A Sink Connector for Apache IoTDB

iotdb-kafka-sink-connector is a Sink connector for Apache IoTDB.

While Confluent Platform offers a diverse selection of connectors for Kafka services, an official Sink connector for integrating with IoTDB is currently not available (You can see official Kafka connectors here: https://docs.confluent.io/platform/current/connect/kafka_connectors.html).

This project is a simple example of implementing a minimal Kafka sink connector for integration with Apache IoTDB.

Dependencies:

• org.apache.kafka 0.11.0
• org.apache.iotdb 1.3.0
• org.slf4j 2.0.9

Build:

This project uses Maven as the build tools. To build it, run mvn package command. Example:

$ mvn clean package -P get-jar-with-dependencies

The 'get-jar-with-dependencies' profile, defined in the pom.xml file, packages the entire sink connector module into a single executable JAR file. The JAR file is compatible with confluent/kafka-connect service. After building, JAR file would be in the target directory.

---

Details:

A Sink connector primarily needs to inherit and extend three classes:

• org.apache.kafka.common.config.AbstractConfig
  • serves as a foundation for configuration management in custom connectors.
• org.apache.kafka.connect.sink.SinkTask
  • responsible for processing and sending data from Kafka topics to external systems (in this case SinkConnector object).
• org.apache.kafka.connect.sink.SinkConnector
  • serves as the blueprint for applications that move data from Kafka topics to external systems.

We also implemented an IoTDBSinkService class to isolate the code interacting with IoTDB from the main module.

We assume each Kafka message we consume has two required fileds:

• timestamp
• id

Consider a scenario where services publish messages to a Kafka topic named 'PV_DATA'. These messages, representing data from photovoltaic (PV) panels, could be formatted like this:

{
  'pv_id': 'dkJh1o0wxAM',
  'timestamp': 1709999058,
  'dc_power': 2.3,
  'irradiation': 4.67,
  'module_temperature': 16.8
}

Note that the message format can be PlainText, JSON, or Protobuf. Kafka-Connect handles decoding the message content automatically, so you don't need to concern yourself with the decoding stuff. For more detail about encoding and decondig Kafka messages see this. Schema-registry settings in the config file (iotdb-sink-config.json) is for this purpose.

---

Usage:

We've previously mentioned this SinkConnector is tested with the confluentinc/cp-kafka-connect Docker image. However, to integrate your custom iotdb-sink-connector, you'll need to take the following steps:

1. Build and Package the project to create a JAR file.

2. Mount the JAR file as a volume at /usr/share/java/ within the Kafka-Connect Docker container. (Example)

3. Prepare config file, you can use a file like iotdb-sink-config.json as a reference. This file provides an example of the settings required for the iotdb-kafka-sink-connector. (Note: AbstractConfig class reads the config file contents.)

4. Register the Sink connector. To register your custom connector you can send a POST request to Kafka-Connect REST service.

   $ curl -s -S -XPOST -H Accept:application/json -H Content-Type:application/json http://localhost:8083/connectors/ -d @./iotdb-sink-config.json

After registering the connector you can check it by tracing Kafka-Connect logs.

You can Unregister the connector using a DELETE request: $ curl -X DELETE http://localhost:8083/connectors/iotdb-sink-connector