Kafka Connect JSLT Single Message Transform

Last update: May 25, 2022

Overview

Kafka Connect JSLT Single Message Transform

This is an implementation of the Kafka Connect SMT interface to offer transformation capabilities using the Schibsted JSLT library.

Build

The library uses Gradle to build the JAR.

Install latest Java SDK.
Checkout the Git repository and change to its root folder.
Execute ./gradlew build

The JAR can then be found in the build/libs/ subfolder.

Install

After the JAR was build as described above, copy it to your Kafka Connect instance into one of the directories listed in the plugin.path property in the connect worker configuration file.

Make sure to do this on all Kafka Connect worker nodes!

See the Confluent Kafka Connect Plugins Userguide for more details.

Usage

Connector Configuration

The transformer expects the jslt attribute in the connector config JSON. In the following example the dot means it will not perform any transformation but this string can be any valid JSLT expression.

Note that Json does not support multiline strings. So linebreaks and quotes must be escaped with a backslash (e.g. " -> \")

{
  "name": ...,
  "config": {
    ...,
    "transforms": "jsltTransform",
    "transforms.jsltTransform.type": "at.willhaben.kafka.connect.transforms.jslt.JsltTransform$Value",
    "transforms.jsltTransform.jslt": "."
  }
}

Note that the transformer only supports some kind of structured input. So make sure that there is a converter class (e.g. AvroConverter, JsonConverter) like "value.converter": "io.confluent.connect.avro.AvroConverter" that provides the data in a structured format.

The following links are helpful to learn more about JSLT:

JSLT Tutorial and Examples: examples of the JSLT language features
JSLT Function Reference: Documentation of the included functions
JSLT Demo Playground: comes in handy to try out the logic

Example JSLT

The following JSLT takes a nested structure as input and

adds a new constant field producer_team
maps the values of the field customer_status from a numeric representation to a code, using custom logic
pseudonymizes the customer_id field
adds a list of objects field locations based on the separate invoice/delivery address fields of the input
extracts and flattens the two attributes customer_type and customer_class

Input Record

{
  "cusomer_id": 123456,
  "customer_status": 2,
  "invoice_address_street": "McDuck Manor",
  "invoice_address_zip_code": "1312",
  "invoice_address_city": "Duckburg",
  "delivery_address_street": "Webfoot Walk",
  "delivery_address_zip_code": "1313",
  "delivery_address_city": "Duckburg",
  "attributes": {
    "customer_type": "C2C",
    "customer_class": "A",
    "last_order": "2022-03-10T18:25:43.511Z"
  }
}

JSLT

{
  def map_status(status)
  if ($status == 0)
    "ACTIVE"
  else if ($status == 1)
    "INACTIVE"
  else
    "UNDEFINED"

  "customer_id": sha256-hex(.customer_id),
  "customer_status_code": map_status(.customer_status),
  "locations": [
    {
      "zip_code": .invoice_address_zip_code,
      "city": .invoice_address_city
    },
    {
      "zip_code": .delivery_address_zip_code,
      "city": .delivery_address_city
    }
  ],
  "customer_type": .attributes.customer_type,
  "customer_class": .attributes.customer_class,
  "producer_team": "us.california.burbank.disney"
}

Output Record

{
  "customer_id": "8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92",
  "customer_status_code": "INACTIVE",
  "locations": [
    {
      "zip_code": "1312",
      "city": "Duckburg"
    },
    {
      "zip_code": "1313",
      "city": "Duckburg"
    }
  ],
  "customer_type": "C2C",
  "customer_class": "A",
  "producer_team": "us.california.burbank.disney"
}

Additional Notes

The JSLT library works with the JsonNode class to perform the transformation.

This class uses quite generic data types and the conversion to/from JsonNode could lead to some changes in the returned datatype. This might especially an issue with floating point values!

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Comments

Option to Mark Fields as Mandatory

Firstly a quick thanks. After struggling with the SMTs currently on offer.. JSLT for Kafka Connectors is the silver bullet addressing most of our needs. All except for this one remaining issue; all fields produced by the transform are set as optional in the Schema Registry (we're using AVRO).

Ideally the optional state of fields would be configurable and would work something like Confluent's InsertField SMT which lets you mark fields as mandatory by suffixing the field name with a ! - see InsertField.

opened by albp-rmt 1

Kafka Connect JSLT Single Message Transform

Related tags

Overview

Kafka Connect JSLT Single Message Transform

Build

Install

Usage

Connector Configuration

Example JSLT

Additional Notes

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Comments

Option to Mark Fields as Mandatory

Releases(1.1.0)

1.1.0(Jun 1, 2022)

1.0.1(May 22, 2022)

1.0.0(Mar 18, 2022)

Owner

willhaben

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