Crate sc_client

Substrate Client and associated logic.

The Client is one of the most important components of Substrate. It mainly comprises two parts:

• A database containing the blocks and chain state, generally referred to as the Backend.
• A runtime environment, generally referred to as the Executor.

Initialization

Creating a Client is done by calling the new method and passing to it a Backend and an Executor.

The former is typically provided by the sc-client-db crate.

The latter typically requires passing one of:

• A LocalCallExecutor running the runtime locally.
• A RemoteCallExecutor that will ask a third-party to perform the executions.
• A RemoteOrLocalCallExecutor, combination of the two.

Additionally, the fourth generic parameter of the Client is a marker type representing the ways in which the runtime can interface with the outside. Any code that builds a Client is responsible for putting the right marker.

Example

use std::sync::Arc;
use sc_client::{Client, in_mem::Backend, LocalCallExecutor};
use sp_runtime::Storage;
use sc_executor::{NativeExecutor, WasmExecutionMethod};

// In this example, we're using the `Block` and `RuntimeApi` types from the
// `substrate-test-runtime-client` crate. These types are automatically generated when
// compiling a runtime. In a typical use-case, these types would have been to be generated
// from your runtime.
use substrate_test_runtime_client::{LocalExecutor, runtime::Block, runtime::RuntimeApi};

let backend = Arc::new(Backend::<Block>::new());
let client = Client::<_, _, _, RuntimeApi>::new(
	backend.clone(),
	LocalCallExecutor::new(
		backend.clone(),
		NativeExecutor::<LocalExecutor>::new(WasmExecutionMethod::Interpreted, None, 8),
        sp_core::tasks::executor(),
	),
	// This parameter provides the storage for the chain genesis.
	&<Storage>::default(),
	Default::default(),
	Default::default(),
	Default::default(),
	None,
);

Re-exports

pub use sc_client_api::blockchain;

pub use crate::leaves::LeafSet;

Modules

cht	Canonical hash trie definitions and helper functions.
genesis	Tool for creating the genesis block.
in_mem	In memory client backend
leaves	Helper for managing the set of available leaves in the chain for DB implementations.
light	Light client components.
utils	Utility methods for the client.
well_known_cache_keys	A list of all well known keys in the blockchain cache.

Structs

BlockImportNotification	Summary of an imported block
ChainInfo	Blockchain info
Client	Substrate Client
ClientInfo	Client info
ExecutionStrategies	Execution strategies settings.
FinalityNotification	Summary of a finalized block.
LocalCallExecutor	Call executor that executes methods locally, querying all required data from local backend.
LongestChain	Implement Longest Chain Select implementation where 'longest' is defined as the highest number of blocks
StateMachine	The substrate state machine.
StorageChangeSet	Storage change set
StorageProof	A proof that some set of key-value pairs are included in the storage trie. The proof contains the storage values so that the partial storage backend can be reconstructed by a verifier that does not already have access to the key-value pairs.

Enums

ExecutionStrategy

Strategy for executing a call into the runtime.

Traits

BlockBackend	Interface for fetching block data.
BlockOf	Figure out the block type for a given type (for now, just a Client).
BlockchainEvents	A source of blockchain events.
CallExecutor	Method call executor.
LockImportRun	Interface for performing operations on the backend.
ProvideUncles	Provide a list of potential uncle headers for a given block.

Functions

apply_aux	Helper function to apply auxiliary data insertion into an operation.
new_in_mem	Create an instance of in-memory client.
new_with_backend	Create a client with the explicitly provided backend. This is useful for testing backend implementations.

Type Definitions

BadBlocks	Known bad block hashes.
FinalityNotifications	A stream of block finality notifications.
ForkBlocks	Expected hashes of blocks at given heights.
ImportNotifications	Type that implements futures::Stream of block import events.
StorageEventStream	Type that implements futures::Stream of storage change events.