EDXCoalesce

Learn about the EDXCoalesce Edge Delta OTTL extension function.

  2 minute read  

Minimum Agent Version: v2.0.0

EDXCoalesce fills a gap in standard OTTL which lacks null coalescing capabilities. While OTTL can check for null values with IsMatch, it doesn’t provide an elegant way to select the first non-null value from multiple options. This Edge Delta extension works like the null coalescing operator (??) in modern languages, enabling graceful handling of missing or empty fields with a fallback value.

Syntax

EDXCoalesce(value, fallback)
  • value: The primary value or field reference to evaluate.
  • fallback: The fallback value or field reference to return if the primary value is null, empty, or zero.

For more than two values, nest multiple EDXCoalesce calls:

EDXCoalesce(value1, EDXCoalesce(value2, EDXCoalesce(value3, defaultValue)))

Input

{
  "_type": "log",
  "timestamp": 1735789600000,
  "body": "User activity log",
  "resource": {...},
  "attributes": {
    "user_id": null,
    "session_id": "",
    "tracking_id": "track-12345",
    "primary_email": null,
    "secondary_email": "",
    "fallback_email": "default@example.com",
    "error_message": "",
    "warning_message": null,
    "info_message": "Operation completed"
  }
}

Example

set(attributes["effective_id"], EDXCoalesce(attributes["user_id"], EDXCoalesce(attributes["session_id"], EDXCoalesce(attributes["tracking_id"], "anonymous"))))
set(attributes["contact_email"], EDXCoalesce(attributes["primary_email"], EDXCoalesce(attributes["secondary_email"], attributes["fallback_email"])))
set(attributes["log_message"], EDXCoalesce(attributes["error_message"], EDXCoalesce(attributes["warning_message"], EDXCoalesce(attributes["info_message"], "No message"))))

Output

{
  "_type": "log",
  "timestamp": 1735789630000,
  "body": "User activity log",
  "resource": {...},
  "attributes": {
    "user_id": null,
    "session_id": "",
    "tracking_id": "track-12345",
    "primary_email": null,
    "secondary_email": "",
    "fallback_email": "default@example.com",
    "error_message": "",
    "warning_message": null,
    "info_message": "Operation completed",
    "effective_id": "track-12345",
    "contact_email": "default@example.com",
    "log_message": "Operation completed"
  }
}

The EDXCoalesce function has selected the first non-null/non-empty value for each field: “track-12345” for the effective ID (skipping null user_id and empty session_id), “default@example.com” for the contact email (after checking primary and secondary), and “Operation completed” for the log message (after checking error and warning messages).