Feeds price feed oracles

Overview

The reference price (ETHUSD) for the Maker system is provided via an oracle (the medianizer), which collates price data from a number of external price feeds.

Price Feeds

Independent price feed operators constanly monitor the reference price across a number of external sources and will submit updates to the blockchain when:

1. Source price differs to the most recently submitted price by more than the defined amount (currently 1%)
2. Last price update was more than 6 hours ago.

Price updates are written to the blockchain via price feed contracts which are deployed and owned by feed operators. Price feed contracts which have been whitelisted by the medianizer are able to forward their prices for inclusion in the medianized price.

The Medianizer

The medianizer is the smart contract which provides Makers trusted reference price.

It maintains a whitelist of price feed contracts which are allowed to post price updates and a record of recent prices supplied by each address. Every time a new price update is received the median of all feed prices is re-computed and the medianized value is updated.

Permissions:

The adding and removal of whitelisted price feed addresses is controlled via governance, as is the setting of the min parameter - the minumum number of valid feeds required in order for the medianized value to be considered valid.