[GitHub] [flink] fapaul commented on a change in pull request #17520: [FLINK-24565][avro] Port avro file format factory to BulkReaderFormatFactory

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fapaul commented on a change in pull request #17520:
URL: https://github.com/apache/flink/pull/17520#discussion_r738492071



##########
File path: flink-formats/flink-avro/src/main/java/org/apache/flink/formats/avro/AbstractAvroBulkFormat.java
##########
@@ -0,0 +1,207 @@
+/*
+ * 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.formats.avro;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.connector.file.src.FileSourceSplit;
+import org.apache.flink.connector.file.src.reader.BulkFormat;
+import org.apache.flink.connector.file.src.util.CheckpointedPosition;
+import org.apache.flink.connector.file.src.util.IteratorResultIterator;
+import org.apache.flink.connector.file.src.util.Pool;
+import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.formats.avro.utils.FSDataInputStreamWrapper;
+
+import org.apache.avro.Schema;
+import org.apache.avro.file.DataFileReader;
+import org.apache.avro.file.SeekableInput;
+import org.apache.avro.generic.GenericDatumReader;
+import org.apache.avro.io.DatumReader;
+
+import javax.annotation.Nullable;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+/** Provides a {@link BulkFormat} for Avro records. */
+@Internal
+public abstract class AbstractAvroBulkFormat<A, T, SplitT extends FileSourceSplit>
+        implements BulkFormat<T, SplitT> {
+
+    private static final long serialVersionUID = 1L;
+
+    protected final Schema readerSchema;
+
+    protected AbstractAvroBulkFormat(Schema readerSchema) {
+        this.readerSchema = readerSchema;
+    }
+
+    @Override
+    public AvroReader createReader(Configuration config, SplitT split) throws IOException {
+        open(split);
+        return createReader(split);
+    }
+
+    @Override
+    public AvroReader restoreReader(Configuration config, SplitT split) throws IOException {
+        open(split);
+        return createReader(split);
+    }
+
+    @Override
+    public boolean isSplittable() {
+        return true;
+    }
+
+    private AvroReader createReader(SplitT split) throws IOException {
+        long end = split.offset() + split.length();
+        if (split.getReaderPosition().isPresent()) {
+            CheckpointedPosition position = split.getReaderPosition().get();
+            return new AvroReader(
+                    split.path(),
+                    split.offset(),
+                    end,
+                    position.getOffset(),
+                    position.getRecordsAfterOffset());
+        } else {
+            return new AvroReader(split.path(), split.offset(), end, -1, 0);
+        }
+    }
+
+    protected void open(SplitT split) {}
+
+    protected abstract T convert(A record);
+
+    protected abstract A createReusedAvroRecord();
+
+    private class AvroReader implements BulkFormat.Reader<T> {
+
+        private final DataFileReader<A> reader;
+
+        private final long end;
+        private final Pool<A> pool;
+
+        private long currentBlockStart;
+        private long currentRecordsToSkip;
+
+        private AvroReader(Path path, long offset, long end, long blockStart, long recordsToSkip)
+                throws IOException {
+            A reuse = createReusedAvroRecord();
+
+            this.reader = createReaderFromPath(path);
+            if (blockStart >= 0) {
+                reader.seek(blockStart);
+            } else {
+                reader.sync(offset);
+            }
+            for (int i = 0; i < recordsToSkip; i++) {
+                reader.next(reuse);
+            }
+
+            this.end = end;
+            this.pool = new Pool<>(1);

Review comment:
       Can you explain a bit the pool size? If I understand it correctly the fetcher thread is blocked as long the record has not been consumed. In contrary to the `ParquetVectorizedInputFormat` we cannot configure it here to control the throughput.
   
   I am slightly worried that for small Avro objects the synchronization is more expensive than the actual safe in object allocations.
   
   Do I miss something? 




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