sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/kafka/KafkaTableProvider.java

/*
 * 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.beam.sdk.extensions.sql.meta.provider.kafka;

import static org.apache.beam.sdk.extensions.sql.meta.provider.kafka.Schemas.PAYLOAD_FIELD;
import static org.apache.beam.sdk.util.Preconditions.checkArgumentNotNull;

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.google.auto.service.AutoService;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTable;
import org.apache.beam.sdk.extensions.sql.meta.Table;
import org.apache.beam.sdk.extensions.sql.meta.provider.InMemoryMetaTableProvider;
import org.apache.beam.sdk.extensions.sql.meta.provider.TableProvider;
import org.apache.beam.sdk.schemas.Schema;
import org.apache.beam.sdk.schemas.io.payloads.PayloadSerializer;
import org.apache.beam.sdk.schemas.io.payloads.PayloadSerializers;

/**
 * Kafka table provider.
 *
 * <p>A sample of text table is:
 *
 * <pre>{@code
 * CREATE TABLE ORDERS(
 *   ID INT COMMENT 'this is the primary key',
 *   NAME VARCHAR(127) COMMENT 'this is the name'
 * )
 * COMMENT 'this is the table orders'
 * LOCATION 'kafka://localhost:2181/brokers?topic=test'
 * TBLPROPERTIES '{"bootstrap.servers":"localhost:9092", "topics": ["topic1", "topic2"]}'
 * }</pre>
 */
@AutoService(TableProvider.class)
public class KafkaTableProvider extends InMemoryMetaTableProvider {
  @Override
  public BeamSqlTable buildBeamSqlTable(Table table) {
    Schema schema = table.getSchema();

    JSONObject properties = table.getProperties();
    String bootstrapServers = properties.getString("bootstrap.servers");
    JSONArray topicsArr = properties.getJSONArray("topics");
    List<String> topics = new ArrayList<>(topicsArr.size());
    for (Object topic : topicsArr) {
      topics.add(topic.toString());
    }

    Optional<String> payloadFormat =
        properties.containsKey("format")
            ? Optional.of(properties.getString("format"))
            : Optional.empty();
    if (Schemas.isNestedSchema(schema)) {
      Optional<PayloadSerializer> serializer =
          payloadFormat.map(
              format ->
                  PayloadSerializers.getSerializer(
                      format,
                      checkArgumentNotNull(schema.getField(PAYLOAD_FIELD).getType().getRowSchema()),
                      properties.getInnerMap()));
      return new NestedPayloadKafkaTable(schema, bootstrapServers, topics, serializer);
    } else {
      /*
       * CSV is handled separately because multiple rows can be produced from a single message, which
       * adds complexity to payload extraction. It remains here and as the default because it is the
       * historical default, but it will not be extended to support attaching extended attributes to
       * rows.
       */
      if (payloadFormat.orElse("csv").equals("csv")) {
        return new BeamKafkaCSVTable(schema, bootstrapServers, topics);
      }
      PayloadSerializer serializer =
          PayloadSerializers.getSerializer(payloadFormat.get(), schema, properties.getInnerMap());
      return new PayloadSerializerKafkaTable(schema, bootstrapServers, topics, serializer);
    }
  }

  @Override
  public String getTableType() {
    return "kafka";
  }
}