Create a stream reactor sink connector from Apache Kafka® to Redis®*
The Redis stream reactor sink connector enables you to move data from an Aiven for Apache Kafka® cluster to a Redis®* database. The Lenses.io implementation enables you to write KCQL transformations on the topic data before sending it to the Redis database.
A known issue with the GEOADD
command in version 4.2.0 of the Redis
stream reactor sink connector may cause exceptions during initialization
under specific configurations. For more information, see the GitHub
issue.
See the full set of available parameters and configuration options in the connector's documentation.
Prerequisites
To setup a Redis 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 Redis database upfront:
-
REDIS_HOSTNAME
: The Redis hostname -
REDIS_PORT
: The Redis port -
REDIS_PASSWORD
: The Redis password -
REDIS_SSL
: The Redis SSL setting, should betrue
orfalse
-
TOPIC_LIST
: The list of topics to sink divided by comma -
KCQL_TRANSFORMATION
: The KCQL syntax to parse the topic data, should be in the format:[INSERT INTO REDIS_CACHE] SELECT LIST_OF_FIELDS FROM APACHE_KAFKA_TOPIC
-
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
If you're using Aiven for Caching 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 a Redis sink connector with Aiven Console
The following example demonstrates how to setup a Redis 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 redis_sink.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:
{
"name":"CONNECTOR_NAME",
"connector.class": "com.datamountaineer.streamreactor.connect.redis.sink.RedisSinkConnector",
"topics": "TOPIC_LIST",
"connect.redis.host": "REDIS_HOSTNAME",
"connect.redis.port": "REDIS_PORT",
"connect.redis.password": "REDIS_PASSWORD",
"connect.redis.ssl.enabled": "REDIS_SSL",
"connect.redis.kcql": "KCQL_TRANSFORMATION",
"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, replaceCONNECTOR_NAME
with the name to use for the connector.connect.redis.*
: sink parameters collected in the prerequisite phase.key.converter
andvalue.converter
: defines the messages data format in the Apache Kafka topic. Theio.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 theschema.registry.url
parameter and related credentials.
The key.converter
and value.converter
sections define how the topic
messages will be parsed and needs to be included in the connector
configuration.
When using Avro as source data format, to set following parameters
value.converter.schema.registry.url
: pointing to the Aiven for Apache Kafka schema registry URL in the form ofhttps://APACHE_KAFKA_HOST:SCHEMA_REGISTRY_PORT
with theAPACHE_KAFKA_HOST
andSCHEMA_REGISTRY_PORT
parameters retrieved in the previous step.value.converter.basic.auth.credentials.source
: to the valueUSER_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 ofSCHEMA_REGISTRY_USER:SCHEMA_REGISTRY_PASSWORD
with theSCHEMA_REGISTRY_USER
andSCHEMA_REGISTRY_PASSWORD
parameters retrieved in the previous step.
Create a Kafka Connect connector with the Aiven Console
To create an Apache 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, this is enabled only for services with Kafka Connect enabled.
-
Select Stream Reactor Redis Sink.
-
In the Common tab, locate the Connector configuration text box and select on Edit.
-
Paste the connector configuration (stored in the
redis_sink.json
file) in the form. -
Select Apply.
noteThe 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 Redis service.
You can also create connectors using the Aiven CLI command.
Example: Create a Redis sink connector
If you have a topic named students
containing the following data that
to move to Redis:
{"id":1, "name":"carlo", "age": 77}
{"id":2, "name":"lucy", "age": 55}
{"id":3, "name":"carlo", "age": 33}
{"id":2, "name":"lucy", "age": 21}
You can sink the students
topic to Redis with the following connector
configuration, after replacing the placeholders for REDIS_HOST
,
REDIS_PORT
, REDIS_DB_NAME
, REDIS_USERNAME
and REDIS_PASSWORD
:
{
"name": "my-redis-sink",
"connector.class": "com.datamountaineer.streamreactor.connect.redis.sink.RedisSinkConnector",
"connect.redis.host": "REDIS_HOSTNAME",
"connect.redis.port": "REDIS_PORT",
"connect.redis.password": "REDIS_PASSWORD",
"connect.redis.ssl.enabled": "REDIS_SSL",
"topics": "students",
"value.converter": "org.apache.kafka.connect.json.JsonConverter",
"value.converter.schemas.enable": "false",
"connect.redis.kcql": "INSERT INTO students- SELECT * FROM students PK id"
}
The configuration file contains the following peculiarities:
"topics": "students"
: setting the topic to sink"connect.redis"
: the connection parameters placeholders"value.converter": "org.apache.kafka.connect.json.JsonConverter"
and"value.converter.schemas.enable": "false"
: the topic value is in JSON format without a schema"connect.redis.kcql": "INSERT INTO students- SELECT * FROM students PK id"
: the connector logic is to insert every topic message as new entry in Redis, using theid
field as key prefixed withstudents-
(configured in theINSERT INTO
statement).
Once the connector is created successfully, you should see the following three entries in the target Redis database.
1. "students-1" containing "{\"name\":\"carlo\",\"id\":1,\"age\":77}"
2. "students-2" containing "{\"name\":\"lucy\",\"id\":2,\"age\":21}"
3. "students-3" containing "{\"name\":\"carlo\",\"id\":3,\"age\":33}"
There are only three keys in Redis since there were two messages in the
topic sharing the "id": 2
, and the connector will overwrite entries
sharing the same key.