config services: services.cfg and validation

appengine/config_service/services.py

Index: appengine/config_service/services.py
diff --git a/appengine/config_service/services.py b/appengine/config_service/services.py
new file mode 100644
index 0000000000000000000000000000000000000000..1489b2fd9d17f8cb54659ef453b57216e20abfb8
--- /dev/null
+++ b/appengine/config_service/services.py
@@ -0,0 +1,79 @@
+# Copyright 2015 The Swarming Authors. All rights reserved.
+# Use of this source code is governed by the Apache v2.0 license that can be
+# found in the LICENSE file.
+
+"""Provides info about registered luci services."""
+
+from components import config
+from components import net
+from components import utils
+
+from google.appengine.ext import ndb
+
+from proto import service_config_pb2
+import common
+import storage
+import validation
+
+
+class DynamicMetadataError(Exception):
+  """Raised when a service metadata endpoint response is bad."""
+
+
+@ndb.tasklet
+def get_services_async():
+  """Returns a list of registered luci services.
+
+  The list is stored in services/luci-config:services.cfg. Never returns None.
+  Cached.
+  """
+  cfg = yield storage.get_self_config_async(
+      common.SERVICES_REGISTRY_FILENAME, service_config_pb2.ServicesCfg)
+  raise ndb.Return(cfg.services or [])
+
+
+@ndb.tasklet
+def _get_service_async(service_id):
+  services = yield get_services()
+  for service in services:
+    if service.id == service_id:
+      raise ndb.Return(service)
+
+
+def _dict_to_dynamic_metadata(data):
+  validation.validate_service_dynamic_metadata_blob(
+      data,
+      config.validation.Context.raise_on_error(exc_type=DynamicMetadataError))
+
+  metadata = service_config_pb2.ServiceDynamicMetadata()
+  validation_meta = data.get('validation')
+  if validation_meta:
+    metadata.validation.url = validation_meta['url']
+    for p in validation_meta.get('patterns', []):
+      pattern = metadata.validation.patterns.add()
+      pattern.config_set=p['config_set']
+      pattern.path=p['path']
+  return metadata
+
+
+@utils.memcache_async('service_metadata', ['service_id'], time=60)
+def get_metadata_async(service_id):
+  """Returns service dynamic metadata.
+
+  Memcaches results for 1 min. Never returns None.
+
+  Raises:
+    DynamicMetadataError if metadata endpoint response is bad.
+  """
+  service = yield _get_service_async(service_id)
+  if service is None:
+    raise ValueError('Service "%s" not found', service_id)
+
+  if not service.metadata_url:
+    raise ndb.Return(service_config_pb2.ServiceDynamicMetadata())
+
+  try:
+    res = net.json_request_async(service.metadata_url)
+  except net.Error as ex:
+    raise DynamicMetadataError('Net error: %s' % ex.message)
+  raise ndb.Return(_dict_to_dynamic_metadata(res))