Ensure the application wait thread is unaffected by broken pipes

In certain situations we could not get to the exit_if_finished call and
the thread would just die silently. This would lead to the application
process failing to exit at all, so it would have to be killed with a
SIGKILL.

Author: jonleighton

lib/spring/application.rb

@@ -186,21 +186,7 @@ def serve(client)
       log "forked #{pid}"
       manager.puts pid
 
-      # Wait in a separate thread so we can run multiple commands at once
-      Thread.new {
-        @mutex.synchronize { @waiting += 1 }
-
-        _, status = Process.wait2 pid
-        log "#{pid} exited with #{status.exitstatus}"
-
-        streams.each(&:close)
-        client.puts(status.exitstatus)
-        client.close
-
-        @mutex.synchronize { @waiting -= 1 }
-        exit_if_finished
-      }
-
+      wait pid, streams, client
     rescue Exception => e
       log "exception: #{e}"
       manager.puts unless pid
@@ -296,6 +282,25 @@ def reset_streams
       STDIN.reopen("/dev/null")
     end
 
+    def wait(pid, streams, client)
+      @mutex.synchronize { @waiting += 1 }
+
+      # Wait in a separate thread so we can run multiple commands at once
+      Thread.new {
+        begin
+          _, status = Process.wait2 pid
+          log "#{pid} exited with #{status.exitstatus}"
+
+          streams.each(&:close)
+          client.puts(status.exitstatus)
+          client.close
+        ensure
+          @mutex.synchronize { @waiting -= 1 }
+          exit_if_finished
+        end
+      }
+    end
+
     private
 
     def active_record_configured?

lib/spring/application_manager.rb

@@ -76,6 +76,7 @@ def run(client)
     end
 
     def stop
+      log "stopping"
       @state = :stopping
 
       if pid

lib/spring/server.rb

@@ -92,6 +92,8 @@ def set_exit_hook
     end
 
     def shutdown
+      log "shutting down"
+
       [env.socket_path, env.pidfile_path].each do |path|
         if path.exist?
           path.unlink rescue nil