config services: services.cfg and validation

appengine/components/components/config/endpoint.py

Index: appengine/components/components/config/endpoint.py
diff --git a/appengine/components/components/config/endpoint.py b/appengine/components/components/config/endpoint.py
index e7c9e4ebd31b0cb7f941c0b8c8716993b10c5df8..06ac5f3489a15c40aae027fd21ee1d8b64a80c2d 100644
--- a/appengine/components/components/config/endpoint.py
+++ b/appengine/components/components/config/endpoint.py
@@ -5,7 +5,8 @@
 """Cloud Endpoints API for configs.
 
 * Reads/writes config service location.
-* Validates configs. TODO(nodir): implement.
+* Validates configs.
+* Provides service metadata.
 """
 
 import logging
@@ -18,6 +19,11 @@ from protorpc import remote
 from . import common
 from . import validation
 
+METADATA_FORMAT_VERSION = "1.0"
+
+def get_default_rule_set():
+  return validation.DEFAULT_RULE_SET
+
 
 class ConfigSettingsMessage(messages.Message):
   """Configuration service location."""
@@ -46,6 +52,50 @@ class ValidateResponseMessage(messages.Message):
   messages = messages.MessageField(ValidationMessage, 1, repeated=True)
 
 
+def is_trusted_requester():

[Vadim Sh., 2015/07/08 03:05:58]

I propose to reduce magicallity and store trusted_config_account in
common.ConfigSettings explicitly (as "user:abc@gserviceaccount.com"). That way
you don't need to mention googleplex; it works for non-default versions; it
works on local dev server (e.g. one can put 'anonymous:anonymous' there or
whatever).

[nodir, 2015/07/08 15:24:47]

Done.

+  """Returns True if the requester can see the service metadata.
+
+  Used in metadata endpoint.
+
+  Returns:
+    True if the current identity is an admin or the config service.
+  """
+  if auth.is_admin():
+    return True
+
+  identity = auth.get_current_identity()
+  if identity.is_user:
+    settings = common.ConfigSettings.cached()
+    if settings and settings.service_hostname:
+      parts = settings.service_hostname.split('.')
+      trusted_domains = ('appspot', 'googleplex')
+      # Does not work for tainted versions.
+      if len(parts) > 2 and parts[-1] == 'com' and parts[-2] in trusted_domains:
+        trusted_config_account = (
+            '%s@%s.gserviceaccount.com' % (parts[-3], parts[-2]))
+        if identity.name == trusted_config_account:
+          return True
+
+  return False
+
+
+class ConfigPattern(messages.Message):
+  """A pattern for one config file. See MetadataResponseMessage."""
+  config_set = messages.StringField(1, required=True)
+  path = messages.StringField(2, required=True)
+
+
+class MetadataResponseMessage(messages.Message):
+  """Compatible with config service's ServiceDynamicMetadata messsage."""

[Vadim Sh., 2015/07/08 03:05:58]

Describe exactly what you mean by "compatible", e.g. "If you add a field to
*.proto, add exact same field here too" (IIUC).

Also it might be better to name it exactly as proto message class.

[nodir, 2015/07/08 15:24:47]

Done.

+
+  class Validator(messages.Message):
+    patterns = messages.MessageField(ConfigPattern, 1, repeated=True)
+    url = messages.StringField(2, required=True)
+
+  version = messages.StringField(1, required=True)

[Vadim Sh., 2015/07/08 03:05:58]

Is it needed? Proto-flavored formats are supposed to be eternally backward
compatible (until API version switches at least).

[nodir, 2015/07/08 15:24:47]

config services talks to different services that may have different versions of
metadata formats. The API version is specified implicitly, as a part of URL in
services.cfg, so API versioning does not really work in this case. Finally, a
metadata endpoint does not have to be a cloud endpoints thing

+  validation = messages.MessageField(Validator, 2)
+
+
 @auth.endpoints_api(name='config', version='v1', title='Configuration service')
 class ConfigApi(remote.Service):
   """Configuration service."""
@@ -85,3 +135,24 @@ class ConfigApi(remote.Service):
           text=m.text,
       ))
     return res
+
+  @auth.endpoints_method(
+      message_types.VoidMessage, MetadataResponseMessage, path='metadata')
+  @auth.require(is_trusted_requester)
+  def get_metadata(self, _request):
+    """Describes a service. Used by config service to discover other services.
+    """
+    meta = MetadataResponseMessage(version=METADATA_FORMAT_VERSION)
+    http_headers = dict(self.request_state.headers)
+    assert 'host' in http_headers, http_headers
+    meta.validation = meta.Validator(
+        url='https://{hostname}/_ah/api/{name}/{version}/{path}validate'.format(
+            hostname=http_headers['host'],
+            name=self.api_info.name,
+            version=self.api_info.version,
+            path=self.api_info.path or '',
+        )
+    )
+    for p in sorted(get_default_rule_set().patterns()):
+      meta.validation.patterns.append(ConfigPattern(**p._asdict()))
+    return meta