How to move event time forward using externally generated watermark message

Posted by Manas Kale on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/How-to-move-event-time-forward-using-externally-generated-watermark-message-tp33844.html

Hi,

I have a scenario where I have an input event stream from various IoT devices. Every message on this stream can be of some eventType and has an eventTimestamp. Downstream, some business logic is implemented on this based on event time.

In case a device goes offline, what's the best way to indicate to this system that even time has progressed? Should I : 

• Send a special message that contains only event time information, and write code to handle this message in all downstream operators?

• Implement some processing time timer in the system that will tick the watermark forward if we don't see any message for some duration? I will still need to write code in downstream operators that handles this timer's trigger message.

I would prefer not writing code to handle special watermark messages. So does Flink provide any API level call that I can use to tick the watermark forward for all downstream operators when this special message is received / timer is fired?