Adding Py3.5.2+ support (#70)

In order to make FDL work with Python 3.5.2+ the following changes
 needed:

 - "start_serving" available from 3.7.1, so, i had to do some plumbing and version checks
 - importlib available also from 3.7.1, but it was available before but with different API,
   as for now it is considered as deprecated in favour of "importlib"

Closes: #69

Author: denismakogon

fdk/async_http/server.py

@@ -25,6 +25,8 @@
 
 from .protocol import HttpProtocol
 
+from fdk import constants
+
 
 class Signal(object):
     stopped = False
@@ -149,13 +151,20 @@ def serve(
         debug=debug,
     )
 
-    server_coroutine = loop.create_server(
-        server,
+    create_server_kwargs = dict(
         ssl=ssl,
         reuse_port=reuse_port,
         sock=sock,
         backlog=backlog,
-        start_serving=False
+    )
+
+    if constants.is_py37():
+        create_server_kwargs.update(
+            start_serving=False
+        )
+
+    server_coroutine = loop.create_server(
+        server, **create_server_kwargs
     )
 
     # Instead of pulling time at the end of every request,
@@ -188,14 +197,17 @@ def serve(
                 )
 
     def start_serving():
-        loop.run_until_complete(http_server.start_serving())
+        if constants.is_py37():
+            loop.run_until_complete(http_server.start_serving())
 
     def start():
         pid = os.getpid()
         try:
             logger.info("Starting worker [%s]", pid)
-            loop.run_until_complete(http_server.serve_forever())
-            # loop.run_forever()
+            if constants.is_py37():
+                loop.run_until_complete(http_server.serve_forever())
+            else:
+                loop.run_forever()
         finally:
             http_server.close()
             loop.run_until_complete(http_server.wait_closed())

fdk/constants.py

@@ -12,6 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import sys
+
 ASYNC_IO_READ_BUFFER = 65536
 DEFAULT_DEADLINE = 30
 HTTPSTREAM = "http-stream"
@@ -29,3 +31,9 @@
 CONTENT_LENGTH = "Content-Length"
 FN_ENFORCED_RESPONSE_CODES = [200, 502, 504]
 FN_DEFAULT_RESPONSE_CODE = 200
+
+
+# todo: python 3.8 is on its way, make more flexible
+def is_py37():
+    py_version = sys.version_info
+    return (py_version.major, py_version.minor) == (3, 7)

fdk/customer_code.py

@@ -12,26 +12,81 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
 
-class Function(object):
+from fdk import constants
 
-    def __init__(self, func_module_path, entrypoint="handler"):
-        self.spec, self.mod = self.import_from_source(func_module_path)
+
+def get_delayed_module_init_class():
+    if constants.is_py37():
+        return Python37DelayedImport
+    else:
+        return Python35plusDelayedImport
+
+
+class PythonDelayedImportAbstraction(object):
+
+    def __init__(self, func_module_path):
+        self._mod_path = func_module_path
         self._executed = False
-        self._entrypoint = entrypoint
 
-    @staticmethod
-    def import_from_source(func_module_path):
+    @property
+    def executed(self):
+        return self._executed
+
+    @executed.setter
+    def executed(self, exec_flag):
+        self._executed = exec_flag
+
+    def get_module(self):
+        raise Exception("Not implemented")
+
+
+class Python35plusDelayedImport(PythonDelayedImportAbstraction):
+
+    def __init__(self, func_module_path):
+        self._func_module = None
+        super(Python35plusDelayedImport, self).__init__(func_module_path)
+
+    def get_module(self):
+        if not self.executed:
+            import imp
+            fname, ext = os.path.splitext(
+                os.path.basename(self._mod_path))
+            self._func_module = imp.load_source(fname, self._mod_path)
+            self.executed = True
+
+        return self._func_module
+
+
+class Python37DelayedImport(PythonDelayedImportAbstraction):
+
+    def import_from_source(self):
         from importlib import util
         func_module_spec = util.spec_from_file_location(
-            "func", func_module_path
+            "func", self._mod_path
         )
         func_module = util.module_from_spec(func_module_spec)
-        return func_module_spec, func_module
+        self._func_module_spec = func_module_spec
+        self._func_module = func_module
+
+    def get_module(self):
+        if not self.executed:
+            self.import_from_source()
+            self._func_module_spec.loader.exec_module(
+                self._func_module)
+            self.executed = True
+
+        return self._func_module
 
-    def handler(self):
-        if self._executed is False:
-            self.spec.loader.exec_module(self.mod)
-            self._executed = True
 
-        return getattr(self.mod, self._entrypoint)
+class Function(object):
+
+    def __init__(self, func_module_path, entrypoint="handler"):
+        dm = get_delayed_module_init_class()
+        self._delayed_module_class = dm(func_module_path)
+        self._entrypoint = entrypoint
+
+    def handler(self):
+        mod = self._delayed_module_class.get_module()
+        return getattr(mod, self._entrypoint)

fdk/tests/test_delayed_loader.py

@@ -0,0 +1,53 @@
+# All Rights Reserved.
+#
+#    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 pytest
+
+from fdk import constants
+from fdk import customer_code
+
+from fdk.tests import funcs
+
+
+@pytest.mark.skipif(constants.is_py37(),
+                    reason="this test is for Python 3.5.2+ only")
+def test_py352plus():
+    dm = customer_code.Python35plusDelayedImport(funcs.__file__)
+    assert dm.executed is False
+
+    m = dm.get_module()
+    assert dm.executed is True
+    assert m is not None
+
+
+@pytest.mark.skipif(not constants.is_py37(),
+                    reason="this test is for Python 3.7.1+ only")
+def test_py37():
+    dm = customer_code.Python37DelayedImport(funcs.__file__)
+    assert dm.executed is False
+
+    m = dm.get_module()
+    assert dm.executed is True
+    assert m is not None
+
+
+def test_generic_delayed_loader():
+    f = customer_code.Function(
+        funcs.__file__, entrypoint="content_type")
+    assert f is not None
+    assert f._delayed_module_class.executed is False
+
+    h = f.handler()
+    assert h is not None
+    assert f._delayed_module_class.executed is True

tox.ini

@@ -1,11 +1,12 @@
 [tox]
-envlist = py{3.7},pep8
+envlist = py{3.7,3.6},pep8
 skipsdist = True
 
 [testenv]
 basepython =
     pep8: python3.7
     py3.7: python3.7
+    py3.6: python3.6
 
 passenv =
         DOCKER_HOST
@@ -29,6 +30,9 @@ commands = {posargs}
 [testenv:py3.7]
 commands = pytest -v -s --tb=long --cov=fdk {toxinidir}/fdk/tests
 
+[testenv:py3.6]
+commands = pytest -v -s --tb=long --cov=fdk {toxinidir}/fdk/tests
+
 [flake8]
 ignore = H405,H404,H403,H401,H306,H304,H101,E303,H301,W503
 show-source = True