pezkuwi-subxt/polkadot/roadmap/implementers-guide/src/node/utility/runtime-api.md

Runtime API

The Runtime API subsystem is responsible for providing a single point of access to runtime state data via a set of pre-determined queries. This prevents shared ownership of a blockchain client resource by providing

Protocol

Input: RuntimeApiMessage

Output: None

Functionality

On receipt of RuntimeApiMessage::Request(relay_parent, request), answer the request using the post-state of the relay_parent provided and provide the response to the side-channel embedded within the request.

TODO Do some caching. The underlying rocksdb already has a cache of trie nodes so duplicate requests are unlikely to hit disk. Not required for functionality.

Jobs

TODO Don't limit requests based on parent hash, but limit caching. No caching should be done for any requests on relay_parents that are not active based on ActiveLeavesUpdate messages. Maybe with some leeway for things that have just been stopped.