Struct Fallback 

pub struct Fallback<P, B> {
    pub primary: P,
    pub backup: B,
}

Primary for the chain, backup for old data.

Fields

primary: P

Decides head/finalized/headers; asked first for everything.

backup: B

Asked for a BAL body or a proof when the primary cannot serve it.

Implementations

impl<P, B> Fallback<P, B>

pub fn new(primary: P, backup: B) -> Self

Wrap primary with backup.

Trait Implementations

impl<P: BalSource, B: BalSource> BalSource for Fallback<P, B>

fn block<'life0, 'async_trait>( &'life0 self, number: u64, ) -> Pin<Box<dyn Future<Output = Result<SourcedBlock>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Header always from the primary; body from the primary, or from the backup if the primary has none. The archive verifies the body against this header, so a backup body is held to the primary’s chain.

fn head<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<u64>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Latest block number the source knows.

fn finalized<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<u64>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Latest finalized block number (reorg horizon).

fn header<'life0, 'async_trait>( &'life0 self, number: u64, ) -> Pin<Box<dyn Future<Output = Result<Header>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Header only. Used for reorg checks, where fetching the BAL would be wasted work; the default goes through BalSource::block.

fn bal<'life0, 'async_trait>( &'life0 self, number: u64, ) -> Pin<Box<dyn Future<Output = Result<BlockAccessList>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

BAL body only, unverified. Lets a backup supply the body while the header — the canonical-chain fact — still comes from the primary.

impl<P: StateSource, B: StateSource> StateSource for Fallback<P, B>

fn proof<'life0, 'life1, 'async_trait>( &'life0 self, addr: Address, slots: &'life1 [B256], block: u64, ) -> Pin<Box<dyn Future<Output = Result<AccountProof>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

eth_getProof(addr, slots, block). One call per (address, block) carries any number of slots — batching happens here, not in JSON-RPC.