Add watch stream support

k8sutil/__init__.py

@@ -13,3 +13,4 @@
 # limitations under the License.
 
 from .kube_config import load_kube_config
+from .watch import Watch

k8sutil/watch.py

@@ -0,0 +1,123 @@
+# 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 json
+import pydoc
+
+import k8sclient
+
+PYDOC_RETURN_LABEL = ":return:"
+
+# Removing this suffix from return type name should give us event's object
+# type. e.g., if list_namespaces() returns "NamespaceList" type,
+# then list_namespaces(watch=true) returns a stream of events with objects
+# of type "Namespace". In case this assumption is not true, user should
+# provide return_type to Watch class's __init__.
+TYPE_LIST_SUFFIX = "List"
+
+
+class SimpleNamespace:
+
+    def __init__(self, **kwargs):
+        self.__dict__.update(kwargs)
+
+
+def _find_return_type(func):
+    for line in pydoc.getdoc(func).splitlines():
+        if line.startswith(PYDOC_RETURN_LABEL):
+            return line[len(PYDOC_RETURN_LABEL):].strip()
+    return ""
+
+
+def iter_resp_lines(resp):
+    prev = ""
+    for seg in resp.read_chunked(decode_content=False):
+        if isinstance(seg, bytes):
+            seg = seg.decode('utf8')
+        seg = prev + seg
+        lines = seg.split("\n")
+        if not seg.endswith("\n"):
+            prev = lines[-1]
+            lines = lines[:-1]
+        else:
+            prev = ""
+        for line in lines:
+            if line:
+                yield line
+
+
+class Watch(object):
+
+    def __init__(self, return_type=None):
+        self._raw_return_type = return_type
+        self._stop = False
+        self._api_client = k8sclient.ApiClient()
+
+    def stop(self):
+        self._stop = True
+
+    def get_return_type(self, func):
+        if self._raw_return_type:
+            return self._raw_return_type
+        return_type = _find_return_type(func)
+        if return_type.endswith(TYPE_LIST_SUFFIX):
+            return return_type[:-len(TYPE_LIST_SUFFIX)]
+        return return_type
+
+    def unmarshal_event(self, data, return_type):
+        js = json.loads(data)
+        js['raw_object'] = js['object']
+        if return_type:
+            obj = SimpleNamespace(data=json.dumps(js['raw_object']))
+            js['object'] = self._api_client.deserialize(obj, return_type)
+        return js
+
+    def stream(self, func, *args, **kwargs):
+        """Watch an API resource and stream the result back via a generator.
+
+        :param func: The API function pointer. Any parameter to the function
+                     can be passed after this parameter.
+
+        :return: Event object with these keys:
+                   'type': The type of event such as "ADDED", "DELETED", etc.
+                   'raw_object': a dict representing the watched object.
+                   'object': A model representation of raw_object. The name of
+                             model will be determined based on
+                             the func's doc string. If it cannot be determined,
+                             'object' value will be the same as 'raw_object'.
+
+        Example:
+            v1 = k8sclient.CoreV1Api()
+            watch = k8sutil.Watch()
+            for e in watch.stream(v1.list_namespace, resource_version=1127):
+                type = e['type']
+                object = e['object']  # object is one of type return_type
+                raw_object = e['raw_object']  # raw_object is a dict
+                ...
+                if should_stop:
+                    watch.stop()
+        """
+
+        return_type = self.get_return_type(func)
+        kwargs['watch'] = True
+        kwargs['_preload_content'] = False
+        resp = func(*args, **kwargs)
+        try:
+            for line in iter_resp_lines(resp):
+                yield self.unmarshal_event(line, return_type)
+                if self._stop:
+                    break
+        finally:
+            resp.close()
+            resp.release_conn()