455 lines
16 KiB
Rust
455 lines
16 KiB
Rust
//! Non-finalized chain state management as defined by [RFC0005]
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//!
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//! [RFC0005]: https://zebra.zfnd.org/dev/rfcs/0005-state-updates.html
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use std::{collections::BTreeSet, mem, sync::Arc};
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use zebra_chain::{
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block::{self, Block},
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history_tree::HistoryTree,
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orchard,
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parameters::Network,
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sapling, sprout, transparent,
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};
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use crate::{
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request::ContextuallyValidBlock,
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service::{check, finalized_state::ZebraDb},
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FinalizedBlock, PreparedBlock, ValidateContextError,
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};
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mod chain;
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mod queued_blocks;
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#[cfg(test)]
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mod tests;
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pub use queued_blocks::QueuedBlocks;
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pub(crate) use chain::Chain;
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/// The state of the chains in memory, including queued blocks.
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#[derive(Debug, Clone)]
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pub struct NonFinalizedState {
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/// Verified, non-finalized chains, in ascending order.
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///
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/// The best chain is `chain_set.last()` or `chain_set.iter().next_back()`.
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pub chain_set: BTreeSet<Arc<Chain>>,
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/// The configured Zcash network.
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//
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// Note: this field is currently unused, but it's useful for debugging.
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pub network: Network,
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}
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impl NonFinalizedState {
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/// Returns a new non-finalized state for `network`.
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pub fn new(network: Network) -> NonFinalizedState {
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NonFinalizedState {
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chain_set: Default::default(),
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network,
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}
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}
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/// Is the internal state of `self` the same as `other`?
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///
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/// [`Chain`] has a custom [`Eq`] implementation based on proof of work,
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/// which is used to select the best chain. So we can't derive [`Eq`] for [`NonFinalizedState`].
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///
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/// Unlike the custom trait impl, this method returns `true` if the entire internal state
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/// of two non-finalized states is equal.
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///
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/// If the internal states are different, it returns `false`,
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/// even if the chains and blocks are equal.
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#[cfg(test)]
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pub(crate) fn eq_internal_state(&self, other: &NonFinalizedState) -> bool {
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// this method must be updated every time a field is added to NonFinalizedState
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self.chain_set.len() == other.chain_set.len()
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&& self
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.chain_set
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.iter()
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.zip(other.chain_set.iter())
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.all(|(self_chain, other_chain)| self_chain.eq_internal_state(other_chain))
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&& self.network == other.network
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}
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/// Finalize the lowest height block in the non-finalized portion of the best
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/// chain and update all side-chains to match.
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pub fn finalize(&mut self) -> FinalizedBlock {
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// Chain::cmp uses the partial cumulative work, and the hash of the tip block.
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// Neither of these fields has interior mutability.
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// (And when the tip block is dropped for a chain, the chain is also dropped.)
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#[allow(clippy::mutable_key_type)]
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let chains = mem::take(&mut self.chain_set);
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let mut chains = chains.into_iter();
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// extract best chain
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let mut best_chain = chains.next_back().expect("there's at least one chain");
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// clone if required
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let write_best_chain = Arc::make_mut(&mut best_chain);
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// extract the rest into side_chains so they can be mutated
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let side_chains = chains;
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// remove the lowest height block from the best_chain to be finalized
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let finalizing = write_best_chain.pop_root();
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// add best_chain back to `self.chain_set`
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if !best_chain.is_empty() {
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self.chain_set.insert(best_chain);
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}
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// for each remaining chain in side_chains
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for mut chain in side_chains {
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if chain.non_finalized_root_hash() != finalizing.hash {
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// If we popped the root, the chain would be empty or orphaned,
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// so just drop it now.
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drop(chain);
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continue;
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}
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// otherwise, the popped root block is the same as the finalizing block
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// clone if required
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let write_chain = Arc::make_mut(&mut chain);
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// remove the first block from `chain`
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let chain_start = write_chain.pop_root();
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assert_eq!(chain_start.hash, finalizing.hash);
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// add the chain back to `self.chain_set`
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self.chain_set.insert(chain);
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}
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self.update_metrics_for_chains();
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finalizing.into()
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}
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/// Commit block to the non-finalized state, on top of:
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/// - an existing chain's tip, or
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/// - a newly forked chain.
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#[tracing::instrument(level = "debug", skip(self, finalized_state, prepared))]
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pub fn commit_block(
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&mut self,
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prepared: PreparedBlock,
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finalized_state: &ZebraDb,
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) -> Result<(), ValidateContextError> {
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let parent_hash = prepared.block.header.previous_block_hash;
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let (height, hash) = (prepared.height, prepared.hash);
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let parent_chain = self.parent_chain(
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parent_hash,
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finalized_state.sprout_note_commitment_tree(),
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finalized_state.sapling_note_commitment_tree(),
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finalized_state.orchard_note_commitment_tree(),
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finalized_state.history_tree(),
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)?;
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// If the block is invalid, return the error,
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// and drop the cloned parent Arc, or newly created chain fork.
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let modified_chain = self.validate_and_commit(parent_chain, prepared, finalized_state)?;
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// If the block is valid:
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// - add the new chain fork or updated chain to the set of recent chains
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// - remove the parent chain, if it was in the chain set
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// (if it was a newly created fork, it won't be in the chain set)
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self.chain_set.insert(modified_chain);
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self.chain_set
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.retain(|chain| chain.non_finalized_tip_hash() != parent_hash);
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self.update_metrics_for_committed_block(height, hash);
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Ok(())
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}
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/// Commit block to the non-finalized state as a new chain where its parent
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/// is the finalized tip.
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#[tracing::instrument(level = "debug", skip(self, finalized_state, prepared))]
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pub fn commit_new_chain(
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&mut self,
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prepared: PreparedBlock,
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finalized_state: &ZebraDb,
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) -> Result<(), ValidateContextError> {
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let chain = Chain::new(
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self.network,
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finalized_state.sprout_note_commitment_tree(),
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finalized_state.sapling_note_commitment_tree(),
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finalized_state.orchard_note_commitment_tree(),
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finalized_state.history_tree(),
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finalized_state.finalized_value_pool(),
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);
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let (height, hash) = (prepared.height, prepared.hash);
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// If the block is invalid, return the error, and drop the newly created chain fork
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let chain = self.validate_and_commit(Arc::new(chain), prepared, finalized_state)?;
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// If the block is valid, add the new chain fork to the set of recent chains.
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self.chain_set.insert(chain);
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self.update_metrics_for_committed_block(height, hash);
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Ok(())
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}
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/// Contextually validate `prepared` using `finalized_state`.
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/// If validation succeeds, push `prepared` onto `new_chain`.
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///
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/// `new_chain` should start as a clone of the parent chain fork,
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/// or the finalized tip.
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#[tracing::instrument(level = "debug", skip(self, finalized_state, new_chain))]
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fn validate_and_commit(
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&self,
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new_chain: Arc<Chain>,
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prepared: PreparedBlock,
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finalized_state: &ZebraDb,
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) -> Result<Arc<Chain>, ValidateContextError> {
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let spent_utxos = check::utxo::transparent_spend(
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&prepared,
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&new_chain.unspent_utxos(),
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&new_chain.spent_utxos,
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finalized_state,
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)?;
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check::prepared_block_commitment_is_valid_for_chain_history(
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&prepared,
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self.network,
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&new_chain.history_tree,
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)?;
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check::anchors::anchors_refer_to_earlier_treestates(
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finalized_state,
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&new_chain,
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&prepared,
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)?;
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let contextual = ContextuallyValidBlock::with_block_and_spent_utxos(
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prepared.clone(),
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spent_utxos.clone(),
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)
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.map_err(|value_balance_error| {
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ValidateContextError::CalculateBlockChainValueChange {
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value_balance_error,
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height: prepared.height,
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block_hash: prepared.hash,
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transaction_count: prepared.block.transactions.len(),
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spent_utxo_count: spent_utxos.len(),
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}
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})?;
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// We're pretty sure the new block is valid,
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// so clone the inner chain if needed, then add the new block.
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Arc::try_unwrap(new_chain)
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.unwrap_or_else(|shared_chain| (*shared_chain).clone())
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.push(contextual)
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.map(Arc::new)
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}
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/// Returns the length of the non-finalized portion of the current best chain.
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pub fn best_chain_len(&self) -> u32 {
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self.best_chain()
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.expect("only called after inserting a block")
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.blocks
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.len() as u32
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}
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/// Returns `true` if `hash` is contained in the non-finalized portion of any
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/// known chain.
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pub fn any_chain_contains(&self, hash: &block::Hash) -> bool {
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self.chain_set
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.iter()
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.rev()
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.any(|chain| chain.height_by_hash.contains_key(hash))
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}
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/// Removes and returns the first chain satisfying the given predicate.
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///
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/// If multiple chains satisfy the predicate, returns the chain with the highest difficulty.
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/// (Using the tip block hash tie-breaker.)
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fn find_chain<P>(&mut self, mut predicate: P) -> Option<&Arc<Chain>>
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where
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P: FnMut(&Chain) -> bool,
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{
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// Reverse the iteration order, to find highest difficulty chains first.
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self.chain_set.iter().rev().find(|chain| predicate(chain))
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}
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/// Returns the [`transparent::Utxo`] pointed to by the given
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/// [`transparent::OutPoint`] if it is present in any chain.
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pub fn any_utxo(&self, outpoint: &transparent::OutPoint) -> Option<transparent::Utxo> {
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for chain in self.chain_set.iter().rev() {
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if let Some(utxo) = chain.created_utxos.get(outpoint) {
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return Some(utxo.utxo.clone());
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}
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}
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None
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}
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/// Returns the `block` with the given hash in any chain.
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pub fn any_block_by_hash(&self, hash: block::Hash) -> Option<Arc<Block>> {
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for chain in self.chain_set.iter().rev() {
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if let Some(prepared) = chain
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.height_by_hash
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.get(&hash)
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.and_then(|height| chain.blocks.get(height))
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{
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return Some(prepared.block.clone());
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}
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}
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None
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}
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/// Returns the hash for a given `block::Height` if it is present in the best chain.
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pub fn best_hash(&self, height: block::Height) -> Option<block::Hash> {
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self.best_chain()?
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.blocks
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.get(&height)
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.map(|prepared| prepared.hash)
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}
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/// Returns the tip of the best chain.
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pub fn best_tip(&self) -> Option<(block::Height, block::Hash)> {
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let best_chain = self.best_chain()?;
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let height = best_chain.non_finalized_tip_height();
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let hash = best_chain.non_finalized_tip_hash();
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Some((height, hash))
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}
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/// Returns the block at the tip of the best chain.
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#[allow(dead_code)]
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pub fn best_tip_block(&self) -> Option<&ContextuallyValidBlock> {
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let best_chain = self.best_chain()?;
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best_chain.tip_block()
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}
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/// Returns the height of `hash` in the best chain.
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pub fn best_height_by_hash(&self, hash: block::Hash) -> Option<block::Height> {
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let best_chain = self.best_chain()?;
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let height = *best_chain.height_by_hash.get(&hash)?;
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Some(height)
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}
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/// Returns the height of `hash` in any chain.
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pub fn any_height_by_hash(&self, hash: block::Hash) -> Option<block::Height> {
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for chain in self.chain_set.iter().rev() {
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if let Some(height) = chain.height_by_hash.get(&hash) {
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return Some(*height);
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}
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}
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None
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}
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/// Returns `true` if the best chain contains `sprout_nullifier`.
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#[cfg(test)]
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pub fn best_contains_sprout_nullifier(&self, sprout_nullifier: &sprout::Nullifier) -> bool {
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self.best_chain()
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.map(|best_chain| best_chain.sprout_nullifiers.contains(sprout_nullifier))
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.unwrap_or(false)
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}
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/// Returns `true` if the best chain contains `sapling_nullifier`.
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#[cfg(test)]
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pub fn best_contains_sapling_nullifier(&self, sapling_nullifier: &sapling::Nullifier) -> bool {
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self.best_chain()
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.map(|best_chain| best_chain.sapling_nullifiers.contains(sapling_nullifier))
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.unwrap_or(false)
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}
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/// Returns `true` if the best chain contains `orchard_nullifier`.
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#[cfg(test)]
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pub fn best_contains_orchard_nullifier(&self, orchard_nullifier: &orchard::Nullifier) -> bool {
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self.best_chain()
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.map(|best_chain| best_chain.orchard_nullifiers.contains(orchard_nullifier))
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.unwrap_or(false)
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}
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/// Return the non-finalized portion of the current best chain.
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pub(crate) fn best_chain(&self) -> Option<&Arc<Chain>> {
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self.chain_set.iter().next_back()
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}
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/// Return the chain whose tip block hash is `parent_hash`.
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///
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/// The chain can be an existing chain in the non-finalized state or a freshly
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/// created fork, if needed.
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///
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/// The trees must be the trees of the finalized tip.
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/// They are used to recreate the trees if a fork is needed.
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#[allow(clippy::unwrap_in_result)]
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fn parent_chain(
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&mut self,
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parent_hash: block::Hash,
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sprout_note_commitment_tree: sprout::tree::NoteCommitmentTree,
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sapling_note_commitment_tree: sapling::tree::NoteCommitmentTree,
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orchard_note_commitment_tree: orchard::tree::NoteCommitmentTree,
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history_tree: HistoryTree,
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) -> Result<Arc<Chain>, ValidateContextError> {
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match self.find_chain(|chain| chain.non_finalized_tip_hash() == parent_hash) {
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// Clone the existing Arc<Chain> in the non-finalized state
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Some(chain) => Ok(chain.clone()),
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// Create a new fork
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None => {
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// Check the lowest difficulty chains first,
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// because the fork could be closer to their tip.
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let fork_chain = self
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.chain_set
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.iter()
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.find_map(|chain| {
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chain
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.fork(
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parent_hash,
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sprout_note_commitment_tree.clone(),
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sapling_note_commitment_tree.clone(),
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orchard_note_commitment_tree.clone(),
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history_tree.clone(),
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)
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.transpose()
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})
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.expect(
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"commit_block is only called with blocks that are ready to be committed",
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)?;
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Ok(Arc::new(fork_chain))
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}
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}
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}
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/// Update the metrics after `block` is committed
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fn update_metrics_for_committed_block(&self, height: block::Height, hash: block::Hash) {
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metrics::counter!("state.memory.committed.block.count", 1);
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metrics::gauge!("state.memory.committed.block.height", height.0 as f64);
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if self
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.best_chain()
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.unwrap()
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.blocks
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.iter()
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.next_back()
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.unwrap()
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.1
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.hash
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== hash
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{
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metrics::counter!("state.memory.best.committed.block.count", 1);
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metrics::gauge!("state.memory.best.committed.block.height", height.0 as f64);
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}
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self.update_metrics_for_chains();
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}
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/// Update the metrics after `self.chain_set` is modified
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fn update_metrics_for_chains(&self) {
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metrics::gauge!("state.memory.chain.count", self.chain_set.len() as f64);
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metrics::gauge!(
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"state.memory.best.chain.length",
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self.best_chain_len() as f64,
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);
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}
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}
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