Struct Durable

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

Expand description

A wrapper that checkpoints its inner value to block storage.

Durable<T> owns both the inner value and a BlockLease used for persistence. Calling checkpoint() serializes the inner value and writes it to the block lease. restore() reads a checkpoint and reconstructs the value.

Implements Deref<Target = T> and DerefMut, so you can access the inner value’s fields and methods directly through the wrapper.

§Example

use grafos_collections::durable::Durable;
use grafos_std::block::BlockBuilder;
use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
struct Data { values: Vec<u32> }

let lease = BlockBuilder::new().acquire()?;
let mut d = Durable::new(Data { values: vec![1, 2, 3] }, lease);

// Deref access
assert_eq!(d.values.len(), 3);

// Mutate and checkpoint
d.inner_mut().values.push(4);
d.checkpoint()?;

Implementations§

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impl<T: Serialize + DeserializeOwned> Durable<T>

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pub fn new(inner: T, block_lease: BlockLease) -> Self

Wrap a value with a block lease for checkpointing.

Does not write anything to the block lease. Call checkpoint() to persist the value.

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pub fn inner(&self) -> &T

Returns a reference to the inner value.

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pub fn inner_mut(&mut self) -> &mut T

Returns a mutable reference to the inner value.

This does not increment the mutation counter. Use mutate() if you want auto-checkpoint tracking.

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pub fn set_auto_checkpoint(&mut self, batch_size: Option<u64>)

Enable auto-checkpoint: after every batch_size calls to mutate(), the state is automatically checkpointed to block storage.

Pass 0 or call with None to disable auto-checkpoint.

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pub fn mutate<F>(&mut self, f: F) -> Result<()>
where F: FnOnce(&mut T),

Apply a mutation to the inner value and optionally auto-checkpoint.

The closure f receives &mut T and can modify it. After the closure returns, the mutation counter is incremented. If auto-checkpoint is enabled and the counter reaches the batch size, checkpoint() is called automatically and the counter resets to zero.

§Errors

Returns an error only if auto-checkpoint triggers and the checkpoint itself fails.

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pub fn mutation_count(&self) -> u64

Returns the number of mutations since the last checkpoint (or since auto-checkpoint was enabled).

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pub fn lease_id(&self) -> u128

Returns the lease ID of the block lease for external renewal management (e.g. via [grafos_leasekit::RenewalManager]).

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pub fn expires_at_unix_secs(&self) -> u64

Returns the expiry time (unix seconds) of the block lease for external renewal management.

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pub fn into_block_lease(self) -> BlockLease

Consume the Durable and return the block lease.

Useful for passing the same lease to restore() after a checkpoint, simulating a process restart that re-opens the same block device.

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pub fn checkpoint(&self) -> Result<()>

Serialize the inner value and write it to block storage.

Writes a header to block 0 (magic, version, data length) followed by the postcard-serialized data across blocks 1..N.

§Errors

FabricError::CapacityExceeded if the serialized data requires more blocks than available on the device.
FabricError::IoError if serialization or block write fails.

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