Module xcm_calls::staking[−][src]

Expand description

Xcm support for `pallet_staking` calls.

This module provides support for calling into the FRAME pallet_staking pallet of a remote chain via XCM.

Staking involves the bonding of funds for a certain amount of blocks.

The pallet_staking pallet is configured with the [Config::BondingDuration], the in number of eras that must pass until the funds can actually be removed (withdraw_unbonded), after they were unbonded.

An Era is defined as (whole) number of sessions, which is the period that the validator set (and each validator’s active nominator set) is recalculated and where rewards are paid out. An era is ~7 days (relay chain) and the BondingDuration on polkadot is 28 Eras and 7 Eras on Kusama.
A Session is a period of time that has a constant set of validators and is measured in block numbers. Sessions are handled by the FRAME pallet_session pallet which implement the ShouldEndSession trait which determines when a session has ended, and new started. This is used to determine the overall session length.

Kusama and polkadot rely on BABE (pallet_babe) to determine when a session has ended. the BABE pallet implements the ShouldEndSession trait and determines whether a session should end by determine whether the epoch should change. An epoch should change if more than EpochDuration time has passed. EpochDuration measures the amount of time in slots, that each epoch should last. An epoch length cannot be changed after the chain has started. Meaning this is chain specific constant. An Epoch on kusama is 1 hour, and 4 hours

Knowledge of the EpochDuration and the BondingDuration and the MILLISECS_PER_BLOCK or rather the SLOT_DURATION is required to determine when we call withdraw_unbonded after we initiate the unbond.