How to get kafka message's headers in Kafka Connect Sink connector with MongoDB

Question

How do I retrieve incoming headers from the kafka message with Kafka Connect to store them as additional data fields with MongoDB Sink Connector to mongodb.

I have a kafka topic "PROJECT_EXAMPLE_TOPIC". As you see I am already able to save msg timestamp, incoming message data and mongo document created/updated dates.

I guess there is a function to extract header somewhere.

Example kafka value

  // incoming kafka value
  {
    "msgId" : "exampleId"
  }

1. How to get original header header_foo ?

  //expected example
  {
  
    "_id" : ObjectId("5f83869c1ad2db246fa25a5a"),
    "_insertedTS" : ISODate("2020-10-11T22:26:36.051Z"),
    "_modifiedTS" : ISODate("2020-10-11T22:26:36.051Z"),
    "message_source" : "mongo_connector",
    "message_timestamp" : ISODate("2020-09-28T21:50:54.940Z"),
    "message_topic" : "PROJECT_EXAMPLE_TOPIC",
    "msgId" : "exampleId",
    "message_header_foo" : "header_foo_value"
   }

2. how to get all kafka headers ?

  //expected example
  {
    "_id" : ObjectId("5f83869c1ad2db246fa25a5a"),
    "_insertedTS" : ISODate("2020-10-11T22:26:36.051Z"),
    "_modifiedTS" : ISODate("2020-10-11T22:26:36.051Z"),
    "message_source" : "mongo_connector",
    "message_timestamp" : ISODate("2020-09-28T21:50:54.940Z"),
    "message_topic" : "PROJECT_EXAMPLE_TOPIC",
    "msgId" : "exampleId",
    "message_headers" : {
        "header_001" : "header_001_value",
        "header_002" : "header_002_value",
        ...
        "header_x" : "header_x_value"
    }
  }

There is my configuration

{
    "name": "sink-mongo-PROJECT-EXAMPLE",
    "config": {
      "topics": "PROJECT_EXAMPLE_TOPIC",
      "connector.class": "com.mongodb.kafka.connect.MongoSinkConnector",
      "tasks.max": "1",
  
      "key.converter": "org.apache.kafka.connect.storage.StringConverter",
      "key.converter.schema.registry.url": "SCHEMA_REGISTRY_URL",
      "key.converter.schemas.enable": "false",
      "key.converter.basic.auth.credentials.source": "USER_INFO",
      "key.converter.basic.auth.user.info": "SCHEMA_REGISTRY_API_KEY_AND_SECRET",
  
      "value.converter": "io.confluent.connect.avro.AvroConverter",
      "value.converter.schema.registry.url": "SCHEMA_REGISTRY_URL",
      "value.converter.schemas.enable": "false",
      "value.converter.basic.auth.credentials.source": "USER_INFO",
      "value.converter.basic.auth.user.info": "SCHEMA_REGISTRY_API_KEY_AND_SECRET",
      "connection.uri": "PROJECT_REFERENTIAL_MONGO_URL",
      "database": "PROJECT_DB_NAME",
      "collection": "EXAMPLE",
      "max.num.retries": "3",
      "retries.defer.timeout": "5000",
  
  
      "key.projection.type": "none",
      "key.projection.list": "",
  
      "field.renamer.mapping": "[]",
      "field.renamer.regex": "[]",
  
      "document.id.strategy": "com.mongodb.kafka.connect.sink.processor.id.strategy.BsonOidStrategy",
      "post.processor.chain": "com.mongodb.kafka.connect.sink.processor.DocumentIdAdder",
      "value.projection.list": "msgId",
      "value.projection.type": "whitelist",
      "writemodel.strategy": "com.mongodb.kafka.connect.sink.writemodel.strategy.UpdateOneTimestampsStrategy",
    
      "delete.on.null.values": "false",
    
      "max.batch.size": "0",
      "rate.limiting.timeout": "0",
      "rate.limiting.every.n": "0",
    
    
      "change.data.capture.handler": "",
  
      "errors.tolerance": "all",
      "errors.log.enable":true,
      "errors.log.include.messages":true,

      "transforms": "InsertSource,InsertTopic,InsertTimestamp",
      "transforms.InsertSource.type": "org.apache.kafka.connect.transforms.InsertField$Value",
      "transforms.InsertSource.static.field": "message_source",
      "transforms.InsertSource.static.value": "mongo_connector",
      "transforms.InsertTopic.type": "org.apache.kafka.connect.transforms.InsertField$Value",
      "transforms.InsertTopic.topic.field": "message_topic",
      "transforms.InsertTimestamp.type": "org.apache.kafka.connect.transforms.InsertField$Value",
      "transforms.InsertTimestamp.timestamp.field": "message_timestamp"

    }
  }

Answer 1

This is a bit of an old question, but there is a 3rd party message transform that can convert headers to fields on either key or value

https://jcustenborder.github.io/kafka-connect-documentation/projects/kafka-connect-transform-common/transformations/HeaderToField.html

This won't allow you to grab all headers though, you need to specify by name the ones you want to extract and their type.