Use config.json to enable Isolated gRPC proxy

The values in config.json are not set yet and will be added in a future
change.

BUG=

Review-Url: https://codereview.chromium.org/2969463002

appengine/swarming/swarming_bot/bot_code/bot_main.py

@@ -575,14 +575,23 @@ 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'),
     '--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')
+  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.

client/isolate_storage.py

@@ -54,9 +54,9 @@
 DOWNLOAD_READ_TIMEOUT = 60
 
 
-# A class to use to communicate with the server by default. Can be changed by
-# 'set_storage_api_class'. Default is IsolateServer.
-_storage_api_cls = None
+# Stores the gRPC proxy address. Must be set if the storage API class is
+# IsolateServerGrpc (call 'set_grpc_proxy').
+_grpc_proxy = None
 
 
 class Item(object):
@@ -527,7 +527,7 @@ class IsolateServerGrpc(StorageApi):
   while fetching.
   """
 
-  def __init__(self, server, namespace):
+  def __init__(self, server, namespace, proxy):
     super(IsolateServerGrpc, self).__init__()
     logging.info('Using gRPC for Isolate')
     self._server = server
@@ -545,9 +545,8 @@ def __init__(self, server, namespace):
     assert grpc
     assert bytestream_pb2
 
-    proxy = os.environ.get('ISOLATED_GRPC_PROXY', '')
-    roots = os.environ.get('ISOLATED_GRPC_PROXY_TLS_ROOTS')
-    overd = os.environ.get('ISOLATED_GRPC_PROXY_TLS_OVERRIDE')
+    roots = os.environ.get('ISOLATE_GRPC_PROXY_TLS_ROOTS')
+    overd = os.environ.get('ISOLATE_GRPC_PROXY_TLS_OVERRIDE')
 
     # The "proxy" envvar must be of the form:
     # http[s]://<server>[:port][/prefix]
@@ -700,12 +699,11 @@ def contains(self, items):
     return missing_items
 
 
-def set_storage_api_class(cls):
-  """Replaces StorageApi implementation used by default."""
-  global _storage_api_cls
-  assert _storage_api_cls is None
-  assert issubclass(cls, StorageApi)
-  _storage_api_cls = cls
+def set_grpc_proxy(proxy):
+  """Sets the StorageApi to use the specified proxy."""
+  global _grpc_proxy
+  assert _grpc_proxy is None
+  _grpc_proxy = proxy
 
 
 def get_storage_api(url, namespace):
@@ -724,5 +722,6 @@ def get_storage_api(url, namespace):
   Returns:
     Instance of StorageApi subclass.
   """
-  cls = _storage_api_cls or IsolateServer
-  return cls(url, namespace)
+  if _grpc_proxy is not None:
+    return IsolateServerGrpc(url, namespace, _grpc_proxy)
+  return IsolateServer(url, namespace)

client/isolateserver.py

@@ -1949,7 +1949,7 @@ def add_isolate_server_options(parser):
            'variable ISOLATE_SERVER if set. No need to specify https://, this '
            'is assumed.')
   parser.add_option(
-      '--is-grpc', action='store_true', help='Communicate to Isolate via gRPC')
+      '--grpc-proxy', help='gRPC proxy by which to communicate to Isolate')
   parser.add_option(
       '--namespace', default='default-gzip',
       help='The namespace to use on the Isolate Server, default: %default')
@@ -1966,11 +1966,8 @@ def process_isolate_server_options(
       parser.error('--isolate-server is required.')
     return
 
-  if 'ISOLATED_GRPC_PROXY' in os.environ:
-    options.is_grpc = True
-
-  if options.is_grpc:
-    isolate_storage.set_storage_api_class(isolate_storage.IsolateServerGrpc)
+  if options.grpc_proxy:
+    isolate_storage.set_grpc_proxy(options.grpc_proxy)
   else:
     try:
       options.isolate_server = net.fix_url(options.isolate_server)

client/tests/isolate_storage_test.py

@@ -59,9 +59,9 @@ def raiseError(code):
 
 class IsolateStorageTest(auto_stub.TestCase):
   def get_server(self):
-    os.environ['ISOLATED_GRPC_PROXY'] = 'https://luci.com/client/bob'
     return isolate_storage.IsolateServerGrpc('https://luci.appspot.com',
-                                             'default-gzip')
+                                             'default-gzip',
+                                             'https://luci.com/client/bob')
 
   def testFetchHappySimple(self):
     """Fetch: if we get a few chunks with the right offset, everything works"""