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Instrumentation of Java libraries using OpenTelemetry.

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/*
 * Copyright The OpenTelemetry Authors
 * SPDX-License-Identifier: Apache-2.0
 */

package io.opentelemetry.instrumentation.kafka.internal;

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.context.Context;
import org.apache.kafka.clients.ApiVersions;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.record.RecordBatch;

/**
 * This class is internal and is hence not for public use. Its APIs are unstable and can change at
 * any time.
 */
public final class KafkaPropagation {

  private static final KafkaHeadersSetter SETTER = KafkaHeadersSetter.INSTANCE;

  // Do not inject headers for batch versions below 2
  // This is how similar check is being done in Kafka client itself:
  // https://github.com/apache/kafka/blob/05fcfde8f69b0349216553f711fdfc3f0259c601/clients/src/main/java/org/apache/kafka/common/record/MemoryRecordsBuilder.java#L411-L412
  // Also, do not inject headers if specified by JVM option or environment variable
  // This can help in mixed client environments where clients < 0.11 that do not support
  // headers attempt to read messages that were produced by clients > 0.11 and the magic
  // value of the broker(s) is >= 2
  public static boolean shouldPropagate(ApiVersions apiVersions) {
    return apiVersions.maxUsableProduceMagic() >= RecordBatch.MAGIC_VALUE_V2;
  }

  public static  ProducerRecord propagateContext(
      Context context, ProducerRecord record) {
    try {
      inject(context, record);
    } catch (IllegalStateException e) {
      // headers must be read-only from reused record. try again with new one.
      record =
          new ProducerRecord<>(
              record.topic(),
              record.partition(),
              record.timestamp(),
              record.key(),
              record.value(),
              record.headers());

      inject(context, record);
    }
    return record;
  }

  private static  void inject(Context context, ProducerRecord record) {
    GlobalOpenTelemetry.getPropagators()
        .getTextMapPropagator()
        .inject(context, record.headers(), SETTER);
  }

  private KafkaPropagation() {}
}