swarmbucket: add get_builders api

appengine/cr-buildbucket/swarming/swarmbucket_api.py

Index: appengine/cr-buildbucket/swarming/swarmbucket_api.py
diff --git a/appengine/cr-buildbucket/swarming/swarmbucket_api.py b/appengine/cr-buildbucket/swarming/swarmbucket_api.py
new file mode 100644
index 0000000000000000000000000000000000000000..b9180a78a8bce5eda73d3e0441ed5483eebb5ac3
--- /dev/null
+++ b/appengine/cr-buildbucket/swarming/swarmbucket_api.py
@@ -0,0 +1,87 @@
+# Copyright 2016 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.
+
+from google.appengine.ext import ndb
+from protorpc import messages
+from protorpc import message_types
+from protorpc import remote
+
+from components import auth
+from components import utils
+import gae_ts_mon
+
+import acl
+import config
+
+
+def swarmbucket_api_method(
+    request_message_class, response_message_class, **kwargs):
+  """Defines a swarmbucket API method."""
+
+  endpoints_decorator = auth.endpoints_method(
+      request_message_class, response_message_class, **kwargs)
+
+  def decorator(fn):
+    fn = auth.public(fn)
+    fn = endpoints_decorator(fn)
+    fn = ndb.toplevel(fn)
+    def ts_mon_time():
+      return utils.datetime_to_timestamp(utils.utcnow()) / 1000000.0
+    fn = gae_ts_mon.instrument_endpoint(time_fn=ts_mon_time)(fn)
+    return fn
+
+  return decorator
+
+
+class BuilderMessage(messages.Message):
+  name = messages.StringField(1)
+  category = messages.StringField(2)
+
+
+class BucketMessage(messages.Message):
+  # Bucket name. Unique per buildbucket instance.
+  name = messages.StringField(1)
+  builders = messages.MessageField(BuilderMessage, 2, repeated=True)
+
+
+class GetBuildersResponseMessage(messages.Message):
+  buckets = messages.MessageField(BucketMessage, 1, repeated=True)
+
+
+@auth.endpoints_api(
+  name='swarmbucket', version='v1',
+  title='Buildbucket-Swarming integration')
+class SwarmbucketApi(remote.Service):
+  """API specific to swarmbucket."""
+
+  @swarmbucket_api_method(
+      message_types.VoidMessage,
+      GetBuildersResponseMessage,
+      path='builders', http_method='GET')
+  def get_builders(self, _request):
+    """Returns defined swarmbucket builders.
+
+    Can be used by code review tool to discover builders.
+    """
+    buckets = config.get_buckets_async().get_result()
+    available = acl.get_available_buckets()
+    if available is not None:  # pragma: no branch
+      available = set(available)
+      buckets = [b for b in buckets if b.name in available]
+
+    res = GetBuildersResponseMessage()
+    for bucket in buckets:
+      if not bucket.swarming.builders:
+        continue
+      res.buckets.append(BucketMessage(
+        name=bucket.name,
+        builders=[
+          BuilderMessage(
+            name=builder.name,
+            category=builder.category,
+          )
+          for builder in bucket.swarming.builders
+        ],
+      ))
+    return res