Create a source connector from Couchbase to Apache Kafka®
=========================================================

The `Couchbase <https://www.couchbase.com/>`_ source connector pushes data from the NoSQL database, to Apache Kafka® where it can be transformed and read by multiple consumers.

.. Tip::

    Sourcing data from a database into Apache Kafka decouples the database from the set of consumers. Once the data is in Apache Kafka, multiple applications can access it without adding any additional query overhead to the source database.

.. note::

    You can check the full set of available parameters and configuration options in the `connector's documentation <https://github.com/couchbase/kafka-connect-couchbase>`_.

.. _connect_couchbase_source_prereq:

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

To setup a `Couchbase <https://www.couchbase.com/>`_ source connector, 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 Couchbase database upfront:

* ``COUCHBASE_SEED_NODES``: The database seed nodes
* ``COUCHBASE_USER``: The database user to connect
* ``COUCHBASE_PASSWORD``: The database password for the ``COUCHBASE_USER``
* ``COUCHBASE_BUCKET``: The bucket from which extract the data
* ``COUCHBASE_SCOPE``: The scope from which extract the data (if none all the scopes within the bucket will be sourced)
* ``COUCHBASE_COLLECTIONS``: The list of collections from which extract the data (if none all the collections within the bucket and scope will be sourced)
* ``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 Couchbase source connector with Aiven Console
------------------------------------------------------------

The following example demonstrates how to setup a Couchbase source connector for Apache Kafka 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 ``couchbase-source.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": "com.couchbase.connect.kafka.CouchbaseSourceConnector",
        "couchbase.seed.nodes": "COUCHBASE_SEED_NODES", 
        "couchbase.username": "COUCHBASE_USER",
        "couchbase.password": "COUCHBASE_PASSWORD",
        "couchbase.bucket": "COUCHBASE_BUCKET",
        "couchbase.scope": "COUCHBASE_SCOPE",
        "couchbase.collections": "COUCHBASE_COLLECTIONS",
        "couchbase.source.handler": "com.couchbase.connect.kafka.handler.source.RawJsonSourceHandler",
        "value.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",
    }

The configuration file contains the following entries:

* ``name``: the connector name, replace CONNECTOR_NAME with the name you want to use for the connector
* ``COUCHBASE_SEED_NODES``, ``COUCHBASE_BUCKET``, ``COUCHBASE_SCOPE``, ``COUCHBASE_COLLECTIONS``, ``COUCHBASE_USER``, ``COUCHBASE_PASSWORD``: source database parameters collected in the :ref:`prerequisite <connect_couchbase_source_prereq>` phase. 
* ``couchbase.source.handler`` and ``value.converter``:  defines the messages data format in the Apache Kafka topic. The combination of ``com.couchbase.connect.kafka.handler.source.RawJsonSourceHandler`` and ``org.apache.kafka.connect.converters.ByteArrayConverter`` pushes the Couchbase documents in the Kafka topic in JSON format. 


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 **Couchbase Source**.
5. In the **Common** tab, locate the **Connector configuration** text box and select on **Edit**.
6. Paste the connector configuration (stored in the ``couchbase-source.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 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.
    
9. Verify the connector status under the **Connectors** tab
10. 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.

.. note::

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


Example: define a Couchbase source connector
--------------------------------------------

The example creates an Couchbase source connector with the following properties:

* connector name: ``couchbase_source``
* Couchbase seeds: ``test.cloud.couchbase.com``
* Couchbase username: ``testuser``
* Couchbase password: ``Test123!`` 
* Couchbase bucket: ``travel-sample``
* Couchbase scope: ``inventory``
* Couchbase collections: ``airline``

The connector configuration is the following:

.. code::

    {
        "name": "couchbase_source",
        "connector.class": "com.couchbase.connect.kafka.CouchbaseSourceConnector",
        "couchbase.seed.nodes": "test.cloud.couchbase.com",
        "couchbase.username": "testuser",
        "couchbase.password": "Test123!",
        "couchbase.bucket": "travel-sample",
        "couchbase.scope": "inventory",
        "couchbase.collections": "airline",
        "couchbase.source.handler": "com.couchbase.connect.kafka.handler.source.RawJsonSourceHandler",
        "value.converter": "org.apache.kafka.connect.converters.ByteArrayConverter"
    }

With the above configuration stored in a ``couchbase-source.json`` file, you can create the connector in the ``demo-kafka`` instance and you should see the data landing in an Apache Kafka topic named ``${bucket}.${scope}.${collection}`` by default, you can change the landing topic logic by modifying the ``couchbase.topic`` parameter definition.

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