Event Time Assigner

Event Time Assigner Assembly (

) is used to assign an event time to each incoming record in a data stream.

In stream processing systems, event time represents the actual time when the event occurred, not the time when the system processed the event. This is important for accurate time-based analysis, such as window processing, event ordering, and late data handling.

The event time is assigned using a User Defined Function (UDF) Event Time Assigner.

Parameters of Event Time Assigner

There are two parameters in the Event Time Assigner Assembly.

Event Time Assigner Class
Specifies the class name of the Event Time Assigner used to determine the event time.
This class can be:
- A built-in Event Time Assigner
- A User Defined Event Time Assigner (UDF) created by the user
To create a custom class, follow the UDF plugin tutorial.
Example:
```
     com.labs247.function.CurrentTimeAssigner
```
Parameter
Specifies the parameter required by the Event Time Assigner class.
The meaning of the parameter depends on the selected class.
Example uses:
- Column index containing a timestamp
- Date-time format
- Custom parameter used by a user-defined class

Built-in Event Time Assigner Classes

HGrid247 provides three built-in Event Time Assigner classes.

CurrentTimeAssigner
Class:
```
    com.labs247.function.CurrentTimeAssigner
```
Description:
Assigns the current system time as the event time of the incoming record.

This method is typically used when:
- The data does not contain a timestamp field
- The processing time should be used as event time
Parameter:
Not required.
ColumnTimeMillisAssigner
Class:
```
    com.labs247.function.ColumnTimeMillisAssigner
```
Description:
Assigns the value of a column as the event time, where the column value is stored as milliseconds since epoch.
Parameter:
```
    column_index
```
Example:
```
    Parameter = 2
```
Meaning:
- Column 2 contains the timestamp value
- The value must be in milliseconds (long format)
Example data:
```
    id,user,time
    1,A,1700000000000
```
The value 1700000000000 will be used as the event time.

Default behavior:

If the parameter is empty, the default column index is 0.
ColumnFormatAssigner
Class:
```
    com.labs247.function.ColumnFormatAssigner
```
Description:
Assigns event time from a column containing a formatted date-time string.

The system converts the date-time string into a timestamp using the specified format.

Parameter format:
```
    column_index,date_format
```
Example:
```
Parameter = 2,yyyy-MM-dd HH:mm:ss
```
Meaning:
- Third Column contains a date string
- The format is yyyy-MM-dd HH:mm:ss
Example data:
```
    1,login,2025-02-07 14:35:00
```
The value 2025-02-07 14:35:00 will be parsed and used as the event time.

Default behavior:

If the parameter is empty:
```
    column_index = 0
    format = yyyy-MM-dd HH:mm:ss
```

Example Workflow

Example stream record:

    UserID | Action | EventTime

Example data:

    101 | login | 2026-02-07 10:15:30

Configuration:

    Event Time Assigner Class
    com.labs247.function.ColumnFormatAssigner

    Parameter
    2,yyyy-MM-dd HH:mm:ss

Result:

    Event Time = 2026-02-07 10:15:30

The system will use this value for time-based stream processing.

Summary

The Event Time Assigner Assembly is used to:

Assign event timestamps to stream records
Enable time-based stream processing
Support custom event-time logic via UDF

It supports three built-in methods:

Class                       Function
CurrentTimeAssigner         Uses the system processing time
ColumnTimeMillisAssigner    Uses a column with timestamp in milliseconds
ColumnFormatAssigner        Uses a column with formatted date-time

Supported Engines

Map Reduce	Spark 1.x RDD	Spark 2.x RDD	Spark 2.x Dataset	Apache Beam 2.29.0 Batch	Apache Beam 2.29.0 Streaming	Apache Flink 1.12.0 Batch	Apache Flink 1.12.0 Streaming	Apache Tez 0.9.1	PySpark

Number of input link	:	One
Number of output link	:	One