Oracle module

Overview

Oracle module can be used to feed the system with off-chain data. e.g. a bot can query off-chain data from other sources and submit it into on-chain storage by calling oracle module.

It uses a trait called OperatorProvider::can_feed_data(who) to ensure someone have permission to submit data otherwise it will fail with error NoPermission. You can only submit updates once per block otherwise oracle will call OnRedundantCall::multiple_calls_per_block(&who) and fail with error UpdateAlreadyDispatched. The trait OnRedundantCall can be implemented to slash those who don't play by the roles, by default it does nothing.

Oracle module provides 2 public methods to submit data. Method feed_value is used to provide a single update and feed_values for batch updates. Keep in mind that you can call only one of them per block otherwise it will be a redundant call and fail. Both those methods are weight zero and dispatch class operational with a high priority, which means they can be misused to DoS the system, so be careful who you allow to call them and make sure to use CheckOperator to prevent multiple calls per block.

Module provides additional methods to read raw or combined data. CombineData provides a default implementation which finds a median from an array of valid values, but you can provide a custom implementation as well.