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Design

Architecture

Compound is an implementation of MTG and a parachain of Mixin network.

  • The user transfers a payment(UTXO) that carries business data to the Mixin network.
  • Compound syncs the outputs(UTXO) by parsing the business data(in output.memo)
  • Compound dispatchs the business action(included in business data) and processes each action(supply, borrow...)

Code struct


---
|-cmd      
|-config  
|-deploy  
|-docs    
|-core 
|-pkg     
|-service 
|-store   
|-worker  
|-handler    
|-Dockerfile 
|-Makefile
|-main.go
  • cmd command entry, including start api server and worker and governance tools
  • config default config directory
  • docs project documents
  • core directory of project's models
  • pkg project packages that can be exported
  • service directory of business codes
  • store data repository(data may be stored in database or redis or memory cache)
  • worker directory for jobs that processing data in background
  • handler just for exported apis
  • Dockerfile for deployment
  • deploy store configs and tools of deployment
  • main.go
  • Makefile

configuration template

# genesis timestamp in second
genesis: 1603382400
location: Asia/Shanghai

db:
  dialect: mysql
  host: ~
  read_host: ~
  port: 3306
  user: ~
  password: ~
  database: ~
  location: Asia%2FShanghai
  debug: true

# It is recommended that each node configure its own price service
price_oracle:
  end_point: https://poracle-dev.fox.one

dapp:
  num: 7000103159
  client_id: ~
  session_id: ~
  client_secret: ~
  pin_token: ~
  pin: ""
  private_key: ~

group:
# private key shared by all nodes
  private_key: ~
  # The private key of the node user to sign the data
  sign_key: ~
  # node admins
  admins:
    - ~
    - ~
    - ~ 
  # all nodes
  members:
  # node id
    - client_id: ~
    # The public key used by the node to verify the signature
      verify_key: ~
  # multi-sign threshold
  threshold: 2

  vote:
    asset: 965e5c6e-434c-3fa9-b780-c50f43cd955c
    amount: 0.00000001

Rest APIs exported for application layer, including:

/markets   //response all markets
/markets/{asset} // response the market info of the specified asset
/liquidities/{address} //response user liquidities
/supplies //response supply datas
/borrows // response borrow datas
/transactions // response transactions

Worker

  • cashier Processes the pending transfers. prepare for transfering a transaction to Mixin network.
  • syncer Syncs the outputs(UTXO) from Mixin network.
  • txsender Transfers raw transaction to Mixin network.
  • spentsync syncs and updates the transfer state.
  • priceoracle Fetches a price and put the price on the chain.
  • payee processes outputs and dispatches business actions.

Action processing

  • borrow handles the borrow action event.
  • supply handles the supply action event.
  • pledge handles the pledge action event.
  • unpledge handles the unpledge action event.
  • redeem handles the redeem action event.
  • repay handles the repay action event.
  • liquidation handles the liquidation action event
  • proposal handles and dispatches the proposal actions, include: adding market, updating market, closing or opening market, adding or removing allowlist, withdraw
  • price handles the price protocal action event.

Market Trade-Curbing Mechanism

Close the market when the price of a certain market is abnormal.

  • When the price of a market is maliciously attacked, managers have the right to execute the close-market order and apply for a closed-market vote. If the request is approved, the market will be closed.
  • Trades are prohibited in closed markets.
  • However, as long as there are closed markets, liquidation of all markets will be prohibited, because liquidation will affect the liquidity of all market accounts of users.

The implementation of compound protocol

  • Interest rate model is The core implementation of compound protocol.

  • Borrow balance user borrow balance contains borrow principal and borrow interest. balance = borrow.principal * market.borrow_index / borrow.interest_index

  • Accrue interest Accruing interest only occurs when there is a behavior that causes changes in market transaction data, such as supply, borrow, pledge, unpledge, redeem, repay, price updating. And Only calculated once in the same block.

	blockNumberPrior := market.BlockNumber

	blockNum, e := s.blockSrv.GetBlock(ctx, time)
	if e != nil {
		return e
	}

	blockDelta := blockNum - blockNumberPrior
	if blockDelta > 0 {
		borrowRate, e := s.curBorrowRatePerBlockInternal(ctx, market)
		if e != nil {
			return e
		}

		if market.BorrowIndex.LessThanOrEqual(decimal.Zero) {
			market.BorrowIndex = borrowRate
		}

		timesBorrowRate := borrowRate.Mul(decimal.NewFromInt(blockDelta))
		interestAccumulated := market.TotalBorrows.Mul(timesBorrowRate)
		totalBorrowsNew := interestAccumulated.Add(market.TotalBorrows)
		totalReservesNew := interestAccumulated.Mul(market.ReserveFactor).Add(market.Reserves)
		borrowIndexNew := market.BorrowIndex.Add(timesBorrowRate.Mul(market.BorrowIndex))

		market.BlockNumber = blockNum
		market.TotalBorrows = totalBorrowsNew.Truncate(16)
		market.Reserves = totalReservesNew.Truncate(16)
		market.BorrowIndex = borrowIndexNew.Truncate(16)
	}