Update LogDog client library to generate URLs.

client/libs/logdog/bootstrap.py

 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import collections
 import os
 
 from libs.logdog import stream, streamname
 
 
 class NotBootstrappedError(RuntimeError):
   """Raised when the current environment is missing Butler bootstrap variables.
   """
 
 
 _ButlerBootstrapBase = collections.namedtuple('_ButlerBootstrapBase',
-    ('project', 'prefix', 'streamserver_uri'))
+    ('project', 'prefix', 'streamserver_uri', 'coordinator_host'))
 
 
 class ButlerBootstrap(_ButlerBootstrapBase):
   """Loads LogDog Butler bootstrap parameters from the environment.
 
   LogDog Butler adds variables describing the LogDog stream parameters to the
   environment when it bootstraps an application. This class probes the
   environment and identifies those parameters.
   """
 
   _ENV_PROJECT = 'LOGDOG_STREAM_PROJECT'
   _ENV_PREFIX = 'LOGDOG_STREAM_PREFIX'
   _ENV_STREAM_SERVER_PATH = 'LOGDOG_STREAM_SERVER_PATH'
+  _ENV_COORDINATOR_HOST = 'LOGDOG_COORDINATOR_HOST'
 
   @classmethod
   def probe(cls, env=None):
     """Returns (ButlerBootstrap): The probed bootstrap environment.
 
     Args:
       env (dict): The environment to probe. If None, `os.getenv` will be used.
 
     Raises:
       NotBootstrappedError if the current environment is not boostrapped.
     """
     if env is None:
       env = os.environ
+
     project = env.get(cls._ENV_PROJECT)
-    prefix = env.get(cls._ENV_PREFIX)
-
     if not project:
       raise NotBootstrappedError('Missing project [%s]' % (cls._ENV_PROJECT,))
 
+    prefix = env.get(cls._ENV_PREFIX)
     if not prefix:
       raise NotBootstrappedError('Missing prefix [%s]' % (cls._ENV_PREFIX,))
     try:
       streamname.validate_stream_name(prefix)
     except ValueError as e:
       raise NotBootstrappedError('Prefix (%s) is invalid: %s' % (prefix, e))
 
-    return cls(project=project, prefix=prefix,
-               streamserver_uri=env.get(cls._ENV_STREAM_SERVER_PATH))
+    return cls(
+        project=project,
+        prefix=prefix,
+        streamserver_uri=env.get(cls._ENV_STREAM_SERVER_PATH),
+        coordinator_host=env.get(cls._ENV_COORDINATOR_HOST))
 
-  def stream_client(self):
+  def stream_client(self, reg=None):
     """Returns: (StreamClient) stream client for the bootstrap streamserver URI.
 
     If the Butler accepts external stream connections, it will export a
     streamserver URI in the environment. This will create a StreamClient
     instance to operate on the streamserver if one is defined.
 
+    Args:
+      reg (stream.StreamProtocolRegistry or None): The stream protocol registry
+          to use to create the stream. If None, the default global registry will
+          be used (recommended).
+
     Raises:
       ValueError: If no streamserver URI is present in the environment.
     """
     if not self.streamserver_uri:
       raise ValueError('No streamserver in bootstrap environment.')
-    return stream.create(self.streamserver_uri)
+    reg = reg or stream._default_registry
+    return reg.create(
+        self.streamserver_uri,
+        project=self.project,
+        prefix=self.prefix,
+        coordinator_host=self.coordinator_host)