Persist most recent safe block

[mattsse]

Describe the feature

same as

reth/crates/storage/db/src/tables/mod.rs

Lines 417 to 418 in d027b7b

	/// Last finalized block key
	LastFinalizedBlock,

but for the safe block

TODO

• add variant
• extend and rename trait:

reth/crates/storage/provider/src/traits/finalized_block.rs

Lines 4 to 16 in d027b7b

	/// Functionality to read the last known finalized block from the database.
	pub trait FinalizedBlockReader: Send + Sync {
	/// Returns the last finalized block number.
	///
	/// If no finalized block has been written yet, this returns `None`.
	fn last_finalized_block_number(&self) -> ProviderResult<Option<BlockNumber>>;
	}
	/// Functionality to write the last known finalized block to the database.
	pub trait FinalizedBlockWriter: Send + Sync {
	/// Saves the given finalized block number in the DB.
	fn save_finalized_block_number(&self, block_number: BlockNumber) -> ProviderResult<()>;
	}

store safe block same as

reth/crates/engine/tree/src/tree/mod.rs

Lines 2375 to 2382 in d027b7b

	if Some(finalized.num_hash()) !=
	self.canonical_in_memory_state.get_finalized_num_hash()
	{
	// we're also persisting the finalized block on disk so we can reload it on
	// restart this is required by optimism which queries the finalized block: <https://github.com/ethereum-optimism/optimism/blob/c383eb880f307caa3ca41010ec10f30f08396b2e/op-node/rollup/sync/start.go#L65-L65>
	let _ = self.persistence.save_finalized_block_number(finalized.number);
	self.canonical_in_memory_state.set_finalized(finalized);
	}

but for

reth/crates/engine/tree/src/tree/mod.rs

Lines 2404 to 2406 in d027b7b

	Ok(Some(finalized)) => {
	self.canonical_in_memory_state.set_safe(finalized);
	}

Additional context

No response

[Benjtalkshow]

@mattsse
Can I be assigned to this issue? I will tackle it as soon as possible. Thanks

[0xdevcollins]

Can I be assigned this issue?

[mattsse]

this was more urgent, so I took it, ty