[GitHub] [flink] stevenzwu commented on a change in pull request #13576: [FLINK-19512] Introduce the new sink API

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stevenzwu commented on a change in pull request #13576:
URL: https://github.com/apache/flink/pull/13576#discussion_r502731108



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File path: flink-core/src/main/java/org/apache/flink/api/connector/sink/Sink.java
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@@ -0,0 +1,94 @@
+/*
+ * 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.api.connector.sink;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.core.io.SimpleVersionedSerializer;
+import org.apache.flink.metrics.MetricGroup;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * This interface lets the sink developer build a simple sink topology, which could guarantee the exactly once
+ * semantics in both batch and stream execution mode if there is a {@link Committer} or {@link GlobalCommitter}.
+ * 1. The {@link Writer} is responsible for producing the committable.
+ * 2. The {@link Committer} is responsible for committing a single committable.
+ * 3. The {@link GlobalCommitter} is responsible for committing an aggregated committable, which we called the global
+ *    committable. There is only one instance of the {@link GlobalCommitter}.
+ * Note: Developers need to ensure the idempotence of {@link Committer} and {@link GlobalCommitter}.
+ *
+ * @param <InputT>        The type of the sink's input
+ * @param <CommT>         The type of the committable data
+ * @param <GlobalCommT>   The type of the aggregated committable
+ * @param <WriterStateT>  The type of the writer's state
+ */
+@Experimental
+public interface Sink<InputT, CommT, GlobalCommT, WriterStateT> {
+
+	/**
+	 * Create a {@link Writer}.
+	 * @param context the runtime context.
+	 * @param states the writer's state.
+	 * @return A sink writer.
+	 */
+	Writer<InputT, CommT, WriterStateT> createWriter(InitContext context, List<WriterStateT> states);

Review comment:
       curious about the `List<WriterStateT> states`. is it similar to union state? each writer subtask should choose the `WriteStateT` applicable to itself?




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