Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/3838#discussion_r133159049
--- Diff:
flink-libraries/flink-streaming-python/src/main/java/org/apache/flink/streaming/python/api/functions/PythonOutputSelector.java
---
@@ -0,0 +1,62 @@
+/*
+ * 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.
+ */
+package org.apache.flink.streaming.python.api.functions;
+
+import org.apache.flink.streaming.api.collector.selector.OutputSelector;
+import
org.apache.flink.streaming.python.util.serialization.SerializationUtils;
+import org.python.core.PyObject;
+
+import java.io.IOException;
+
+/**
+ * The {@code PythonOutputSelector} is a thin wrapper layer over a Python
UDF {@code OutputSelector}.
+ * It receives an {@code OutputSelector} as an input and keeps it
internally in a serialized form.
+ * It is then delivered, as part of the job graph, up to the TaskManager,
then it is opened and becomes
+ * a sort of mediator to the Python UDF {@code OutputSelector}.
+ *
+ * <p>This function is used internally by the Python thin wrapper layer
over the streaming data
+ * functionality</p>
+ */
+public class PythonOutputSelector implements OutputSelector<PyObject> {
+ private static final long serialVersionUID = 909266346633598177L;
+
+ private final byte[] serFun;
+ private transient OutputSelector<PyObject> fun;
+
+ public PythonOutputSelector(OutputSelector<PyObject> fun) throws
IOException {
+ this.serFun = SerializationUtils.serializeObject(fun);
+ }
+
+ @Override
+ @SuppressWarnings("unchecked")
+ public Iterable<String> select(PyObject value) {
+ if (this.fun == null) {
+ try {
+ this.fun = (OutputSelector<PyObject>)
SerializationUtils.deserializeObject(this.serFun);
+ } catch (IOException e) {
+ e.printStackTrace();
--- End diff --
I would throw a RuntimeException to fail the job. If the function can't be
deserialized something went terribly wrong during deployment.
Returning null would cause an NPE later on in `DirectedOutput`, obfuscating
what actually caused the error.
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