Struct HandoffReader 

pub struct HandoffReader<T> { /* private fields */ }

Reads locator handoff records from block storage.

Each poll call reads the block lease, deserializes the handoff state, and returns Some(state) if the generation has changed since the last successful poll.

Fail-closed

If the block data is corrupt or deserialization fails, poll returns an error — never a stale or default value.

Example

use grafos_locator::handoff::HandoffReader;
use grafos_locator::locator::QueueLocator;
use grafos_std::block::BlockBuilder;

let lease = BlockBuilder::new().acquire().unwrap();
let mut reader: HandoffReader<QueueLocator> = HandoffReader::new(lease);
match reader.poll() {
    Ok(Some(state)) => println!("new locator: {:?}", state.locator),
    Ok(None) => println!("no change"),
    Err(e) => println!("read error: {e}"),
}

Implementations

impl<T: Serialize + DeserializeOwned + Clone> HandoffReader<T>

pub fn new(block_lease: BlockLease) -> Self

Create a new handoff reader attached to the given block lease.

pub fn poll(&mut self) -> Result<Option<HandoffState<T>>>

Poll the block storage for a new handoff state.

Returns Ok(Some(state)) if the generation has changed since the last successful poll, Ok(None) if unchanged, or Err on I/O or deserialization failure.

pub fn changed(&self) -> bool

Returns true if the last poll returned a new generation.

pub fn last_generation(&self) -> Option<FenceEpoch>

Returns the last generation seen by poll, if any.

pub fn last_locator(&self) -> Option<&T>

Returns a reference to the last locator seen by poll, if any.