ReserveOracle

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Reserve oracles are used to determine the LST provider exchange rate and is utilizated by Ion's liquidation module. Liquidations will only be triggered against this exchange rate and will be completely market-price agnostic. Importantly, this means that liquidations will only be triggered through lack of debt repayment or slashing events.

In order to protect against potential provider bugs or incorrect one-off values (malicious or accidental), the reserve oracle does not use live data. Instead it will query the exchange every intermittent period and persist the value and this value can only move up or down by a maximum percentage per query. If additional data sources are available, they can be involved as FEEDs. If other FEEDs are provided to the reserve oracle, a mean of all the FEEDs is compared to the protocol exchange rate and the minimum of the two is used as the new exchange rate. This final value is subject to the bounding rules.

State Variables

ILK_INDEX

uint8 public immutable ILK_INDEX;

QUORUM

uint8 public immutable QUORUM;

MAX_CHANGE

uint256 public immutable MAX_CHANGE;

FEED0

IReserveFeed public immutable FEED0;

FEED1

IReserveFeed public immutable FEED1;

FEED2

IReserveFeed public immutable FEED2;

currentExchangeRate

uint256 public currentExchangeRate;

lastUpdated

uint256 public lastUpdated;

Functions

constructor

Creates a new ReserveOracle instance.

constructor(uint8 _ilkIndex, address[] memory _feeds, uint8 _quorum, uint256 _maxChange);

Parameters

Name	Type	Description
_ilkIndex	uint8	of the associated collateral.
_feeds	address[]	Alternative data sources to be used for the reserve oracle.
_quorum	uint8	The number of feeds to aggregate.
_maxChange	uint256	Maximum percent change between exchange rate updates. [RAY]

_getProtocolExchangeRate

Returns the protocol exchange rate.

Must be implemented in the child contract with LST-specific logic.

function _getProtocolExchangeRate() internal view virtual returns (uint256);

Returns

Name	Type	Description
<none>	uint256	The protocol exchange rate.

getProtocolExchangeRate

Returns the protocol exchange rate.

function getProtocolExchangeRate() external view returns (uint256);

Returns

Name	Type	Description
<none>	uint256	The protocol exchange rate.

_aggregate

Queries values from whitelisted data feeds and calculates the mean. This does not include the protocol exchange rate.

function _aggregate(uint8 _ILK_INDEX) internal view returns (uint256 val);

Parameters

Name	Type	Description
_ILK_INDEX	uint8	of the associated collateral.

_bound

Bounds the value between the min and the max.

function _bound(uint256 value, uint256 min, uint256 max) internal pure returns (uint256);

Parameters

Name	Type	Description
value	uint256	The value to be bounded.
min	uint256	The minimum bound.
max	uint256	The maximum bound.

_initializeExchangeRate

Intializes the currentExchangeRate state variable.

Called once during construction.

function _initializeExchangeRate() internal;

updateExchangeRate

Updates the currentExchangeRate state variable.

Takes the minimum between the aggregated values and the protocol exchange rate, then bounds it up to the maximum change and writes the bounded value to the state. NOTE: keepers should call this update to reflect recent values

function updateExchangeRate() external;

Events

UpdateExchangeRate

event UpdateExchangeRate(uint256 exchangeRate);

Errors

InvalidQuorum

error InvalidQuorum(uint8 invalidQuorum);

InvalidFeedLength

error InvalidFeedLength(uint256 invalidLength);

InvalidMaxChange

error InvalidMaxChange(uint256 invalidMaxChange);

InvalidMinMax

error InvalidMinMax(uint256 invalidMin, uint256 invalidMax);

InvalidInitialization

error InvalidInitialization(uint256 invalidExchangeRate);

UpdateCooldown

error UpdateCooldown(uint256 lastUpdated);