Create a Debezium source connector from MongoDB to Apache Kafka®
================================================================

The Debezium source connector for MongoDB tracks database changes using a MongoDB replica set or shared cluster, and writes them to an Apache Kafka® topic in a standard format where they can be transformed and read by multiple consumers.

.. note::

    You can check the full set of available parameters and configuration options in the `connector's documentation <https://debezium.io/docs/connectors/mongodb/>`_.

.. _connect_debezium_mongodb_source_prereq:

Prerequisites
-------------

To setup a Debezium source connector pointing to MongoDB, you need an Aiven for Apache Kafka service :doc:`with Kafka Connect enabled <enable-connect>` or a :ref:`dedicated Aiven for Apache Kafka Connect cluster <apache_kafka_connect_dedicated_cluster>`. 

Furthermore you need to collect the following information about the source MongoDB database upfront:

* ``MONGODB_HOST``: The database hostname
* ``MONGODB_PORT``: The database port
* ``MONGODB_USER``: The database user to connect
* ``MONGODB_PASSWORD``: The database password for the ``MONGODB_USER``
* ``MONGODB_DATABASE_NAME``: The database name to include in the replica
* ``MONGODB_REPLICA_SET_NAME``: The name of MongoDB's replica set
* ``APACHE_KAFKA_HOST``: The hostname of the Apache Kafka service, only needed when using Avro as data format
* ``SCHEMA_REGISTRY_PORT``: The Apache Kafka's schema registry port, only needed when using Avro as data format
* ``SCHEMA_REGISTRY_USER``: The Apache Kafka's schema registry username, only needed when using Avro as data format
* ``SCHEMA_REGISTRY_PASSWORD``: The Apache Kafka's schema registry user password, only needed when using Avro as data format


.. Note::

    If you're using Aiven for Apache Kafka®,  the Kafka related details are available in the `Aiven console <https://console.aiven.io/>`_ service Overview tab or via the dedicated ``avn service get`` command with the :ref:`Aiven CLI <avn_service_get>`.

Setup a MongoDB Debezium source connector with Aiven Console
------------------------------------------------------------

The following example demonstrates how to setup a Debezium source connector for Apache Kafka to a MongoDB database using the `Aiven Console <https://console.aiven.io/>`_.

Define a Kafka Connect configuration file
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Define the connector configurations in a file (we'll refer to it with the name ``debezium_source_mongodb.json``) with the following content. Creating a file is not strictly necessary but allows to have all the information in one place before copy/pasting them in the `Aiven Console <https://console.aiven.io/>`_:

.. code-block:: json

    {
        "name":"CONNECTOR_NAME",
        "connector.class": "io.debezium.connector.mongodb.MongoDbConnector",
        "mongodb.hosts": "MONGODB_REPLICA_SET_NAME/MONGODB_HOST:MONGODB_PORT",
        "mongodb.name" : "MONGODB_DATABASE_NAME",
        "mongodb.user": "MONGODB_USER",
        "mongodb.password": "MONGODB_PASSWORD",
        "tasks.max":"NR_TASKS",
        "key.converter": "io.confluent.connect.avro.AvroConverter",
        "key.converter.schema.registry.url": "https://APACHE_KAFKA_HOST:SCHEMA_REGISTRY_PORT",
        "key.converter.basic.auth.credentials.source": "USER_INFO",
        "key.converter.schema.registry.basic.auth.user.info": "SCHEMA_REGISTRY_USER:SCHEMA_REGISTRY_PASSWORD",
        "value.converter": "io.confluent.connect.avro.AvroConverter",
        "value.converter.schema.registry.url": "https://APACHE_KAFKA_HOST:SCHEMA_REGISTRY_PORT",
        "value.converter.basic.auth.credentials.source": "USER_INFO",
        "value.converter.schema.registry.basic.auth.user.info": "SCHEMA_REGISTRY_USER:SCHEMA_REGISTRY_PASSWORD"
    }

The configuration file contains the following entries:

* ``name``: the connector name, replace CONNECTOR_NAME with the name you want to use for the connector
* ``MONGODB_HOST``, ``MONGODB_PORT``, ``MONGODB_DATABASE_NAME``, ``MONGODB_USER``, ``MONGODB_PASSWORD`` and ``MONGODB_REPLICA_SET_NAME``: source database parameters collected in the :ref:`prerequisite <connect_debezium_mongodb_source_prereq>` phase. 
* ``tasks.max``: maximum number of tasks to execute in parallel. By default this is 1, the connector can use at most 1 task for each collection defined. Replace ``NR_TASKS`` with the amount of parallel task based on the number of input collections.
* ``key.converter`` and ``value.converter``:  defines the messages data format in the Apache Kafka topic. The ``io.confluent.connect.avro.AvroConverter`` converter pushes messages in Avro format. To store the messages schema we use Aiven's `Karapace schema registry <https://github.com/aiven/karapace>`_ as specified by the ``schema.registry.url`` parameter and related credentials.

  .. Note::

     The ``key.converter`` and ``value.converter`` sections are only needed when pushing data in Avro format. If omitted the messages will be defined in JSON format.

     The ``USER_INFO`` is **not** a placeholder, no substitution is needed for that parameter.


Create a Kafka Connect connector with the Aiven Console
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To create a Kafka Connect connector, follow these steps: 

1. Log in to the `Aiven Console <https://console.aiven.io/>`_ and select the Aiven for Apache Kafka® or Aiven for Apache Kafka Connect® service where the connector needs to be defined. 
2. Select **Connectors** from the left sidebar. 
3. Select **Create New Connector**, the button is enabled only for services :doc:`with Kafka Connect enabled <enable-connect>`.
4. Select **Debezium - MongoDB**.
5. In the **Common** tab, locate the **Connector configuration** text box and select on **Edit**.
6. Paste the connector configuration (stored in the ``debezium_source_mongodb.json`` file) in the form.
7. Select **Apply**.

   .. note::

      The Aiven Console parses the configuration file and fills the relevant UI fields. You can review the UI fields across the various tabs and change them if necessary. The changes will be reflected in JSON format in the **Connector configuration** text box.

8. After all the settings are correctly configured, select **Create new connector**.

   .. Tip::

      If you're using Aiven for Apache Kafka, topics will not be created automatically. Either create them manually following the ``database.server.name.schema_name.table_name`` naming pattern or enable the ``kafka.auto_create_topics_enable`` advanced parameter.
    
8. Verify the connector status under the **Connectors** screen. 
9. Verify the presence of the data in the target Apache Kafka topic coming from the MongoDB dataset. The topic name is equal to the concatenation of the database and collection name. If you need to change the target table name, you can do so using the Kafka Connect ``RegexRouter`` transformation.



You can also create connectors using the :ref:`Aiven CLI command <avn_service_connector_create>`.