[GitHub] [hudi] YuweiXiao commented on a diff in pull request #6737: [HUDI-4373] Flink Consistent hashing bucket index write path code

[GitBox <gi...@apache.org>]

YuweiXiao commented on code in PR #6737:
URL: https://github.com/apache/hudi/pull/6737#discussion_r990745955


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hudi-flink-datasource/hudi-flink/src/main/java/org/apache/hudi/sink/bucket/ConsistentBucketStreamWriteFunction.java:
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@@ -0,0 +1,120 @@
+/*
+ * 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.hudi.sink.bucket;
+
+import org.apache.hudi.common.fs.FSUtils;
+import org.apache.hudi.common.model.ConsistentHashingNode;
+import org.apache.hudi.common.model.HoodieConsistentHashingMetadata;
+import org.apache.hudi.common.model.HoodieKey;
+import org.apache.hudi.common.model.HoodieRecord;
+import org.apache.hudi.common.model.HoodieRecordLocation;
+import org.apache.hudi.common.util.Option;
+import org.apache.hudi.common.util.StringUtils;
+import org.apache.hudi.common.util.ValidationUtils;
+import org.apache.hudi.configuration.FlinkOptions;
+import org.apache.hudi.index.bucket.ConsistentBucketIdentifier;
+import org.apache.hudi.index.bucket.ConsistentBucketIndexUtils;
+import org.apache.hudi.sink.StreamWriteFunction;
+
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.runtime.state.FunctionInitializationContext;
+import org.apache.flink.streaming.api.functions.ProcessFunction;
+import org.apache.flink.util.Collector;
+import org.apache.flink.util.Preconditions;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A stream write function with consistent hashing bucket index.
+ *
+ * @param <I> the input type
+ */
+public class ConsistentBucketStreamWriteFunction<I> extends StreamWriteFunction<I> {
+
+  private static final Logger LOG = LoggerFactory.getLogger(ConsistentBucketStreamWriteFunction.class);
+
+  private List<String> indexKeyFields;
+  private Map<String, ConsistentBucketIdentifier> partitionToIdentifier;
+  /**
+   * Cache mapping between node -> location, to avoid repeated creation of the same location objects.
+   */
+  private Map<ConsistentHashingNode, HoodieRecordLocation> nodeToRecordLocation;
+
+  /**
+   * Constructs a StreamingSinkFunction.
+   *
+   * @param config The config options
+   */
+  public ConsistentBucketStreamWriteFunction(Configuration config) {
+    super(config);
+  }
+
+  @Override
+  public void open(Configuration parameters) throws IOException {
+    super.open(parameters);
+    this.indexKeyFields = Arrays.asList(config.getString(FlinkOptions.INDEX_KEY_FIELD).split(","));
+
+    this.partitionToIdentifier = new HashMap<>();
+    this.nodeToRecordLocation = new HashMap<>();
+  }
+
+  @Override
+  public void initializeState(FunctionInitializationContext context) throws Exception {
+    super.initializeState(context);
+  }
+
+  @Override
+  public void snapshotState() {
+    super.snapshotState();
+  }
+
+  @Override
+  public void processElement(I value, ProcessFunction<I, Object>.Context ctx, Collector<Object> out) throws Exception {
+    HoodieRecord<?> record = (HoodieRecord<?>) value;
+    final HoodieKey hoodieKey = record.getKey();
+    final String partition = hoodieKey.getPartitionPath();
+
+    ConsistentHashingNode node = getBucketIdentifier(partition).getBucket(hoodieKey, indexKeyFields);
+    Preconditions.checkArgument(!StringUtils.isNullOrEmpty(node.getFileIdPrefix()),
+        "Consistent hashing node has no file group, partition: " + partition + ", meta: "
+            + partitionToIdentifier.get(partition).getMetadata().getFilename() + ", record_key: " + hoodieKey);
+
+    record.unseal();
+    record.setCurrentLocation(nodeToRecordLocation.computeIfAbsent(node,
+        n -> new HoodieRecordLocation("U", FSUtils.createNewFileId(n.getFileIdPrefix(), 0))));

Review Comment:
   I took another look at the code. Differently from SIMPLE bucket index, setting `I` for first write in the context of consistent hashing would require checking the existence of file slices, which introduces a huge overhead. And we may need to handle race conditions when we have concurrent clustering.
   
   Setting it to `U` will produce log-file-only file group for the first write and will not break any constraints regarding convention or correctness. And the benefit is a performance gain since we no longer need to obtain a FileSystemView and do the check. I will stick to `U` for now. What is your opinion?



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