content: /*
   * 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.kafka.streams.kstream.internals;
  
  import org.apache.kafka.common.metrics.Sensor;
  import org.apache.kafka.streams.processor.api.ProcessorContext;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.processor.api.RecordMetadata;
  
  import org.slf4j.Logger;
  
  public final class StreamStreamJoinUtil {
  
      private StreamStreamJoinUtil() {
      }
  
      public static <KIn, VIn, KOut, VOut> boolean skipRecord(
          final Record<KIn, VIn> record, final Logger logger,
          final Sensor droppedRecordsSensor,
          final ProcessorContext<KOut, VOut> context) {
          // we do join iff keys are equal, thus, if key is null we cannot join and just ignore the record
          //
          // we also ignore the record if value is null, because in a key-value data model a null-value indicates
          // an empty message (ie, there is nothing to be joined) -- this contrast SQL NULL semantics
          // furthermore, on left/outer joins 'null' in ValueJoiner#apply() indicates a missing record --
          // thus, to be consistent and to avoid ambiguous null semantics, null values are ignored
          if (record.key() == null || record.value() == null) {
              if (context.recordMetadata().isPresent()) {
                  final RecordMetadata recordMetadata = context.recordMetadata().get();
                  logger.warn(
                      "Skipping record due to null key or value. "
                          + "topic=[{}] partition=[{}] offset=[{}]",
                      recordMetadata.topic(), recordMetadata.partition(), recordMetadata.offset()
                  );
              } else {
                  logger.warn(
                      "Skipping record due to null key or value. Topic, partition, and offset not known."
                  );
              }
              droppedRecordsSensor.record();
              return true;
          } else {
              return false;
          }
      }
  }
  