Responsibilities of the Oracle:
- Spinning up the necessary services (e.g. the sidecar, the price fetchers, etc.).
- Managing the lifecycle of the providers.
- Determining the set of markets that need to be fetched and updating the providers accordingly.
At a high level the oracle is configured with a oracle.json file that contains all providers that need to be instantiated. To read more about the configuration of oracle.json, please refer to the oracle configuration documentation.
Each provider is instantiated using the PriceAPIQueryHandlerFactory, PriceWebSocketQueryHandlerFactory, and MarketMapFactory factory functions. Think of these as the constructors for the providers.
PriceAPIQueryHandlerFactory- This is used to create the API query handler for the provider - which is then passed into a base provider.PriceWebSocketQueryHandlerFactory- This is used to create the WebSocket query handler for the provider - which is then passed into a base provider.MarketMapFactory- This is used to create the market map provider.
The oracle can be initialized with an option of WithMarketMap which allows each provider to be instantiated with a predetermined set of markets. If this option is not provided, the oracle will fetch the markets from the market map provider. Both options can be set.
The oracle will then start each provider in a separate goroutine. Additionally, if the oracle has a market map provider, it will start a goroutine that will periodically fetch the markets from the market map provider and update the providers accordingly.
All providers are running concurrently and will do so until the main context is canceled (what is passed into Start). If the oracle is canceled, it will cancel all providers and wait for them to finish before returning.