Crate parachain_staking

Parachain Staking

A simple staking pallet providing means of selecting a set of collators to become block authors based on their total backed stake. The main difference between this pallet and frame/pallet-staking is that this pallet uses direct delegation. Delegators choose exactly who they delegate and with what stake. This is different from frame/pallet-staking where you approval vote and then run Phragmen. Moreover, this pallet rewards a collator and their delegators immediately when authoring a block. Rewards are calculated separately between collators and delegators.

To join the set of candidates, an account must call join_candidates with MinCollatorCandidateStake <= stake <= MaxCollatorCandidateStake.

To leave the set of candidates, the collator calls leave_candidates. If the call succeeds, the collator is removed from the pool of candidates so they cannot be selected for future collator sets, but they are not unstaking until executing the exit request by calling the extrinsic execute_leave_candidates at least ExitQueueDelay rounds later. After doing so, the collator candidate as well as their delegators are unstaked. Both parties then have to wait another StakeDuration more blocks to be able to unlock their stake.

Candidates which requested to leave can still be in the set of authors for the next round due to the design of the session pallet which at the start of session s(i) chooses a set for the next session s(i+1). Thus, candidates have to keep collating at least until the end of the next session (= round). We extend this by delaying their execute by at least ExitQueueDelay many sessions.

To join the set of delegators, an account must call join_delegators with stake >= MinDelegatorStake. There are also runtime methods for delegating additional collators and revoking delegations.

• Config
• Call
• Pallet

Overview

The KILT parachain staking pallet provides functions for:

• Joining the set of collator candidates of which the best MaxSelectedCandidates are chosen to become active collators for the next session. That makes the set of active collators the set of block authors by handing it over to the session and the authority pallet.
• Delegating to a collator candidate by staking for them.
• Increasing and reducing your stake as a collator or delegator.
• Revoking your delegation entirely.
• Requesting to leave the set of collator candidates.
• Withdrawing your unstaked balance after waiting for a certain number of blocks.

Terminology

• Candidate: A user which freezes up tokens to be included into the set of authorities which author blocks and receive rewards for doing so.

• Collator: A candidate that was chosen to collate this round.

• Delegator: A user which freezes up tokens for collators they trust. When their collator authors a block, the corresponding delegators also receive rewards.

• Total Stake: A collator’s own stake + the sum of delegated stake to this collator.

• Total collator stake: The sum of tokens locked for staking from all collator candidates.

• Total delegator stake: The sum of tokens locked for staking from all delegators.

• To Stake: Lock tokens for staking.

• To Unstake: Unlock tokens from staking.

• Round (= Session): A fixed number of blocks in which the set of collators does not change. We set the length of a session to the length of a staking round, thus both words are interchangeable in the context of this pallet.

• Freeze: A freeze on a specified amount of an account’s free balance until a specified block number. Multiple freezes always operate over the same funds, so they “overlay” rather than “stack”

Genesis config

The ParachainStaking pallet depends on the GenesisConfig.

Assumptions

• At the start of session s(i), the set of session ids for session s(i+1) are chosen. These equal the set of selected candidates. Thus, we cannot allow collators to leave at least until the start of session s(i+2).

Re-exports

• pub use crate::default_weights::WeightInfo;
• pub use crate::pallet::*;

Modules

• api
• benchmarking
  Benchmarking
• default_weights
  Autogenerated weights for parachain_staking
• pallet
  The pallet module in each FRAME pallet hosts the most important items needed to construct this pallet.