How to Clean Staking System?

[aurexav]

The withdraw_unbonded was removed.

How to trigger the kill_stash to remove the 'empty' account and keep the staking system clean?

StakingLedger {
	active_ring/kton: zero,
	ring/kton_lock: all expired,
	...
}

[yanganto]

The kill_stash is called on the account has zero balance(on_free_balance_zero), or the dust account has every low free balance(on_free_too_low).

[yanganto]

The bond do two things

• let two accounts has roles, stash and controller
• some values(Ring and Kton) are locked.

And the unbond process only do one thing

• free the lock of some values

There is not an easy way to clear the relation between stash and controller.
The relation between stash and controller exist, the staking ledge may be still existed for clarity.
If we want to remove staking ledge to shrink the storage in the future blocks,
we need some way to break the relation between of stash and controller.

Here is the proposal.
In the unbond process, some values unlock.
Once there are none values locked, the relation between stash and control will be break,
and these account will become normal accounts,
such that the staking ledge can be removed to save the storage.

Besides, the user still can use bond_extra to bond more values to keep the bonded accounts.

[aurexav]

• origin logic:
  • https://github.com/darwinia-network/substrate/blob/darwinia-develop/srml/staking/src/lib.rs#L783
  • https://github.com/darwinia-network/substrate/blob/darwinia-develop/srml/staking/src/lib.rs#L842

[yanganto]

The original operations of Substrate are unbond and withdraw_unbond. We can just let this process more smart. People can unbond to free the lock of values, and it will be auto withdraw when there is no value locked.