Add a default Isolate gRPC proxy in config

appengine/swarming/swarming_bot/bot_code/bot_main.py

Index: appengine/swarming/swarming_bot/bot_code/bot_main.py
diff --git a/appengine/swarming/swarming_bot/bot_code/bot_main.py b/appengine/swarming/swarming_bot/bot_code/bot_main.py
index 25157f16dc564af18f63822fa12bd530ae16d31e..3ff55f8989b326846f819e97db7e05613c965806 100644
--- a/appengine/swarming/swarming_bot/bot_code/bot_main.py
+++ b/appengine/swarming/swarming_bot/bot_code/bot_main.py
@@ -516,7 +516,7 @@ def get_bot(config):
   attributes = get_attributes(
     bot.Bot(
       remote_client.createRemoteClient(config['server'],
-                                       None, config['is_grpc']),
+                                       None, config.get('swarming_grpc_proxy')),
       attributes,
       config['server'],
       config['server_version'],
@@ -530,7 +530,7 @@ def get_bot(config):
       remote_client.createRemoteClient(
           config['server'],
           lambda: _get_authentication_headers(botobj),
-          config['is_grpc']),
+          config.get('swarming_grpc_proxy')),
       attributes,
       config['server'],
       config['server_version'],
@@ -575,7 +575,7 @@ def _run_isolated_flags(botobj):
   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'),
@@ -583,6 +583,15 @@ def _run_isolated_flags(botobj):
     '--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')
+  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.
@@ -704,7 +713,7 @@ def _run_bot_inner(arg_error, quit_bit):
     # up" the network; if there's something seriously wrong, the handshake will
     # fail and we'll handle it there.
     remote = remote_client.createRemoteClient(config['server'], None,
-                                              config['is_grpc'])
+                                              config.get('swarming_grpc_proxy'))
     remote.ping()
   except Exception:
     # url_read() already traps pretty much every exceptions. This except
@@ -1179,7 +1188,6 @@ def get_config():
     logging.exception('Invalid config.json!')
     config = {
       'enable_ts_monitoring': False,
-      'is_grpc': False,
       'server': '',
       'server_version': 'version1',
     }