safe scheduler

[xlc]

similar to pallet-scheduler and implements the scheduler traits but using OCW to trigger & unsigned tx to execute

https://github.com/paritytech/substrate/blob/master/frame/support/src/traits/schedule.rs

this ensures a bad schedule won't brick the chain

https://github.com/paritytech/substrate/issues/8740#issuecomment-833212430

should be able to schedule calls after a timestamp or after a relaychain block number

[kianenigma]

But the doing this in OCW will imply totally different security guarantees. Is that acceptable?

Why is this an issue if you already have on-idle-scheduler somewhere?

cc @gpestana.

[xlc]

Yeah it cannot be a drop in replacement of pallet-scheduler. But for many use cases, OCW should be sufficient. We can have both pallet installed in a runtime and configure individually for each pallet on which scheduler to use.