oracle

Overview

Oracles provide blockchain applications access to off-chain information such as asset prices, and verifiable random numbers. Oracles allow blockchain applications to react to real-world events such as a price drop in collateral or the winner of a sporting event. Oracles typically rely on a trusted off-chain node to provide them with the correct data. This example oracle provides price data about a specific asset, and assumes a decimal precision of 1e9.

More information can be found in the specification.

Project structure

The project consists of an oracle smart contract and an oracle node which interacts with the oracle.

oracle
├── oracle-contract
│   ├── src/main.sw
│   └── tests/harness.rs
├── oracle-node
│   ├── src/main.rs
│   └── tests/harness.rs
├── README.md
└── SPECIFICATION.md

Running the project

User interface

TODO: The user interface does not currently exist.

Oracle node and contract

The project can be started by executing the following steps:

1. Change into the Oracle directory.

   cd <path>/sway-applications/oracle/<you are here>

2. Copy and paste the .env.example file into a new file called .env.

   cp project/oracle-node/.env.example project/oracle-node/.env

3. In the newly copied .env file there is a variable API_URL which ends with <your api key here>. This section should be replaced with your API key. You can read more about this project's environment variables here

4. Start a local fuel-core instance.

   fuel-core run --chain project/oracle-node/.chainConfig.json

   This spins up and configures the local fuel-core instance with the variables specified in .chainConfig.json.

5. Build the Oracle contract.

   forc build --locked

6. Deploy the Oracle contract.

   forc-deploy --path project/contracts/oracle-contract --node-url localhost:4000 --unsigned

   This will allow the node to interact with the oracle contract deployed to our local fuel-core instance.

   Note: Double check that the contract ID is the ID in the .env file.

7. Start the Oracle node.

   cargo run

Environment variables

Name	Description
API_URL	The URL the node uses to fetch the latest price for the asset tracked by the oracle. This oracle node relies on an external 3rd-party service to get price information to provide to the oracle contract. We do not endorse this service neither are we affiliated with them in any way. We only use the service for demonstration purposes. If you wish to run the node you can sign-up for a free api key here. If you wish to use another pricing api service feel free to replace API_URL entirely.
ORACLE_CONTRACT_ID	Deterministic contract id of the oracle contract deployed in step 5.
WALLET_SECRET	Private key of the first deterministic wallet provided by the fuels-rs sdk. This private key corresponds to the owner address specified in the oracle contract's Forc.toml. This address is also configured in step 4 to have the maximum amount of the BASE_ASSET.
FUEL_PROVIDER_URL	Fuel-core network url normally set as http://localhost:4000/graphql for development.

Project

In order to run the subsequent commands change into the following directory /path/to/oracle/<here>.

Program compilation

forc build --locked

Running the tests

Before running the tests the programs must be compiled with the command above.

cargo test --locked