0g-chain/x/cdp/spec/04_begin_block.md
Ruaridh e11b298c28 Add CDP Spec (#328)
* add overview and basic structure

* add state and params

* add basic messages

* add state transitions

* add begin block state transitions

* add missing titles

* add concepts

* add events

* update state and concepts

* update for liquidator changes

* update events

* mention module accounts

* update begin block

* update params

* update page numbering

* add fee descriptions

* add broken link linter

* add broken link linter to CI

* move link check to end of CI

* update typo

Co-Authored-By: Kevin Davis <karzak@users.noreply.github.com>

* address review comments

* Update x/cdp/spec/06_params.md

Co-Authored-By: Kevin Davis <karzak@users.noreply.github.com>

* Update x/cdp/spec/README.md

Co-Authored-By: Kevin Davis <karzak@users.noreply.github.com>

* Update x/cdp/spec/README.md

Co-Authored-By: Kevin Davis <karzak@users.noreply.github.com>

Co-authored-by: Kevin Davis <karzak@users.noreply.github.com>
2020-01-23 14:09:36 -05:00

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Markdown

# Begin Blocker
At the start of every block the BeginBlocker of the cdp module:
- updates total CDP fees
- liquidates CDPs under the collateral ratio
- nets out system debt and, if necessary, starts auctions to re-balance it
- records the last block time
## Update Fees
- The total fees accumulated since the last block across all CDPs are calculated.
- 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
## Liquidate CDP
- Get every cdp that is under the liquidation ratio for its collateral type.
- For each cdp:
- Calculate and update fees since last update.
- 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 remaining for an auction, start one.
- Otherwise do nothing, leave debt/surplus to accumulate over subsequent blocks.
## Update Previous Block Time
The current block time is recorded.