Integration Details
There are 2 ways of reading Umbrella on-chain data feeds:
- Direct Access: reading the data directly from the Umbrella feeds smart contract. This method has lower gas requirements.
- Via Reader: For those projects who need to integrate but cannot change their smart contract, they can read the data from the Umbrella Feeds Reader smart contracts. The Umbrella Feeds Reader connects to the Umbrella feeds smart contract. This method is more costly in terms of gas a it has one additional step compared to the Direct Access.
Prices are stored under a
key
.key
is constant, and it is the hash of the feed name (eg hash("UMB-USD") ).
Smart Contract hierarchy
Getting the address of the latest UmbrellaFeeds smart contract
Address of the lastest UmbrellaFeeds
smart contract can be resolved by using the Umbrella Registry
smart contract.
Addresses of the Umbrella Registry contracts for the different blockchains can be found in here.
Address can be resolved with the following method:
IRegistry.getAddress(bytes32("UmbrellaFeeds"))
Direct access
It is recommended option as it is the most gas effective.
The UmbrellaFeeds
smart contract is where all prices are submitted by the on-chain data feature of the Umbrella Oracle. Use getPriceData(key)
method to get price data about a specific key.
Price data structure contains:
struct PriceData {
uint8 data; // not in use, reserved for future
uint24 heartbeat; // if price is flat, how often it will be updated
uint32 timestamp; // last update
uint128 price; // 8 decimals
}
Via reader
There is the option to create dedicated contract reader which emulates interface of other leader oracles. As a first stage, we are implementing a contract with a Chainlink-like interface..
In order to instantiate a new Reader contract for a given data point:
- Go to
UmbrellaFeedsReaderFactory
smart contract and use thedeployed(key)
method to check whether there is already a Reader contract for your key. - if not, use the
UmbrellaFeedsReaderFactory.deploy(key)
method to create a new instance of the UmbrellaFeedsReader contract, dedicated for providedkey
.- Use
deployed(key)
method to read address of deployed contract. - In case contract code is not verified automatically, you can use (UmbrellaFeedsReader standard JSON)[./flattened/UmbrellaFeedsReader.stdandard.json] to verify its code.
- Use
UmbrellaFeedsReader provides few methods that you can use depending on the case:
latestRoundData()
: it follows chainlink interface to easier migration process from Chainlink to Umbrella.
IMPORTANT
Only
answer
andupdatedAt
field are in use.
getPriceData()
: it returns PriceData.
Fallback mechanism
A Fallback mechanism has been included in the Feeds smart contract to ensure you will be able to read data even if there is a new version of the Feeds smart contract.
Like a Proxy
While proxy contracts are forced to read implementation
address all the time, the fallback mechanism searches for a new address ONLY when it is needed, and only then, additional cost is added to the transaction.
Redeployments of contracts are very rare, so it is more effective to simply update contract address when needed than paying additional fee every time we read the price.
Updated 6 days ago