Add LogDog Python client library.

client/libs/logdog/bootstrap.py

Index: client/libs/logdog/bootstrap.py
diff --git a/client/libs/logdog/bootstrap.py b/client/libs/logdog/bootstrap.py
new file mode 100644
index 0000000000000000000000000000000000000000..980368babb02709b70f5b63c7e07bcd64a7ebb7f
--- /dev/null
+++ b/client/libs/logdog/bootstrap.py
@@ -0,0 +1,72 @@
+# Copyright 2016 The LUCI 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.
+
+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'))
+
+
+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'
+
+  @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,))
+
+    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))
+
+  def stream_client(self):
+    """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.
+
+    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.StreamClient.create(self.streamserver_uri)