Use config.json to enable Isolated gRPC proxy

appengine/swarming/swarming_bot/bot_code/bot_main.py

 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Swarming bot main process.
 
 This is the program that communicates with the Swarming server, ensures the code
 is always up to date and executes a child process to run tasks and upload
 results back.
 
@@ skipping 557 matching lines @@
   """Returns flags to pass to run_isolated.
 
   These are not meant to be processed by task_runner.py.
   """
   settings = _get_settings(botobj)
   partition = settings['free_partition']
   size = os_utilities.get_disk_size(THIS_FILE)
   min_free = (
       _min_free_disk({'size_mb': size}, partition) +
       partition['wiggle'])
-  return [
+  args = [
     '--cache', os.path.join(botobj.base_dir, 'isolated_cache'),
     '--min-free-space', str(min_free),
     '--named-cache-root', os.path.join(botobj.base_dir, 'c'),
     '--max-cache-size', str(settings['caches']['isolated']['size']),
     '--max-items', str(settings['caches']['isolated']['items']),
   ]
 
+  # Get the gRPC proxy from the config, but allow an environment variable to
+  # override.
+  grpc_proxy = get_config().get('isolate-grpc-proxy')

[Vadim Sh., 2017/06/29 19:00:18]

use underscores, so it is a valid proto field name: isolate_grpc_proxy (I think
eventually config.json is assembled form a proto message)

Also other config.json fields use underscores now.

[aludwin, 2017/06/29 19:14:30]

Done.

+  grpc_proxy = os.environ.get('ISOLATE_GRPC_PROXY', grpc_proxy)
+  if grpc_proxy is not None:
+    logging.info('Isolate will use gRPC proxy %s', grpc_proxy)
+    args.extend(['--grpc-proxy', grpc_proxy])
+  return args
+
 
 def _clean_cache(botobj):
   """Asks run_isolated to clean its cache.
 
   This may take a while but it ensures that in the case of a run_isolated run
   failed and it temporarily used more space than _min_free_disk, it can cleans
   up the mess properly.
 
   It will remove unexpected files, remove corrupted files, trim the cache size
   based on the policies and update state.json.
@@ skipping 627 matching lines @@
   error = None
   if len(args.unsupported) != 0:
     error = 'Unexpected arguments: %s' % args
   try:
     return _run_bot(error)
   finally:
     _call_hook_safe(
         True, bot.Bot(None, None, None, None, base_dir, None),
         'on_bot_shutdown')
     logging.info('main() returning')