`$currentDate`

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Definition

Syntax
Behavior
Examples

Definition

The $currentDate expression returns the system time of your stream processing instance each time Atlas Stream Processing evaluates it. This ensures that time fields you add from within a streaming data pipeline remain up-to-date for each processed message.

$currentDate: A $currentDate expression takes the form of an empty object {}.

Syntax

The $currentDate expression is an empty object {} and has no internal syntax.

Behavior

Pass $currentDate: {} as the value of any expression which accepts an ISODate value.

Examples

The following example demonstrates a basic use of the $currentDate expression to ensure accurate timestamps for each output document from a given stream processor.

{
  "$addFields": {
    "time1": {
      "$currentDate": {}
    }
  }
}

{
  "a": 1,
  "time1": ISODate("2025-01-24T11:57:22.033Z")
}

You can use the $currentDate expression multiple times in your stream processing pipeline to generate multiple timestamps for various stags within a stream processor.

{
  "$addFields": {
    "time1": {
      "$currentDate": {}
    }
  },
  "$group": {
    "_id": "$time1",
    "count": {
      "$count": {}
    }
  },
  "$addFields": {
    "time1": "$_id",
    "time2": {
      "$currentDate": {}
    }
  }
}

{
  "time1": ISODate("2025-01-24T11:57:22.033Z"),
  "time2": ISODate("2025-01-24T11:57:26.036Z"),
  "count": 1
}

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