Repository: kubernetes-incubator/client-python (python)

Issue:
Support kube-config change context
Right now the load kube config function loads the default context. We should support loading other contexts and [maybe?] listing them.

Pull request description:
Kube config loader improvement
Current implementation of kube config loader, loads the default contexts. In this PR, it changed to load any context or list contexts. Also the code is refactored for better testability. kube config loader tests also added.

fixes #46

Patch:
diff --git a/examples/example4.py b/examples/example4.py
new file mode 100644
index 000000000..af309b191
--- /dev/null
+++ b/examples/example4.py
@@ -0,0 +1,62 @@
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+from kubernetes import client, config
+from kubernetes.client import configuration
+
+
+def main():
+    config_file = os.path.join(os.path.expanduser('~'), '.kube', 'config')
+    contexts, active_context = config.list_kube_config_contexts(config_file)
+    if not contexts:
+        print("Cannot find any context in kube-config file.")
+        return
+    contexts = [context['name'] for context in contexts]
+    active_context = active_context['name']
+    for i, context in enumerate(contexts):
+        format_str = "%d. %s"
+        if context == active_context:
+            format_str = "* " + format_str
+        print(format_str % (i, context))
+    context = input("Enter context number: ")
+    context = int(context)
+    if context not in range(len(contexts)):
+        print(
+            "Number out of range. Using default context %s." %
+            active_context)
+        context_name = active_context
+    else:
+        context_name = contexts[context]
+
+    # Configs can be set in Configuration class directly or using helper
+    # utility
+    config.load_kube_config(config_file, context_name)
+
+    print("Active host is %s" % configuration.host)
+
+    v1 = client.CoreV1Api()
+    print("Listing pods with their IPs:")
+    ret = v1.list_pod_for_all_namespaces(watch=False)
+    for item in ret.items:
+        print(
+            "%s\t%s\t%s" %
+            (item.status.pod_ip,
+             item.metadata.namespace,
+             item.metadata.name))
+
+
+if __name__ == '__main__':
+    main()
diff --git a/kubernetes/config/__init__.py b/kubernetes/config/__init__.py
index 9254c408b..92632043c 100644
--- a/kubernetes/config/__init__.py
+++ b/kubernetes/config/__init__.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from .kube_config import load_kube_config
+from .config_exception import ConfigException
 from .incluster_config import load_incluster_config
-from .incluster_config import ConfigException
+from .kube_config import list_kube_config_contexts
+from .kube_config import load_kube_config
diff --git a/kubernetes/config/config_exception.py b/kubernetes/config/config_exception.py
new file mode 100644
index 000000000..23fab022c
--- /dev/null
+++ b/kubernetes/config/config_exception.py
@@ -0,0 +1,17 @@
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class ConfigException(Exception):
+    pass
diff --git a/kubernetes/config/incluster_config.py b/kubernetes/config/incluster_config.py
index b4cc3c99d..3ba1113f1 100644
--- a/kubernetes/config/incluster_config.py
+++ b/kubernetes/config/incluster_config.py
@@ -16,10 +16,12 @@ import os
 
 from kubernetes.client import configuration
 
-_SERVICE_HOST_ENV_NAME = "KUBERNETES_SERVICE_HOST"
-_SERVICE_PORT_ENV_NAME = "KUBERNETES_SERVICE_PORT"
-_SERVICE_TOKEN_FILENAME = "/var/run/secrets/kubernetes.io/serviceaccount/token"
-_SERVICE_CERT_FILENAME = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
+from .config_exception import ConfigException
+
+SERVICE_HOST_ENV_NAME = "KUBERNETES_SERVICE_HOST"
+SERVICE_PORT_ENV_NAME = "KUBERNETES_SERVICE_PORT"
+SERVICE_TOKEN_FILENAME = "/var/run/secrets/kubernetes.io/serviceaccount/token"
+SERVICE_CERT_FILENAME = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
 
 
 def _join_host_port(host, port):
@@ -31,16 +33,10 @@ def _join_host_port(host, port):
     return template % (host, port)
 
 
-class ConfigException(Exception):
-    pass
-
-
 class InClusterConfigLoader(object):
 
-    def __init__(self, host_env_name, port_env_name, token_filename,
+    def __init__(self, token_filename,
                  cert_filename, environ=os.environ):
-        self._host_env_name = host_env_name
-        self._port_env_name = port_env_name
         self._token_filename = token_filename
         self._cert_filename = cert_filename
         self._environ = environ
@@ -50,24 +46,34 @@ class InClusterConfigLoader(object):
         self._set_config()
 
     def _load_config(self):
-        if (self._host_env_name not in self._environ or
-                self._port_env_name not in self._environ):
+        if (SERVICE_HOST_ENV_NAME not in self._environ or
+                SERVICE_PORT_ENV_NAME not in self._environ):
             raise ConfigException("Service host/port is not set.")
 
+        if (not self._environ[SERVICE_HOST_ENV_NAME] or
+                not self._environ[SERVICE_PORT_ENV_NAME]):
+            raise ConfigException("Service host/port is set but empty.")
+
         self.host = (
-            "https://" + _join_host_port(self._environ[self._host_env_name],
-                                         self._environ[self._port_env_name]))
+            "https://" + _join_host_port(self._environ[SERVICE_HOST_ENV_NAME],
+                                         self._environ[SERVICE_PORT_ENV_NAME]))
 
         if not os.path.isfile(self._token_filename):
             raise ConfigException("Service token file does not exists.")
 
         with open(self._token_filename) as f:
             self.token = f.read()
+            if not self.token:
+                raise ConfigException("Token file exists but empty.")
 
         if not os.path.isfile(self._cert_filename):
             raise ConfigException(
                 "Service certification file does not exists.")
 
+        with open(self._cert_filename) as f:
+            if not f.read():
+                raise ConfigException("Cert file exists but empty.")
+
         self.ssl_ca_cert = self._cert_filename
 
     def _set_config(self):
@@ -81,7 +87,5 @@ def load_incluster_config():
     cluster. It's intended for clients that expect to be running inside a pod
     running on kubernetes. It will raise an exception if called from a process
     not running in a kubernetes environment."""
-    InClusterConfigLoader(host_env_name=_SERVICE_HOST_ENV_NAME,
-                          port_env_name=_SERVICE_PORT_ENV_NAME,
-                          token_filename=_SERVICE_TOKEN_FILENAME,
-                          cert_filename=_SERVICE_CERT_FILENAME).load_and_set()
+    InClusterConfigLoader(token_filename=SERVICE_TOKEN_FILENAME,
+                          cert_filename=SERVICE_CERT_FILENAME).load_and_set()
diff --git a/kubernetes/config/kube_config.py b/kubernetes/config/kube_config.py
index cc1c483de..e7e593aa1 100644
--- a/kubernetes/config/kube_config.py
+++ b/kubernetes/config/kube_config.py
@@ -22,151 +22,243 @@ import yaml
 from kubernetes.client import configuration
 from oauth2client.client import GoogleCredentials
 
-_temp_files = []
+from .config_exception import ConfigException
+
+_temp_files = {}
 
 
 def _cleanup_temp_files():
-    for f in _temp_files:
-        os.remove(f)
+    for temp_file in _temp_files.values():
+        os.remove(temp_file)
 
 
 def _create_temp_file_with_content(content):
     if len(_temp_files) == 0:
         atexit.register(_cleanup_temp_files)
+    # Because we may change context several times, try to remember files we
+    # created and reuse them at a small memory cost.
+    content_key = str(content)
+    if content_key in _temp_files:
+        return _temp_files[content_key]
     _, name = tempfile.mkstemp()
-    _temp_files.append(name)
-    if isinstance(content, str):
-        content = content.encode('utf8')
+    _temp_files[content_key] = name
     with open(name, 'wb') as fd:
-        fd.write(base64.decodestring(content))
+        fd.write(content.encode() if isinstance(content, str) else content)
     return name
 
 
-def _file_from_file_or_data(o, file_key_name, data_key_name=None):
-    if not data_key_name:
-        data_key_name = file_key_name + "-data"
-    if data_key_name in o:
-        return _create_temp_file_with_content(o[data_key_name])
-    if file_key_name in o:
-        return o[file_key_name]
-
-
-def _data_from_file_or_data(o, file_key_name, data_key_name=None):
-    if not data_key_name:
-        data_key_name = file_key_name + "_data"
-    if data_key_name in o:
-        return o[data_key_name]
-    if file_key_name in o:
-        with open(o[file_key_name], 'r') as f:
-            data = f.read()
-        return data
-
-
-def _load_gcp_token(user):
-    if 'auth-provider' not in user:
-        return
-    if 'name' not in user['auth-provider']:
-        return
-    if user['auth-provider']['name'] != 'gcp':
-        return
-    # Ignore configs in auth-provider and rely on GoogleCredentials
-    # caching and refresh mechanism.
-    # TODO: support gcp command based token ("cmd-path" config).
-    return (GoogleCredentials
-            .get_application_default()
-            .get_access_token()
-            .access_token)
-
-
-def _load_authentication(user):
-    """Read authentication from kube-config user section.
-
-    This function goes through various authetication methods in user section of
-    kubeconfig and stops if it founds a valid authentication method. The order
-    of authentication methods is:
-
-        1. GCP auth-provider
-        2. token_data
-        3. token field (point to a token file)
-        4. username/password
-    """
-    # Read authentication
-    token = _load_gcp_token(user)
-    if not token:
-        token = _data_from_file_or_data(user, 'tokenFile', 'token')
-    if token:
-        configuration.api_key['authorization'] = "bearer " + token
-    else:
-        if 'username' in user and 'password' in user:
-            configuration.api_key['authorization'] = urllib3.util.make_headers(
-                basic_auth=user['username'] + ':' +
-                user['password']).get('authorization')
-
-
-def _load_cluster_info(cluster, user):
-    """Loads cluster information from kubeconfig such as host and SSL certs."""
-    if 'server' in cluster:
-        configuration.host = cluster['server']
-        if configuration.host.startswith("https"):
-            configuration.ssl_ca_cert = _file_from_file_or_data(
-                cluster, 'certificate-authority')
-            configuration.cert_file = _file_from_file_or_data(
-                user, 'client-certificate')
-            configuration.key_file = _file_from_file_or_data(
-                user, 'client-key')
-
-
-class _node:
-    """Remembers each key's path and construct a relevant exception message
-    in case of missing keys."""
+class FileOrData(object):
+    """Utility class to read content of obj[%data_key_name] or file's
+     content of obj[%file_key_name] and represent it as file or data.
+     Note that the data is preferred. The obj[%file_key_name] will be used iff
+     obj['%data_key_name'] is not set or empty. Assumption is file content is
+     raw data and data field is base64 string."""
+
+    def __init__(self, obj, file_key_name, data_key_name=None):
+        if not data_key_name:
+            data_key_name = file_key_name + "-data"
+        self._file = None
+        self._data = None
+        if data_key_name in obj:
+            self._data = obj[data_key_name]
+        elif file_key_name in obj:
+            self._file = obj[file_key_name]
+
+    def as_file(self):
+        """If obj[%data_key_name] exists, return name of a file with base64
+        decoded obj[%data_key_name] content otherwise obj[%file_key_name]."""
+        use_data_if_no_file = not self._file and self._data
+        if use_data_if_no_file:
+            self._file = _create_temp_file_with_content(
+                base64.decodestring(self._data.encode()))
+        return self._file
+
+    def as_data(self):
+        """If obj[%data_key_name] exists, Return obj[%data_key_name] otherwise
+        base64 encoded string of obj[%file_key_name] file content."""
+        use_file_if_no_data = not self._data and self._file
+        if use_file_if_no_data:
+            with open(self._file) as f:
+                self._data = bytes.decode(
+                    base64.encodestring(str.encode(f.read())))
+        return self._data
+
+
+class KubeConfigLoader(object):
+
+    def __init__(self, config_dict, active_context=None,
+                 get_google_credentials=None, client_configuration=None):
+        self._config = ConfigNode('kube-config', config_dict)
+        self._current_context = None
+        self._user = None
+        self._cluster = None
+        self.set_active_context(active_context)
+        if get_google_credentials:
+            self._get_google_credentials = get_google_credentials
+        else:
+            self._get_google_credentials = lambda: (
+                GoogleCredentials.get_application_default()
+                .get_access_token().access_token)
+        if client_configuration:
+            self._client_configuration = client_configuration
+        else:
+            self._client_configuration = configuration
+
+    def set_active_context(self, context_name=None):
+        if context_name is None:
+            context_name = self._config['current-context']
+        self._current_context = self._config['contexts'].get_with_name(
+            context_name)
+        if self._current_context['context'].safe_get('user'):
+            self._user = self._config['users'].get_with_name(
+                self._current_context['context']['user'])['user']
+        else:
+            self._user = None
+        self._cluster = self._config['clusters'].get_with_name(
+            self._current_context['context']['cluster'])['cluster']
+
+    def _load_authentication(self):
+        """Read authentication from kube-config user section if exists.
+
+        This function goes through various authentication methods in user
+        section of kube-config and stops if it finds a valid authentication
+        method. The order of authentication methods is:
+
+            1. GCP auth-provider
+            2. token_data
+            3. token field (point to a token file)
+            4. username/password
+        """
+        if not self._user:
+            return
+        if self._load_gcp_token():
+            return
+        if self._load_user_token():
+            return
+        self._load_user_pass_token()
+
+    def _load_gcp_token(self):
+        if 'auth-provider' not in self._user:
+            return
+        if 'name' not in self._user['auth-provider']:
+            return
+        if self._user['auth-provider']['name'] != 'gcp':
+            return
+        # Ignore configs in auth-provider and rely on GoogleCredentials
+        # caching and refresh mechanism.
+        # TODO: support gcp command based token ("cmd-path" config).
+        self.token = self._get_google_credentials()
+        return self.token
+
+    def _load_user_token(self):
+        token = FileOrData(self._user, 'tokenFile', 'token').as_data()
+        if token:
+            self.token = token
+            return True
+
+    def _load_user_pass_token(self):
+        if 'username' in self._user and 'password' in self._user:
+            self.token = urllib3.util.make_headers(
+                basic_auth=(self._user['username'] + ':' +
+                            self._user['password'])).get('authorization')
+            return True
+
+    def _load_cluster_info(self):
+        if 'server' in self._cluster:
+            self.host = self._cluster['server']
+            if self.host.startswith("https"):
+                self.ssl_ca_cert = FileOrData(
+                    self._cluster, 'certificate-authority').as_file()
+                self.cert_file = FileOrData(
+                    self._user, 'client-certificate').as_file()
+                self.key_file = FileOrData(self._user, 'client-key').as_file()
+
+    def _set_config(self):
+        if 'token' in self.__dict__:
+            self._client_configuration.api_key['authorization'] = self.token
+        # copy these keys directly from self to configuration object
+        keys = ['host', 'ssl_ca_cert', 'cert_file', 'key_file']
+        for key in keys:
+            if key in self.__dict__:
+                setattr(self._client_configuration, key, getattr(self, key))
+
+    def load_and_set(self):
+        self._load_authentication()
+        self._load_cluster_info()
+        self._set_config()
+
+    def list_contexts(self):
+        return [context.value for context in self._config['contexts']]
+
+    @property
+    def current_context(self):
+        return self._current_context.value
+
+
+class ConfigNode(object):
+    """Remembers each config key's path and construct a relevant exception
+    message in case of missing keys. The assumption is all access keys are
+    present in a well-formed kube-config."""
 
     def __init__(self, name, value):
-        self._name = name
-        self._value = value
+        self.name = name
+        self.value = value
 
     def __contains__(self, key):
-        return key in self._value
+        return key in self.value
+
+    def __len__(self):
+        return len(self.value)
+
+    def safe_get(self, key):
+        if (isinstance(self.value, list) and isinstance(key, int) or
+                key in self.value):
+            return self.value[key]
 
     def __getitem__(self, key):
-        if key in self._value:
-            v = self._value[key]
-            if isinstance(v, dict) or isinstance(v, list):
-                return _node('%s/%s' % (self._name, key), v)
-            else:
-                return v
-        raise Exception(
-            'Invalid kube-config file. Expected key %s in %s'
-            % (key, self._name))
+        v = self.safe_get(key)
+        if not v:
+            raise ConfigException(
+                'Invalid kube-config file. Expected key %s in %s'
+                % (key, self.name))
+        if isinstance(v, dict) or isinstance(v, list):
+            return ConfigNode('%s/%s' % (self.name, key), v)
+        else:
+            return v
 
     def get_with_name(self, name):
-        if not isinstance(self._value, list):
-            raise Exception(
+        if not isinstance(self.value, list):
+            raise ConfigException(
                 'Invalid kube-config file. Expected %s to be a list'
-                % self._name)
-        for v in self._value:
+                % self.name)
+        for v in self.value:
             if 'name' not in v:
-                raise Exception(
+                raise ConfigException(
                     'Invalid kube-config file. '
                     'Expected all values in %s list to have \'name\' key'
-                    % self._name)
+                    % self.name)
             if v['name'] == name:
-                return _node('%s[name=%s]' % (self._name, name), v)
-        raise Exception(
-            "Cannot find object with name %s in %s list" % (name, self._name))
+                return ConfigNode('%s[name=%s]' % (self.name, name), v)
+        raise ConfigException(
+            'Invalid kube-config file. '
+            'Expected object with name %s in %s list' % (name, self.name))
 
 
-def load_kube_config(config_file):
-    """Loads authentication and cluster information from kube-config file
-    and store them in kubernetes.client.configuration."""
-
+def list_kube_config_contexts(config_file):
     with open(config_file) as f:
-        config = _node('kube-config', yaml.load(f))
+        loader = KubeConfigLoader(config_dict=yaml.load(f))
+    return loader.list_contexts(), loader.current_context
 
-        current_context = config['contexts'].get_with_name(
-            config['current-context'])['context']
-        user = config['users'].get_with_name(current_context['user'])['user']
-        cluster = config['clusters'].get_with_name(
-            current_context['cluster'])['cluster']
 
-        _load_cluster_info(cluster, user)
-        _load_authentication(user)
+def load_kube_config(config_file, context=None):
+    """Loads authentication and cluster information from kube-config file
+    and stores them in kubernetes.client.configuration.
+
+    :param config_file: Name of the kube-config file.
+    :param context: set the active context. If is set to None, current_context
+    from config file will be used.
+    """
+
+    with open(config_file) as f:
+        KubeConfigLoader(
+            config_dict=yaml.load(f), active_context=context).load_and_set()


Test patch:
diff --git a/kubernetes/config/incluster_config_test.py b/kubernetes/config/incluster_config_test.py
index 7f7405e4f..622b31b37 100644
--- a/kubernetes/config/incluster_config_test.py
+++ b/kubernetes/config/incluster_config_test.py
@@ -16,19 +16,22 @@ import os
 import tempfile
 import unittest
 
-from kubernetes.client import configuration
-
-from .incluster_config import (_SERVICE_HOST_ENV_NAME, _SERVICE_PORT_ENV_NAME,
-                               ConfigException, InClusterConfigLoader)
+from .config_exception import ConfigException
+from .incluster_config import (SERVICE_HOST_ENV_NAME, SERVICE_PORT_ENV_NAME,
+                               InClusterConfigLoader, _join_host_port)
 
 _TEST_TOKEN = "temp_token"
+_TEST_CERT = "temp_cert"
 _TEST_HOST = "127.0.0.1"
-_TEST_IPV6_HOST = "::1"
 _TEST_PORT = "80"
-_TEST_ENVIRON = {_SERVICE_HOST_ENV_NAME: _TEST_HOST,
-                 _SERVICE_PORT_ENV_NAME: _TEST_PORT}
-_TEST_IPV6_ENVIRON = {_SERVICE_HOST_ENV_NAME: _TEST_IPV6_HOST,
-                      _SERVICE_PORT_ENV_NAME: _TEST_PORT}
+_TEST_HOST_PORT = "127.0.0.1:80"
+_TEST_IPV6_HOST = "::1"
+_TEST_IPV6_HOST_PORT = "[::1]:80"
+
+_TEST_ENVIRON = {SERVICE_HOST_ENV_NAME: _TEST_HOST,
+                 SERVICE_PORT_ENV_NAME: _TEST_PORT}
+_TEST_IPV6_ENVIRON = {SERVICE_HOST_ENV_NAME: _TEST_IPV6_HOST,
+                      SERVICE_PORT_ENV_NAME: _TEST_PORT}
 
 
 class InClusterConfigTest(unittest.TestCase):
@@ -49,38 +52,29 @@ class InClusterConfigTest(unittest.TestCase):
 
     def get_test_loader(
             self,
-            host_env_name=_SERVICE_HOST_ENV_NAME,
-            port_env_name=_SERVICE_PORT_ENV_NAME,
             token_filename=None,
             cert_filename=None,
             environ=_TEST_ENVIRON):
         if not token_filename:
             token_filename = self._create_file_with_temp_content(_TEST_TOKEN)
         if not cert_filename:
-            cert_filename = self._create_file_with_temp_content()
+            cert_filename = self._create_file_with_temp_content(_TEST_CERT)
         return InClusterConfigLoader(
-            host_env_name=host_env_name,
-            port_env_name=port_env_name,
             token_filename=token_filename,
             cert_filename=cert_filename,
             environ=environ)
 
+    def test_join_host_port(self):
+        self.assertEqual(_TEST_HOST_PORT,
+                         _join_host_port(_TEST_HOST, _TEST_PORT))
+        self.assertEqual(_TEST_IPV6_HOST_PORT,
+                         _join_host_port(_TEST_IPV6_HOST, _TEST_PORT))
+
     def test_load_config(self):
-        cert_filename = self._create_file_with_temp_content()
+        cert_filename = self._create_file_with_temp_content(_TEST_CERT)
         loader = self.get_test_loader(cert_filename=cert_filename)
         loader._load_config()
-        self.assertEqual("https://%s:%s" % (_TEST_HOST, _TEST_PORT),
-                         loader.host)
-        self.assertEqual(cert_filename, loader.ssl_ca_cert)
-        self.assertEqual(_TEST_TOKEN, loader.token)
-
-    def test_load_config_with_bracketed_hostname(self):
-        cert_filename = self._create_file_with_temp_content()
-        loader = self.get_test_loader(cert_filename=cert_filename,
-                                      environ=_TEST_IPV6_ENVIRON)
-        loader._load_config()
-        self.assertEqual("https://[%s]:%s" % (_TEST_IPV6_HOST, _TEST_PORT),
-                         loader.host)
+        self.assertEqual("https://" + _TEST_HOST_PORT, loader.host)
         self.assertEqual(cert_filename, loader.ssl_ca_cert)
         self.assertEqual(_TEST_TOKEN, loader.token)
 
@@ -93,21 +87,45 @@ class InClusterConfigTest(unittest.TestCase):
             pass
 
     def test_no_port(self):
-        loader = self.get_test_loader(port_env_name="not_exists_port")
+        loader = self.get_test_loader(
+            environ={SERVICE_HOST_ENV_NAME: _TEST_HOST})
         self._should_fail_load(loader, "no port specified")
 
+    def test_empty_port(self):
+        loader = self.get_test_loader(
+            environ={SERVICE_HOST_ENV_NAME: _TEST_HOST,
+                     SERVICE_PORT_ENV_NAME: ""})
+        self._should_fail_load(loader, "empty port specified")
+
     def test_no_host(self):
-        loader = self.get_test_loader(host_env_name="not_exists_host")
+        loader = self.get_test_loader(
+            environ={SERVICE_PORT_ENV_NAME: _TEST_PORT})
         self._should_fail_load(loader, "no host specified")
 
+    def test_empty_host(self):
+        loader = self.get_test_loader(
+            environ={SERVICE_HOST_ENV_NAME: "",
+                     SERVICE_PORT_ENV_NAME: _TEST_PORT})
+        self._should_fail_load(loader, "empty host specified")
+
     def test_no_cert_file(self):
         loader = self.get_test_loader(cert_filename="not_exists_file_1123")
         self._should_fail_load(loader, "cert file does not exists")
 
+    def test_empty_cert_file(self):
+        loader = self.get_test_loader(
+            cert_filename=self._create_file_with_temp_content())
+        self._should_fail_load(loader, "empty cert file provided")
+
     def test_no_token_file(self):
         loader = self.get_test_loader(token_filename="not_exists_file_1123")
         self._should_fail_load(loader, "token file does not exists")
 
+    def test_empty_token_file(self):
+        loader = self.get_test_loader(
+            token_filename=self._create_file_with_temp_content())
+        self._should_fail_load(loader, "empty token file provided")
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/kubernetes/config/kube_config_test.py b/kubernetes/config/kube_config_test.py
new file mode 100644
index 000000000..6c4cd2430
--- /dev/null
+++ b/kubernetes/config/kube_config_test.py
@@ -0,0 +1,469 @@
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import base64
+import os
+import tempfile
+import unittest
+
+from .config_exception import ConfigException
+from .kube_config import (ConfigNode, FileOrData, KubeConfigLoader,
+                          _create_temp_file_with_content)
+
+
+def _base64(string):
+    return base64.encodestring(string.encode()).decode()
+
+
+TEST_FILE_KEY = "file"
+TEST_DATA_KEY = "data"
+TEST_FILENAME = "test-filename"
+
+TEST_DATA = "test-data"
+TEST_DATA_BASE64 = _base64(TEST_DATA)
+
+TEST_ANOTHER_DATA = "another-test-data"
+TEST_ANOTHER_DATA_BASE64 = _base64(TEST_ANOTHER_DATA)
+
+TEST_HOST = "test-host"
+TEST_USERNAME = "me"
+TEST_PASSWORD = "pass"
+# token for me:pass
+TEST_BASIC_TOKEN = "Basic bWU6cGFzcw=="
+
+TEST_SSL_HOST = "https://test-host"
+TEST_CERTIFICATE_AUTH = "cert-auth"
+TEST_CERTIFICATE_AUTH_BASE64 = _base64(TEST_CERTIFICATE_AUTH)
+TEST_CLIENT_KEY = "client-key"
+TEST_CLIENT_KEY_BASE64 = _base64(TEST_CLIENT_KEY)
+TEST_CLIENT_CERT = "client-cert"
+TEST_CLIENT_CERT_BASE64 = _base64(TEST_CLIENT_CERT)
+
+
+class BaseTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self._temp_files = []
+
+    def tearDown(self):
+        for f in self._temp_files:
+            os.remove(f)
+
+    def _create_temp_file(self, content=""):
+        handler, name = tempfile.mkstemp()
+        self._temp_files.append(name)
+        os.write(handler, str.encode(content))
+        os.close(handler)
+        return name
+
+
+class TestFileOrData(BaseTestCase):
+
+    @staticmethod
+    def get_file_content(filename):
+        with open(filename) as f:
+            return f.read()
+
+    def test_file_given_file(self):
+        obj = {TEST_FILE_KEY: TEST_FILENAME}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY)
+        self.assertEqual(TEST_FILENAME, t.as_file())
+
+    def test_file_given_data(self):
+        obj = {TEST_DATA_KEY: TEST_DATA_BASE64}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY,
+                       data_key_name=TEST_DATA_KEY)
+        self.assertEqual(TEST_DATA, self.get_file_content(t.as_file()))
+
+    def test_data_given_data(self):
+        obj = {TEST_DATA_KEY: TEST_DATA_BASE64}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY,
+                       data_key_name=TEST_DATA_KEY)
+        self.assertEqual(TEST_DATA_BASE64, t.as_data())
+
+    def test_data_given_file(self):
+        obj = {
+            TEST_FILE_KEY: self._create_temp_file(content=TEST_DATA)}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY)
+        self.assertEqual(TEST_DATA_BASE64, t.as_data())
+
+    def test_data_given_file_and_data(self):
+        obj = {
+            TEST_DATA_KEY: TEST_DATA_BASE64,
+            TEST_FILE_KEY: self._create_temp_file(
+                content=TEST_ANOTHER_DATA)}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY,
+                       data_key_name=TEST_DATA_KEY)
+        self.assertEqual(TEST_DATA_BASE64, t.as_data())
+
+    def test_file_given_file_and_data(self):
+        obj = {
+            TEST_DATA_KEY: TEST_DATA_BASE64,
+            TEST_FILE_KEY: self._create_temp_file(
+                content=TEST_ANOTHER_DATA)}
+        t = FileOrData(obj=obj, file_key_name=TEST_FILE_KEY,
+                       data_key_name=TEST_DATA_KEY)
+        self.assertEqual(TEST_DATA, self.get_file_content(t.as_file()))
+
+    def test_create_temp_file_with_content(self):
+        self.assertEqual(TEST_DATA,
+                         self.get_file_content(
+                             _create_temp_file_with_content(TEST_DATA)))
+
+
+class TestConfigNode(BaseTestCase):
+
+    test_obj = {"key1": "test", "key2": ["a", "b", "c"],
+                "key3": {"inner_key": "inner_value"},
+                "with_names": [{"name": "test_name", "value": "test_value"},
+                               {"name": "test_name2",
+                                "value": {"key1", "test"}},
+                               {"name": "test_name3", "value": [1, 2, 3]}]}
+
+    def setUp(self):
+        super(TestConfigNode, self).setUp()
+        self.node = ConfigNode("test_obj", self.test_obj)
+
+    def test_normal_map_array_operations(self):
+        self.assertEqual("test", self.node['key1'])
+        self.assertEqual(4, len(self.node))
+
+        self.assertEqual("test_obj/key2", self.node['key2'].name)
+        self.assertEqual(["a", "b", "c"], self.node['key2'].value)
+        self.assertEqual("b", self.node['key2'][1])
+        self.assertEqual(3, len(self.node['key2']))
+
+        self.assertEqual("test_obj/key3", self.node['key3'].name)
+        self.assertEqual({"inner_key": "inner_value"}, self.node['key3'].value)
+        self.assertEqual("inner_value", self.node['key3']["inner_key"])
+        self.assertEqual(1, len(self.node['key3']))
+
+    def test_get_with_name(self):
+        node = self.node["with_names"]
+        self.assertEqual(
+            "test_value",
+            node.get_with_name("test_name")["value"])
+        self.assertTrue(
+            isinstance(node.get_with_name("test_name2"), ConfigNode))
+        self.assertTrue(
+            isinstance(node.get_with_name("test_name3"), ConfigNode))
+        self.assertEqual("test_obj/with_names[name=test_name2]",
+                         node.get_with_name("test_name2").name)
+        self.assertEqual("test_obj/with_names[name=test_name3]",
+                         node.get_with_name("test_name3").name)
+
+    def expect_exception(self, func, message_part):
+        with self.assertRaises(ConfigException) as context:
+            func()
+        self.assertIn(message_part, str(context.exception))
+
+    def test_key_does_not_exists(self):
+        self.expect_exception(lambda: self.node['not-exists-key'],
+                              "Expected key not-exists-key in test_obj")
+        self.expect_exception(lambda: self.node['key3']['not-exists-key'],
+                              "Expected key not-exists-key in test_obj/key3")
+
+    def test_get_with_name_on_invalid_object(self):
+        self.expect_exception(
+            lambda: self.node['key2'].get_with_name('no-name'),
+            "Expected all values in test_obj/key2 list to have \'name\' key")
+
+    def test_get_with_name_on_non_list_object(self):
+        self.expect_exception(
+            lambda: self.node['key3'].get_with_name('no-name'),
+            "Expected test_obj/key3 to be a list")
+
+    def test_get_with_name_on_name_does_not_exists(self):
+        self.expect_exception(
+            lambda: self.node['with_names'].get_with_name('no-name'),
+            "Expected object with name no-name in test_obj/with_names list")
+
+
+class FakeConfig:
+
+    FILE_KEYS = ["ssl_ca_cert", "key_file", "cert_file"]
+
+    def __init__(self, token=None, **kwargs):
+        self.api_key = {}
+        if token:
+            self.api_key['authorization'] = token
+
+        self.__dict__.update(kwargs)
+
+    def __eq__(self, other):
+        if len(self.__dict__) != len(other.__dict__):
+            return
+        for k, v in self.__dict__.items():
+            if k not in other.__dict__:
+                return
+            if k in self.FILE_KEYS:
+                try:
+                    with open(v) as f1, open(other.__dict__[k]) as f2:
+                        if f1.read() != f2.read():
+                            return
+                except IOError:
+                    # fall back to only compare filenames in case we are
+                    # testing the passing of filenames to the config
+                    if other.__dict__[k] != v:
+                        return
+            else:
+                if other.__dict__[k] != v:
+                    return
+        return True
+
+    def __repr__(self):
+        rep = "\n"
+        for k, v in self.__dict__.items():
+            val = v
+            if k in self.FILE_KEYS:
+                try:
+                    with open(v) as f:
+                        val = "FILE: %s" % str.decode(f.read())
+                except IOError as e:
+                    val = "ERROR: %s" % str(e)
+            rep += "\t%s: %s\n" % (k, val)
+        return "Config(%s\n)" % rep
+
+
+class TestKubeConfigLoader(BaseTestCase):
+    TEST_KUBE_CONFIG = {
+        "current-context": "no_user",
+        "contexts": [
+            {
+                "name": "no_user",
+                "context": {
+                    "cluster": "default"
+                }
+            },
+            {
+                "name": "simple_token",
+                "context": {
+                    "cluster": "default",
+                    "user": "simple_token"
+                }
+            },
+            {
+                "name": "gcp",
+                "context": {
+                    "cluster": "default",
+                    "user": "gcp"
+                }
+            },
+            {
+                "name": "user_pass",
+                "context": {
+                    "cluster": "default",
+                    "user": "user_pass"
+                }
+            },
+            {
+                "name": "ssl",
+                "context": {
+                    "cluster": "ssl",
+                    "user": "ssl"
+                }
+            },
+            {
+                "name": "ssl-no_file",
+                "context": {
+                    "cluster": "ssl-no_file",
+                    "user": "ssl-no_file"
+                }
+            },
+        ],
+        "clusters": [
+            {
+                "name": "default",
+                "cluster": {
+                    "server": TEST_HOST
+                }
+            },
+            {
+                "name": "ssl-no_file",
+                "cluster": {
+                    "server": TEST_SSL_HOST,
+                    "certificate-authority": TEST_CERTIFICATE_AUTH,
+                }
+            },
+            {
+                "name": "ssl",
+                "cluster": {
+                    "server": TEST_SSL_HOST,
+                    "certificate-authority-data": TEST_CERTIFICATE_AUTH_BASE64,
+                }
+            },
+        ],
+        "users": [
+            {
+                "name": "simple_token",
+                "user": {
+                    "token": TEST_DATA_BASE64,
+                    "username": TEST_USERNAME,  # should be ignored
+                    "password": TEST_PASSWORD,  # should be ignored
+                }
+            },
+            {
+                "name": "gcp",
+                "user": {
+                    "auth-provider": {
+                        "name": "gcp",
+                        "access_token": "not_used",
+                    },
+                    "token": TEST_DATA_BASE64,  # should be ignored
+                    "username": TEST_USERNAME,  # should be ignored
+                    "password": TEST_PASSWORD,  # should be ignored
+                }
+            },
+            {
+                "name": "user_pass",
+                "user": {
+                    "username": TEST_USERNAME,  # should be ignored
+                    "password": TEST_PASSWORD,  # should be ignored
+                }
+            },
+            {
+                "name": "ssl-no_file",
+                "user": {
+                    "token": TEST_DATA_BASE64,
+                    "client-certificate": TEST_CLIENT_CERT,
+                    "client-key": TEST_CLIENT_KEY,
+                }
+            },
+            {
+                "name": "ssl",
+                "user": {
+                    "token": TEST_DATA_BASE64,
+                    "client-certificate-data": TEST_CLIENT_CERT_BASE64,
+                    "client-key-data": TEST_CLIENT_KEY_BASE64,
+                }
+            },
+        ]
+    }
+
+    def test_no_user_context(self):
+        expected = FakeConfig(host=TEST_HOST)
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="no_user",
+            client_configuration=actual).load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_simple_token(self):
+        expected = FakeConfig(host=TEST_HOST, token=TEST_DATA_BASE64)
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="simple_token",
+            client_configuration=actual).load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_load_user_token(self):
+        loader = KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="simple_token")
+        self.assertTrue(loader._load_user_token())
+        self.assertEqual(TEST_DATA_BASE64, loader.token)
+
+    def test_gcp(self):
+        expected = FakeConfig(host=TEST_HOST, token=TEST_ANOTHER_DATA_BASE64)
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="gcp",
+            client_configuration=actual,
+            get_google_credentials=lambda: TEST_ANOTHER_DATA_BASE64) \
+            .load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_load_gcp_token(self):
+        loader = KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="gcp",
+            get_google_credentials=lambda: TEST_ANOTHER_DATA_BASE64)
+        self.assertTrue(loader._load_gcp_token())
+        self.assertEqual(TEST_ANOTHER_DATA_BASE64, loader.token)
+
+    def test_user_pass(self):
+        expected = FakeConfig(host=TEST_HOST, token=TEST_BASIC_TOKEN)
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="user_pass",
+            client_configuration=actual).load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_load_user_pass_token(self):
+        loader = KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="user_pass")
+        self.assertTrue(loader._load_user_pass_token())
+        self.assertEqual(TEST_BASIC_TOKEN, loader.token)
+
+    def test_ssl_no_cert_files(self):
+        expected = FakeConfig(
+            host=TEST_SSL_HOST,
+            token=TEST_DATA_BASE64,
+            cert_file=TEST_CLIENT_CERT,
+            key_file=TEST_CLIENT_KEY,
+            ssl_ca_cert=TEST_CERTIFICATE_AUTH
+        )
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="ssl-no_file",
+            client_configuration=actual).load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_ssl(self):
+        expected = FakeConfig(
+            host=TEST_SSL_HOST,
+            token=TEST_DATA_BASE64,
+            cert_file=self._create_temp_file(TEST_CLIENT_CERT),
+            key_file=self._create_temp_file(TEST_CLIENT_KEY),
+            ssl_ca_cert=self._create_temp_file(TEST_CERTIFICATE_AUTH)
+        )
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="ssl",
+            client_configuration=actual).load_and_set()
+        self.assertEqual(expected, actual)
+
+    def test_list_contexts(self):
+        loader = KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="no_user")
+        actual_contexts = loader.list_contexts()
+        expected_contexts = ConfigNode("", self.TEST_KUBE_CONFIG)['contexts']
+        for actual in actual_contexts:
+            expected = expected_contexts.get_with_name(actual['name'])
+            self.assertEqual(expected.value, actual)
+
+    def test_current_context(self):
+        loader = KubeConfigLoader(config_dict=self.TEST_KUBE_CONFIG)
+        expected_contexts = ConfigNode("", self.TEST_KUBE_CONFIG)['contexts']
+        self.assertEqual(expected_contexts.get_with_name("no_user").value,
+                         loader.current_context)
+
+    def test_set_active_context(self):
+        loader = KubeConfigLoader(config_dict=self.TEST_KUBE_CONFIG)
+        loader.set_active_context("ssl")
+        expected_contexts = ConfigNode("", self.TEST_KUBE_CONFIG)['contexts']
+        self.assertEqual(expected_contexts.get_with_name("ssl").value,
+                         loader.current_context)
+
+
+if __name__ == '__main__':
+    unittest.main()