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..55e3849d49788351620e679868fc196d123a63c7
--- /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):

[Vadim Sh., 2016/05/24 19:22:59]

no arguments? How would we support different projects (that need different set
of builders)?

Also, is it really swarming specific? Can't it replace current halfassed
rietveld builder config mechanism for CQ builders? (Or it was fixed already?)

[nodir, 2016/05/24 19:36:54]

I added "bucket" parameter initially, and then deleted it. Currently we don't
have a use case that needs filtering and filtering can be always added later.
 
it is swarmbucket-specific because, but in general concepts "builder" and
"category" are well-established across infra.
Eventually? Maybe. My plan is to fetch builders from this endpoints _in
addition_ to existing mechanisms.

+    """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:
+      available = set(available)
+      buckets = [b for b in buckets if b.name in available]
+
+    res = GetBuildersResponseMessage()
+    for bucket in buckets:
+      if not bucket.swarming or 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