Added support for Pure Python Functions (apache#193)

pulsar-functions/python-examples/pure_python_function_exclamation.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+#
+
+def process(self, input, context):
+  return input + '!'

pulsar-functions/runtime/src/main/python/python_instance.py

@@ -140,7 +140,10 @@ def run(self):
       )
 
     function_kclass = util.import_class(os.path.dirname(self.user_code), self.instance_config.function_config.className, try_internal=True)
-    self.function_class = function_kclass()
+    try:
+      self.function_class = function_kclass()
+    except:
+      self.function_class = function_kclass
 
     self.contextimpl = contextimpl.ContextImpl(self.instance_config, Log, self.pulsar_client, self.user_code, self.consumers)
     # Now launch a thread that does execution