Spot - Detailed Documentation
The Maker Protocol's liaison between the Oracles and Core Contracts
Last updated
The Maker Protocol's liaison between the Oracles and Core Contracts
Last updated
Contract Name: spot.sol
Type/Category: DSS —> Core Module
The Spot
liaison between the oracles
and the core contracts. It functions as an interface contract and only stores the current ilk
list.
All mathematical operations will revert on overflow or underflow
All methods execute in constant time
ilk
a given collateral type
ilk.pip
the contract which holds the current price of a given ilk
ilk.mat
the liquidation ratio for a given ilk
vat
the core of the mcd system
par
value of DAI in the reference asset (e.g. $1 per DAI)
Only authorized users can update any variables in contract
poke
is the only non-authenticated function in spot
. The function takes in a bytes32
of the ilk
to be "poked". poke
calls two external
functions:
peek
calls the OSM for the given ilk
and takes back in the val
and has
(a boolean which is false if there was an error in the osm
). The second external call only happens if has == true
.
When calculating the spot
, the par
is crucial to this calculation as it defines the relationship between DAI and 1 unit of value in the price. The val
is then divided by the par
(to get a ratio of val
to DAI
) and then the resulting value is divided by the ilk.mat
. This gives us the current spot
price for the given ilk
.
file
is then called after calculating the spot
. This updates the vat
with the current liquidation price of the ilk
which the function was called for.
The methods in the spotter
are relatively basic compared to most other portions of dss
. There is not much room for user error in the single unauthed method poke
. If an incorrect bytes32
is supplied the call will fail.
Any module that is authed against the spot
has full root access, and can, therefore, add and remove which ilks
can be "poked". While not completely breaking the system, this could cause considerable risk.
A bug in spot
would most likely result in the prices for collaterals not being updated anymore. In this case, the system would need to authorize a new spot
which would then be able to update the prices. Overall this is not a catastrophic failure as this would only pause all price fluctuation for some period.
The spot
relies upon a set of trusted oracles to provide price data. Should these price feeds fail, it would become possible for unbacked Dai to be minted, or safe Vaults could be unfairly liquidated.
When poke
is not called frequently enough, the Vat
's spot
price will become stale. This could arise for a few reasons including tragedy of the commons or miner collusion and could lead to negative outcomes such as inappropriate liquidations, or the prevention of liquidations that should be possible.