Last Good Price Optimization

[dapp-whisperer]

Storing the lastGoodPrice in the priceFeed contract can be seen as redundant or undesirable in the setup with it as a primaryOracle of the ebtcFeed.

The priceFeed.lastGoodPrice() can also become out of date versus the EbtcFeed.lastGoodPrice().

So it could return success, with an outdated value vs the secondaryOracle on ebtcFeed.

• Change the PriceFeed to return failure (0) if it would return last good price.
• For valid prices: It should also just pass through price when storing a price rather than storing it as lastGoodPrice.

[rayeaster]

lastGoodPrice is a key state variable used in original PriceFeed design, especially when both its primary (like ChainLink) and secondary feed (like Tellor) are not working as expected.

If we skip storing an valid price to lastGoodPrice variable, existing logic in PriceFeed will be broken.

https://docs.google.com/spreadsheets/d/18fdtTUoqgmsK3Mb6LBO-6na0oK-Y9LWBqnPCJRp5Hsg/edit#gid=316701608

On the other hand, EbtcFeed could check both lastGoodPrice and status from PriceFeed to decide what to do with it. For example, if the status is bothOraclesUntrusted then EbtcFeed could choose to failover to its own secondaryOracle regardless of the lastGoodPrice returned by PriceFeed.

I think this might be the minimal disruptive way to move forward

[dapp-whisperer]

Agree here - we're invalidating the priceFeed as a standalone component.

if we consider the priceFeeds as one unit, it looks similar to above however. We "return the last good price of the parent EbtcFeed"

my inclination is to adapt all tests to the new setup and consider the priceFeeds as one unit

• Foundry suite
• Javascript suite
• PriceFeedTester & UnbiasedTester