket_path)
+          client.send_command('command' => 'state')
+          resp = client.receive_message
+
+          state = YAML.load(resp['message'])
+          assert_equal(1, state[:state][:children].count)
+
+          process.terminate
+        end
+      end
+
       describe 'without preloading' do
         it 'can update environment variables when the reexec command line says to' do
           # exec the new einhorn with the same environment: