Make skydb just a ctl-style helper (e.g. apachectl)

sky/tools/skypy/skyserver.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import socket
 import subprocess
 import logging
 import os.path
 
 class SkyServer(object):
     def __init__(self, paths, port, configuration, root):
         self.paths = paths
         self.port = port
         self.configuration = configuration
         self.root = root
         self.server = None
 
     @staticmethod
     def _port_in_use(port):
         sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         return sock.connect_ex(('localhost', port)) == 0
 
     @staticmethod
     def _download_server_if_necessary(paths):
         subprocess.call(os.path.join(paths.sky_tools_directory,
             'download_sky_server'))
         return os.path.join(paths.src_root, 'out', 'downloads', 'sky_server')
 
-    def __enter__(self):
+    def start(self):
         if self._port_in_use(self.port):
             logging.warn(
                 'Port %s already in use, assuming custom sky_server started.' %
                 self.port)
             return
 
         server_path = self._download_server_if_necessary(self.paths)
         server_command = [
             server_path,
             '-t', self.configuration,
             self.root,
             str(self.port),
         ]
         self.server = subprocess.Popen(server_command)
+        return self.server.pid
+
+    def stop(self):
+        if self.server:
+            self.server.terminate()
+
+    def __enter__(self):
+        self.start()
 
     def __exit__(self, exc_type, exc_value, traceback):
-        if self.server:
-            self.server.terminate()
+        self.stop()
 
     def path_as_url(self, path):
         return self.url_for_path(self.port, self.root, path)
 
     @staticmethod
     def url_for_path(port, root, path):
         relative_path = os.path.relpath(path, root)
         return 'http://localhost:%s/%s' % (port, relative_path)