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Templates for consuming from and producing to Kafka topics with Swim

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// Copyright 2015-2024 Nstream, inc.
//
// Licensed under the Redis Source Available License 2.0 (RSALv2) Agreement;
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://redis.com/legal/rsalv2-agreement/
//
// 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 nstream.adapter.kafka;

import java.util.Properties;
import nstream.adapter.common.AdapterSettings;
import nstream.adapter.common.egress.PublisherAgent;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import swim.structure.Value;

public abstract class KafkaPublishingAgent
    extends PublisherAgent> {

  public KafkaPublishingAgent() {
  }

  protected Producer kafkaProducer;

  protected Producer kafkaProducer() {
    return this.kafkaProducer;
  }

  protected void assignProducer(Producer producer) {
    if (this.kafkaProducer != null) {
      throw new RuntimeException(nodeUri() + ": producer already assigned");
    }
    this.kafkaProducer = producer;
  }

  protected void assignProducer(Properties loadConf, Runnable onSuccess) {
    if (this.kafkaProducer != null) {
      throw new RuntimeException(nodeUri() + ": producer already assigned");
    }
    execute(() -> {
      try {
        this.kafkaProducer = new KafkaProducer<>(loadConf);
      } catch (Exception e) {
        throw new RuntimeException(nodeUri() + ": failed to assign producer", e);
      }
      onSuccess.run();
    });
  }

  @Override
  protected AdapterSettings parseEgressSettings(Value prop) {
    return null; // FIXME
  }

  @Override
  protected void publish(ProducerRecord publishable) {
    if (this.kafkaProducer == null) {
      throw new RuntimeException(nodeUri() + ": can't publish before assigning producer");
    }
    this.kafkaProducer.send(publishable, (m, e) -> {
      if (e != null) {
        didFail(new RuntimeException(nodeUri()
            + ": exception thrown while producing message with offset " + m.offset(), e));
      }
    });
  }

  @Override
  public void didStart() {
    info(nodeUri() + ": didStart");
    stagePublication();
  }

}