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

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guoweiM commented on a change in pull request #13576:
URL: https://github.com/apache/flink/pull/13576#discussion_r502987944



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File path: flink-core/src/main/java/org/apache/flink/api/connector/sink/Writer.java
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@@ -0,0 +1,73 @@
+/*
+ * 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 java.util.List;
+
+/**
+ * The interface is responsible for writing data and handling any potential tmp area used to write yet un-staged data, e.g. in-progress files.
+ * The data (or metadata pointing to where the actual data is staged) ready to commit is returned to the system by the {@link #prepareCommit(boolean)}.
+ *
+ * @param <InputT>         The type of the writer's input
+ * @param <CommT>          The type of the committable data
+ * @param <WriterStateT>   The type of the writer's state
+ */
+@Experimental
+public interface Writer<InputT, CommT, WriterStateT> extends AutoCloseable {
+
+	/**
+	 * Add an element to the writer.
+	 * @param element The input record
+	 * @param context The additional information about the input record
+	 */
+	void write(InputT element, Context context);
+
+	/**
+	 * Prepare for a commit.
+	 * @param flush whether flushing the un-staged data or not
+	 * @return The data is ready to commit.
+	 */
+	List<CommT> prepareCommit(boolean flush);
+
+	/**
+	 * @return the writer's state.
+	 */
+	List<WriterStateT> snapshotState();

Review comment:
       Currently the benefit of `List<WriterStateT>` is that this could rebalance the workload when changing the parallelism. For example currently the `StreamingFileSink` redistributed the `Bucket` when the parallelism scales up or down.




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