Create a sink connector from Apache Kafka® to OpenSearch®

The OpenSearch sink connector enables you to move data from an Aiven for Apache Kafka® cluster to an OpenSearch® instance for further processing and analysis.

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This article describes how to create a sink connector to OpenSearch®. Similar instructions are available also for Elasticsearch® in the dedicated article.

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See the full set of available parameters and configuration options in the connector's documentation.

Prerequisites

To setup an OpenSearch sink connector, you need an Aiven for Apache Kafka service with Kafka Connect enabled or a dedicated Aiven for Apache Kafka Connect cluster.

Also collect the following information about the target OpenSearch service upfront:

OS_CONNECTION_URL: The OpenSearch connection URL, in the form of https://HOST:PORT
OS_USERNAME: The OpenSearch username to connect
OS_PASSWORD: The password for the username selected
TOPIC_LIST: The list of topics to sink divided by comma
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

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If you're using Aiven for OpenSearch® and Aiven for Apache Kafka® the above details are available in the Aiven console service Overview tab or via the dedicated avn service get command with the Aiven CLI.

The SCHEMA_REGISTRY related parameters are available in the Aiven for Apache Kafka® service page, Overview tab, and Schema Registry subtab

As of version 3.0, Aiven for Apache Kafka no longer supports Confluent Schema Registry. For more information, read the article describing the replacement, Karapace

Setup an OpenSearch sink connector with Aiven Console

The following example demonstrates how to setup a OpenSearch sink connector for Apache Kafka using the Aiven Console.

Define a Kafka Connect configuration file

Define the connector configurations in a file (we'll refer to it with the name opensearch_sink.json) with the following content:

{
    "name":"CONNECTOR_NAME",
    "connector.class": "io.aiven.kafka.connect.opensearch.OpensearchSinkConnector",
    "topics": "TOPIC_LIST",
    "connection.url": "OS_CONNECTION_URL",
    "connection.username": "OS_USERNAME",
    "connection.password": "OS_PASSWORD",
    "type.name": "TYPE_NAME",
    "tasks.max":"1",
    "key.ignore": "true",
    "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
connection.url, connection.username, connection.password: sink OpenSearch parameters collected in the prerequisite phase.
type.name: the OpenSearch type name to be used when indexing.
key.ignore: boolean flag dictating if to ignore the message key. If set to true, the document ID is generated as message's topic+partition+offset, the message key is used as ID otherwise.
tasks.max: maximum number of tasks to execute in parallel. By default this is 1.
key.converter and value.converter: defines the messages data format in the Apache Kafka topic. The io.confluent.connect.avro.AvroConverter converter translates messages from the Avro format. To retrieve the messages schema we use Aiven's Karapace schema registry as specified by the schema.registry.url parameter and related credentials.

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The key.converter and value.converter sections are only needed when the source data is in Avro format. If omitted the messages will be read as binary format.

When using Avro as source data format, set following parameters:

value.converter.schema.registry.url: pointing to the Aiven for Apache Kafka schema registry URL in the form of https://APACHE_KAFKA_HOST:SCHEMA_REGISTRY_PORT with the APACHE_KAFKA_HOST and SCHEMA_REGISTRY_PORT parameters retrieved in the previous step.
value.converter.basic.auth.credentials.source: to the value USER_INFO, since you're going to login to the schema registry using username and password.
value.converter.schema.registry.basic.auth.user.info: passing the required schema registry credentials in the form of SCHEMA_REGISTRY_USER:SCHEMA_REGISTRY_PASSWORD with the SCHEMA_REGISTRY_USER and SCHEMA_REGISTRY_PASSWORD parameters retrieved in the previous step.

Create a Kafka Connect connector with the Aiven Console

To create a Kafka Connect connector:

Log in to the Aiven Console and select the Aiven for Apache Kafka® or Aiven for Apache Kafka Connect® service where the connector needs to be defined.
Select Connectors from the left sidebar.
Select Create New Connector, it is enabled only for services with Kafka Connect enabled.
Select OpenSearch sink.
In the Common tab, locate the Connector configuration text box and select on Edit.
Paste the connector configuration (stored in the opensearch_sink.json file) in the form.
Select Apply.

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The Aiven Console parses the configuration file and fills the relevant UI fields. You can review the UI fields across the various tab and change them if necessary. The changes will be reflected in JSON format in the Connector configuration text box.
After all the settings are correctly configured, select Create connector.
Verify the connector status under the Connectors screen.
Verify the presence of the data in the target OpenSearch service, the index name is equal to the Apache Kafka topic name.

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You can also create connectors using the Aiven CLI command.

Create daily OpenSearch indices

You might need to create an OpenSearch index on daily basis to store the Apache Kafka messages. Adding the following TimestampRouter transformation in the connector properties file provides a way to define the index name as concatenation of the topic name and message date.

"transforms": "TimestampRouter",
"transforms.TimestampRouter.topic.format": "${topic}-${timestamp}",
"transforms.TimestampRouter.timestamp.format": "yyyy-MM-dd",
"transforms.TimestampRouter.type": "org.apache.kafka.connect.transforms.TimestampRouter"

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The current version of the OpenSearch sink connector is not able to automatically create daily indices in OpenSearch. Therefore create the indices with the correct name before starting the sink connector. You can create OpenSearch indices in many ways including CURL commands.

Example: Create an OpenSearch® sink connector on a topic with a JSON schema

If you have a topic named iot_measurements containing the following data in JSON format, with a defined JSON schema:

{
    "schema": {
        "type":"struct",
        "fields":[{
            "type":"int64",
            "optional": false,
            "field": "iot_id"
            },{
            "type":"string",
            "optional": false,
            "field": "metric"
            },{
            "type":"int32",
            "optional": false,
            "field": "measurement"
            }]
    },
    "payload":{ "iot_id":1, "metric":"Temperature", "measurement":14}
}
{
    "schema": {
        "type":"struct",
        "fields":[{
            "type":"int64",
            "optional": false,
            "field": "iot_id"
            },{
            "type":"string",
            "optional": false,
            "field": "metric"
            },{
            "type":"int32",
            "optional": false,
            "field": "measurement"
            }]
    },
    "payload":{"iot_id":2, "metric":"Humidity", "measurement":60}}
}

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Since the JSON schema needs to be defined in every message, there is a big overhead to transmit the information. To achieve a better performance in term of information-message ratio you should use the Avro format together with the Karapace schema registry provided by Aiven

You can sink the iot_measurements topic to OpenSearch with the following connector configuration, after replacing the placeholders for OS_CONNECTION_URL, OS_USERNAME and OS_PASSWORD:

{
    "name":"sink_iot_json_schema",
    "connector.class": "io.aiven.kafka.connect.opensearch.OpensearchSinkConnector",
    "topics": "iot_measurements",
    "connection.url": "OS_CONNECTION_URL",
    "connection.username": "OS_USERNAME",
    "connection.password": "OS_PASSWORD",
    "type.name": "iot_measurements",
    "tasks.max":"1",
    "key.ignore": "true",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter"
}

The configuration file contains the following peculiarities:

"topics": "iot_measurements": setting the topic to sink
"value.converter": "org.apache.kafka.connect.json.JsonConverter": the message value is in plain JSON format without a schema
"key.ignore": "true": the connector is ignoring the message key (empty), and generating documents with ID equal to topic+partition+offset

Example: Create an OpenSearch® sink connector on a topic in plain JSON format

If you have a topic named students containing the following data in JSON format, without a defined schema:

Key: 1 Value: {"student_id":1, "student_name":"Carla"}
Key: 2 Value: {"student_id":2, "student_name":"Ugo"}
Key: 3 Value: {"student_id":3, "student_name":"Mary"}

You can sink the students topic to OpenSearch with the following connector configuration, after replacing the placeholders for OS_CONNECTION_URL, OS_USERNAME and OS_PASSWORD:

{
    "name":"sink_students_json",
    "connector.class": "io.aiven.kafka.connect.opensearch.OpensearchSinkConnector",
    "topics": "students",
    "connection.url": "OS_CONNECTION_URL",
    "connection.username": "OS_USERNAME",
    "connection.password": "OS_PASSWORD",
    "type.name": "students",
    "tasks.max":"1",
    "key.converter": "org.apache.kafka.connect.storage.StringConverter",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter",
    "value.converter.schemas.enable": "false",
    "schema.ignore": "true"
}

The configuration file contains the following peculiarities:

"topics": "students": setting the topic to sink
"key.converter": "org.apache.kafka.connect.storage.StringConverter": the message key is a string
"value.converter": "org.apache.kafka.connect.json.JsonConverter": the message value is in plain JSON format without a schema
"value.converter.schemas.enable": "false": since the data in the value doesn't have a schema, the connector shouldn't try to read it and sets it to null
"schema.ignore": "true": since the value schema is null, the connector doesn't infer it before pushing the data to OpenSearch

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The OpenSearch document ID is set as the message key

Elasticsearch is a trademark of Elasticsearch B.V., registered in the U.S. and in other countries.

Prerequisites​

Setup an OpenSearch sink connector with Aiven Console​

Define a Kafka Connect configuration file​

Create a Kafka Connect connector with the Aiven Console​

Create daily OpenSearch indices​

Example: Create an OpenSearch® sink connector on a topic with a JSON schema​

Example: Create an OpenSearch® sink connector on a topic in plain JSON format​

Prerequisites

Setup an OpenSearch sink connector with Aiven Console

Define a Kafka Connect configuration file

Create a Kafka Connect connector with the Aiven Console

Create daily OpenSearch indices

Example: Create an OpenSearch® sink connector on a topic with a JSON schema

Example: Create an OpenSearch® sink connector on a topic in plain JSON format