Github user pnowojski commented on a diff in the pull request:
https://github.com/apache/flink/pull/4955#discussion_r149322930
--- Diff:
flink-connectors/flink-connector-kafka-0.11/src/main/java/org/apache/flink/streaming/connectors/kafka/internal/TransactionalIdsGenerator.java
---
@@ -0,0 +1,86 @@
+/*
+ * 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.connectors.kafka.internal;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * Class responsible for generating transactional ids to use when
communicating with Kafka.
+ *
+ * <p>It guarantees that:
+ * - generated ids to use will never clash with ids to use from different
subtasks
+ * - generated ids to abort will never clash with ids to abort from
different subtasks
+ * - generated ids to use will never clash with ids to abort from
different subtasks
+ *
+ * <p>In other words, any particular generated id will always be assigned
to one and only one subtask.
+ */
+public class TransactionalIdsGenerator {
--- End diff --
ops, forgot about it
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