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// Copyright (c) Aptos
// SPDX-License-Identifier: Apache-2.0
use crate::{proof_fetcher::ProofFetcher, DbReader};
use anyhow::{format_err, Result};
use aptos_crypto::{hash::CryptoHash, HashValue};
use aptos_state_view::{StateView, StateViewId};
use aptos_types::{
proof::SparseMerkleProof,
state_store::{state_key::StateKey, state_value::StateValue},
transaction::Version,
write_set::WriteSet,
};
use parking_lot::RwLock;
use scratchpad::{FrozenSparseMerkleTree, SparseMerkleTree, StateStoreStatus};
use std::collections::{HashMap, HashSet};
/// `CachedStateView` is like a snapshot of the global state comprised of state view at two
/// levels, persistent storage and memory.
pub struct CachedStateView<T> {
/// For logging and debugging purpose, identifies what this view is for.
id: StateViewId,
/// A readable snapshot in the persistent storage.
snapshot: Option<(Version, HashValue)>,
/// The in-memory state on top of the snapshot.
speculative_state: FrozenSparseMerkleTree<StateValue>,
/// The cache of verified account states from `reader` and `speculative_state_view`,
/// represented by a hashmap with an account address as key and a pair of an ordered
/// account state map and an an optional account state proof as value. When the VM queries an
/// `access_path`, this cache will first check whether `reader_cache` is hit. If hit, it
/// will return the corresponding value of that `access_path`; otherwise, the account state
/// will be loaded into the cache from scratchpad or persistent storage in order as a
/// deserialized ordered map and then be returned. If the VM queries this account again,
/// the cached data can be read directly without bothering storage layer. The proofs in
/// cache are needed by ScratchPad after VM execution to construct an in-memory sparse Merkle
/// tree.
/// ```text
/// +----------------------------+
/// | In-memory SparseMerkleTree <------+
/// +-------------^--------------+ |
/// | |
/// write sets |
/// | cached account state map
/// +-------+-------+ proof
/// | V M | |
/// +-------^-------+ |
/// | |
/// value of `account_address/path` |
/// | |
/// +---------------------------+---------------------+-------+
/// | +-------------------------+---------------------+-----+ |
/// | | state_cache, state_key_to_proof_cache | |
/// | +---------------^---------------------------^---------+ |
/// | | | |
/// | state store values only state blob proof |
/// | | | |
/// | | | |
/// | +---------------+--------------+ +----------+---------+ |
/// | | speculative_state | | reader | |
/// | +------------------------------+ +--------------------+ |
/// +---------------------------------------------------------+
/// ```
/// Cache of state key to state value, which is used in case of fine grained storage object.
/// Eventually this should replace the `account_to_state_cache` as we deprecate account state blob
/// completely and migrate to fine grained storage. A value of None in this cache reflects that
/// the corresponding key has been deleted. This is a temporary hack until we support deletion
/// in JMT node.
state_cache: RwLock<HashMap<StateKey, StateValue>>,
proof_fetcher: T,
}
impl<T> CachedStateView<T>
where
T: ProofFetcher,
{
/// Constructs a [`CachedStateView`] with persistent state view in the DB and the in-memory
/// speculative state represented by `speculative_state`. The persistent state view is the
/// latest one preceding `next_version`
pub fn new(
id: StateViewId,
reader: &dyn DbReader,
next_version: Version,
speculative_state: SparseMerkleTree<StateValue>,
proof_fetcher: T,
) -> Result<Self> {
// n.b. Freeze the state before getting the state snapshot, otherwise it's possible that
// after we got the snapshot, in-mem trees newer than it gets dropped before being frozen,
// due to a commit happening from another thread.
let speculative_state = speculative_state.freeze();
let snapshot = reader.get_state_snapshot_before(next_version)?;
Ok(Self {
id,
snapshot,
speculative_state,
state_cache: RwLock::new(HashMap::new()),
proof_fetcher,
})
}
pub fn prime_cache_by_write_set(&self, write_sets: &[WriteSet]) -> Result<()> {
write_sets
.iter()
.flat_map(|write_set| write_set.iter())
.map(|(key, _)| key)
.collect::<HashSet<_>>()
.into_iter()
.try_for_each(|key| self.get_state_value(key).map(|_| ()))
}
pub fn into_state_cache(self) -> StateCache {
StateCache {
frozen_base: self.speculative_state,
state_cache: self.state_cache.into_inner(),
proofs: self.proof_fetcher.get_proof_cache(),
}
}
fn get_state_value_internal(&self, state_key: &StateKey) -> Result<Option<StateValue>> {
// Do most of the work outside the write lock.
let key_hash = state_key.hash();
let state_value_option = match self.speculative_state.get(key_hash) {
StateStoreStatus::ExistsInScratchPad(value) => Some(value),
StateStoreStatus::DoesNotExist => None,
// No matter it is in db or unknown, we have to query from db since even the
// former case, we don't have the blob data but only its hash.
StateStoreStatus::ExistsInDB | StateStoreStatus::Unknown => {
match self.snapshot {
Some((version, root_hash)) => {
let (value, proof) = self
.proof_fetcher
.fetch_state_value_and_proof(state_key, version)?;
// TODO: proof verification can be opted out, for performance
if let Some(proof) = proof {
proof
.verify(root_hash, key_hash, value.as_ref())
.map_err(|err| {
format_err!(
"Proof is invalid for key {:?} with state root hash {:?}: {}",
state_key,
root_hash,
err
)
})?;
}
value
}
None => None,
}
}
};
Ok(state_value_option)
}
}
pub struct StateCache {
pub frozen_base: FrozenSparseMerkleTree<StateValue>,
pub state_cache: HashMap<StateKey, StateValue>,
pub proofs: HashMap<HashValue, SparseMerkleProof>,
}
impl<T> StateView for CachedStateView<T>
where
T: ProofFetcher,
{
fn id(&self) -> StateViewId {
self.id
}
fn get_state_value(&self, state_key: &StateKey) -> Result<Option<Vec<u8>>> {
// First check if the cache has the state value.
if let Some(contents) = self.state_cache.read().get(state_key) {
// This can return None, which means the value has been deleted from the DB.
return Ok(contents.maybe_bytes.as_ref().cloned());
}
let state_value_option = self.get_state_value_internal(state_key)?;
// Update the cache if still empty
let mut cache = self.state_cache.write();
let new_value = cache
.entry(state_key.clone())
.or_insert_with(|| state_value_option.unwrap_or_default());
Ok(new_value.maybe_bytes.as_ref().cloned())
}
fn is_genesis(&self) -> bool {
self.snapshot.is_none()
}
}