Add an index to the each split plugin event

[veyselkaraca]

Issue Description:

I would like to propose a new feature for the Logstash split plugin. Currently, when using the split plugin, there is no easy way to track the index or count of the split events generated from the original event. I suggest adding an index to each split plugin event to help users keep track of their position within the split events.

Use Case:

As a Logstash user, I recently encountered a situation where I needed to split a large event into multiple smaller events using the split plugin. However, I also needed to keep track of the index of each split event to perform specific operations or validations based on their position. Unfortunately, Logstash's split plugin does not provide this functionality, so I had to resort to complex workarounds to achieve my desired outcome.

Proposal:

I propose adding an 'index' field to each split event generated by the split plugin. This 'index' field would indicate the position of the split event within the series of split events. For example, if the original event is split into four smaller events, their 'index' values would be 1, 2, 3, and 4, respectively. This would greatly simplify tasks that require tracking the position of split events, such as conditional processing or logging.

Additional Context:

This feature enhancement would not only improve the usability of the split plugin but also make Logstash more versatile for various data processing scenarios. It would save users time and effort by eliminating the need for custom solutions to track split event positions.