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custom.javascript

Run custom JavaScript code.

Description​

A processor that makes it possible to process Conduit records using JavaScript.

The following helper functions and variables are available:

  • logger: a logger that outputs to Conduit's logs. Check out Zerolog's API on how to use it.
  • Record(): constructs a new record which represents a successful processing result. It's analogous to sdk.SingleRecord from Conduit's Go processor SDK.
  • RawData(): creates a raw data object. It's analogous to opencdc.RawData. Optionally, it accepts a string argument, which will be cast into a byte array, for example: record.Key = RawData("new key").
  • StructuredData(): creates a structured data (map-like) object.

To find out what's possible with the JS processor, also refer to the documentation for goja, which is the JavaScript engine we use.

Configuration parameters​

NameTypeDefaultDescription
scriptstring
null

JavaScript code for this processor. It needs to have a function process() that accept a record and returns a record. The process() function can either modify the input record and return it, or create a new record. If a record needs to be filtered (dropped from the pipeline), then the process() function should return null.

script.pathstring
null

The path to a .js file containing the processor code.

Examples​

Modify a record's metadata and payload using JavaScript​

In this example we use the custom.javascript processor to add a metadata key to the input record. It also prepends "hello, " to .Payload.After.

Configuration parameters​

NameValue
script
function process(rec) {
  rec.Metadata["processed"] = "true";
  let existing = String.fromCharCode.apply(String, rec.Payload.After);
  rec.Payload.After = RawData("hello, " + existing);
  return rec;
}
script.path
null

Record difference​

Before
After
1
{
1
{
2
  "position": null,
2
  "position": null,
3
  "operation": "Operation(0)",
3
  "operation": "Operation(0)",
4
  "metadata": {
4
  "metadata": {
5
-
    "existing-key": "existing-value"
5
+
    "existing-key": "existing-value",
6
+
    "processed": "true"
6
  },
7
  },
7
  "key": null,
8
  "key": null,
8
  "payload": {
9
  "payload": {
9
    "before": null,
10
    "before": null,
10
-
    "after": "world"
11
+
    "after": "hello, world"
11
  }
12
  }
12
}
13
}