0g-chain/x/cdp/spec/06_begin_block.md

Begin Block

At the start of every block the BeginBlock of the cdp module:

• updates the status of the pricefeed for each collateral asset
• If the pricefeed is active (reporting a price):
  • updates fees for CDPs
  • liquidates CDPs under the collateral ratio
• nets out system debt and, if necessary, starts auctions to re-balance it
• pays out the savings rate if sufficient time has past
• records the last savings rate distribution, if one occurred

Update Fees

• The total fees accumulated since the last block for each CDP are calculated.
• If the fee amount is non-zero:
  • Set the updated value for fees
  • Set the fees updated time for the CDP to the current block time
  • An equal amount of debt coins are minted and sent to the system's CDP module account.
  • An equal amount of stable asset coins are minted and sent to the system's liquidator module account
  • Increment total principal.

Liquidate CDP

• Get every cdp that is under the liquidation ratio for its collateral type.
• For each cdp:
  • Remove all collateral and internal debt coins from cdp and deposits and delete it. Send the coins to the liquidator module account.
  • Start auctions of a fixed size from this collateral (with any remainder in a smaller sized auction), sending collateral and debt coins to the auction module account.
  • Decrement total principal.

Net Out System Debt, Re-Balance

• Burn the maximum possible equal amount of debt and stable asset from the liquidator module account.
• If there is enough debt remaining for an auction, start one.
• If there is enough surplus stable asset, minus surplus reserved for the savings rate, remaining for an auction, start one.
• Otherwise do nothing, leave debt/surplus to accumulate over subsequent blocks.

Distribute Surplus Stable Asset According to the Savings Rate

• If SavingsDistributionFrequency seconds have elapsed since the previous distribution, the savings rate is applied to all accounts that hold stable asset.
• Each account that holds stable asset is distributed a ratable portion of the surplus that is apportioned to the savings rate.
• If distribution occurred, the time of the distribution is recorded.