Implementation of the new validator disabling strategy (#2226)
Closes https://github.com/paritytech/polkadot-sdk/issues/1966, https://github.com/paritytech/polkadot-sdk/issues/1963 and https://github.com/paritytech/polkadot-sdk/issues/1962. Disabling strategy specification [here](https://github.com/paritytech/polkadot-sdk/pull/2955). (Updated 13/02/2024) Implements: * validator disabling for a whole era instead of just a session * no more than 1/3 of the validators in the active set are disabled Removes: * `DisableStrategy` enum - now each validator committing an offence is disabled. * New era is not forced if too many validators are disabled. Before this PR not all offenders were disabled. A decision was made based on [`enum DisableStrategy`](https://github.com/paritytech/polkadot-sdk/blob/bbb66316/substrate/primitives/staking/src/offence.rs#L54). Some offenders were disabled for a whole era, some just for a session, some were not disabled at all. This PR changes the disabling behaviour. Now a validator committing an offense is disabled immediately till the end of the current era. Some implementation notes: * `OffendingValidators` in pallet session keeps all offenders (this is not changed). However its type is changed from `Vec<(u32, bool)>` to `Vec<u32>`. The reason is simple - each offender is getting disabled so the bool doesn't make sense anymore. * When a validator is disabled it is first added to `OffendingValidators` and then to `DisabledValidators`. This is done in [`add_offending_validator`](https://github.com/paritytech/polkadot-sdk/blob/bbb66316/substrate/frame/staking/src/slashing.rs#L325) from staking pallet. * In [`rotate_session`](https://github.com/paritytech/polkadot-sdk/blob/bdbe9829/substrate/frame/session/src/lib.rs#L623) the `end_session` also calls [`end_era`](https://github.com/paritytech/polkadot-sdk/blob/bbb66316/substrate/frame/staking/src/pallet/impls.rs#L490) when an era ends. In this case `OffendingValidators` are cleared **(1)**. * Then in [`rotate_session`](https://github.com/paritytech/polkadot-sdk/blob/bdbe9829/substrate/frame/session/src/lib.rs#L623) `DisabledValidators` are cleared **(2)** * And finally (still in `rotate_session`) a call to [`start_session`](https://github.com/paritytech/polkadot-sdk/blob/bbb66316 /substrate/frame/staking/src/pallet/impls.rs#L430) repopulates the disabled validators **(3)**. * The reason for this complication is that session pallet knows nothing abut eras. To overcome this on each new session the disabled list is repopulated (points 2 and 3). Staking pallet knows when a new era starts so with point 1 it ensures that the offenders list is cleared. --------- Co-authored-by:ordian <[email protected]> Co-authored-by:
ordian <[email protected]> Co-authored-by:
Maciej <[email protected]> Co-authored-by:
Gonçalo Pestana <[email protected]> Co-authored-by:
Kian Paimani <[email protected]> Co-authored-by: command-bot <> Co-authored-by:
Ankan <[email protected]>