We get many number of requests in a queue. We are instantiating the workermanager work as and when we get any request. How does the ExistingWorkPolicy.REPLACE work?
Document says
If there is existing pending (uncompleted) work with the same unique name, cancel and delete it.
Will it also kill the existing running worker in the middle? We really do not want the existing worker to stop in the middle, it is ok to be replaced when the worker is enqueued but not in running state. Can we use REPLACE option here?
https://developer.android.com/reference/androidx/work/ExistingWorkPolicy
As explained in WorkManager's guide and in your question, when you enqueue a new UniqueWorkRequest using REPLACE as the existing worker policy, this is going to stop a previous worker that is currently running.
What happens to your worker really depends on how you implemented it (Worker, CoroutineWorker, or another ListenableWorker subclass) and how you handle stoppages and cancellations]2.
What this means, is that your Worker needs to "cooperatively" finish and cleanup your worker:
In the case of unique work, you explicitly enqueued a new WorkRequest with an ExistingWorkPolicy of REPLACE. The old WorkRequest is immediately considered terminated.
Under these conditions, your worker will receive a call to
ListenableWorker.onStopped(). You should perform cleanup and cooperatively finish your worker in case the OS decides to shut down your app.