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//! # Database Cache
//! This is an in-memory cache that is used to store the state of the DHT database.
use crate::dht_op::DhtOpType;
use crate::share::RwShare;
use error::*;
use holo_hash::*;
use holochain_sqlite::prelude::*;
use rusqlite::named_params;
use std::collections::HashMap;
use std::ops::RangeInclusive;
use std::sync::Arc;
#[cfg(test)]
mod tests;
#[allow(missing_docs)]
pub mod error;
#[derive(Clone)]
/// This cache allows us to track selected database queries that
/// are too slow to run frequently.
/// The queries are lazily evaluated and cached.
/// Then the cache is updated in memory without needing to
/// go to the database.
pub struct DhtDbQueryCache {
/// The database this is caching queries for.
dht_db: DbRead<DbKindDht>,
/// The cache of agent activity queries.
activity: Arc<tokio::sync::OnceCell<ActivityCache>>,
}
type ActivityCache = RwShare<HashMap<Arc<AgentPubKey>, ActivityState>>;
#[derive(Default, Debug, Clone, PartialEq, Eq)]
/// The state of an authors activity according to this authority.
pub struct ActivityState {
/// The bounds of integrated and ready to integrate activity.
pub bounds: ActivityBounds,
/// Any activity that is ready to be integrated but is waiting
/// for one or more upstream chain items to be marked ready before it can
/// be integrated.
/// This is an ordered sparse set.
pub awaiting_deps: Vec<u32>,
}
#[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
/// The state of an agent's activity.
pub struct ActivityBounds {
/// The highest agent activity header sequence that is already integrated.
pub integrated: Option<u32>,
/// The highest consecutive header sequence number that is ready to integrate.
pub ready_to_integrate: Option<u32>,
}
impl std::ops::Deref for ActivityState {
type Target = ActivityBounds;
fn deref(&self) -> &Self::Target {
&self.bounds
}
}
#[cfg(any(test, feature = "test_utils"))]
impl DhtDbQueryCache {
/// Get the caches internal state for testing.
pub async fn get_state(&self) -> &ActivityCache {
self.get_or_try_init().await.unwrap()
}
}
impl DhtDbQueryCache {
/// Create a new cache for dht database queries.
pub fn new(dht_db: DbRead<DbKindDht>) -> Self {
Self {
dht_db,
activity: Default::default(),
}
}
/// Lazily initiate the activity cache.
async fn get_or_try_init(&self) -> DatabaseResult<&ActivityCache> {
self.activity
.get_or_try_init(|| {
let db = self.dht_db.clone();
async move {
let (activity_integrated, mut all_activity) = db
.async_reader(|txn| {
// Get the highest integrated sequence number for each agent.
let activity_integrated: Vec<(AgentPubKey, u32)> = txn
.prepare_cached(
holochain_sqlite::sql::sql_cell::ACTIVITY_INTEGRATED_UPPER_BOUND,
)?
.query_map(
named_params! {
":register_activity": DhtOpType::RegisterAgentActivity,
},
|row| {
Ok((
row.get::<_, Option<AgentPubKey>>(0)?,
row.get::<_, Option<u32>>(1)?,
))
},
)?
.filter_map(|r| match r {
Ok((a, seq)) => Some(Ok((a?, seq?))),
Err(e) => Some(Err(e)),
})
.collect::<rusqlite::Result<Vec<_>>>()?;
// Get all the agents that have activity ready to be integrated.
let all_activity_agents: Vec<Arc<AgentPubKey>> = txn
.prepare_cached(
holochain_sqlite::sql::sql_cell::ALL_ACTIVITY_AUTHORS,
)?
.query_map(
named_params! {
":register_activity": DhtOpType::RegisterAgentActivity,
},
|row| Ok(Arc::new(row.get::<_, AgentPubKey>(0)?)),
)?
.collect::<rusqlite::Result<Vec<_>>>()?;
// Any agent activity that is currently ready to be integrated.
let mut any_ready_activity: HashMap<Arc<AgentPubKey>, ActivityState> =
HashMap::with_capacity(all_activity_agents.len());
let mut stmt = txn.prepare_cached(
holochain_sqlite::sql::sql_cell::ALL_READY_ACTIVITY,
)?;
// For each agent with activity that is ready to be integrated gather all
// the chain items and add them to the `awaiting_deps` list.
for author in all_activity_agents {
let awaiting_deps = stmt
.query_map(
named_params! {
":register_activity": DhtOpType::RegisterAgentActivity,
":author": author,
},
|row| row.get::<_, u32>(0),
)?
.collect::<rusqlite::Result<Vec<_>>>()?;
let state = ActivityState {
awaiting_deps,
..Default::default()
};
any_ready_activity.insert(author, state);
}
DatabaseResult::Ok((activity_integrated, any_ready_activity))
})
.await?;
// Update the activity with the integrated sequence numbers.
for (agent, i) in activity_integrated {
let state = all_activity.entry(Arc::new(agent)).or_default();
state.bounds.integrated = Some(i);
}
// Now for each agent we update their activity so that any chain items
// that are ready to integrate are moved out of the `awaiting_deps` list.
for state in all_activity.values_mut() {
update_ready_to_integrate(state, None);
}
Ok(RwShare::new(all_activity))
}
})
.await
}
/// Get any activity that is ready to be integrated.
/// This returns a range of activity that is ready to be integrated
/// for each agent.
pub async fn get_activity_to_integrate(
&self,
) -> DatabaseResult<Vec<(Arc<AgentPubKey>, RangeInclusive<u32>)>> {
Ok(self.get_or_try_init().await?.share_ref(|activity| {
activity
.iter()
.filter_map(|(agent, ActivityState { bounds, .. })| {
// If there is anything ready to integrated then it will be the end of the range.
let ready_to_integrate = bounds.ready_to_integrate?;
// The start of the range will be one more then the last integrated item or
// if there is nothing integrated then the start will be also the ready_to_integrate.
// This is why we use an inclusive range.
let start = bounds
.integrated
.and_then(|i| i.checked_add(1))
.filter(|i_prime| *i_prime <= ready_to_integrate)
.unwrap_or(ready_to_integrate);
Some((agent.clone(), start..=ready_to_integrate))
})
.collect()
}))
}
/// Is the SourceChain empty for this [`AgentPubKey`]?
pub async fn is_chain_empty(&self, author: &AgentPubKey) -> DatabaseResult<bool> {
Ok(self.get_or_try_init().await?.share_ref(|activity| {
activity
.get(author)
.map_or(true, |state| state.bounds.integrated.is_none())
}))
}
/// Mark agent activity as actually integrated.
pub async fn set_all_activity_to_integrated(
&self,
integrated_activity: Vec<(Arc<AgentPubKey>, RangeInclusive<u32>)>,
) -> DbCacheResult<()> {
self.get_or_try_init().await?.share_mut(|activity| {
let mut new_bounds = ActivityBounds::default();
// For each authors activity run the activity check then update the activity state.
for (author, seq_range) in integrated_activity {
let prev_bounds = activity.get_mut(author.as_ref());
// Set the new bounds to the start of this range for the check.
new_bounds.integrated = Some(*seq_range.start());
// Check that it makes sense to integrate the first activity in this range.
if !update_activity_check(prev_bounds.as_deref().map(|p| &p.bounds), &new_bounds) {
return Err(DbCacheError::ActivityOutOfOrder(
prev_bounds.and_then(|p| p.integrated).unwrap_or(0),
new_bounds.integrated.unwrap_or(0),
));
}
// Because ranges are sequential we know by induction that the last activity makes sense to add.
// Update the bounds to the end of this range.
new_bounds.integrated = Some(*seq_range.end());
// If there is previous bounds then update the bounds.
match prev_bounds {
Some(prev_bounds) => update_activity_inner(prev_bounds, &new_bounds),
None => {
// Otherwise insert the new state.
activity.insert(
author,
ActivityState {
bounds: new_bounds,
..Default::default()
},
);
}
}
}
Ok(())
})
}
/// Set activity to ready to integrate.
pub async fn set_activity_ready_to_integrate(
&self,
agent: &AgentPubKey,
header_sequence: u32,
) -> DbCacheResult<()> {
self.new_activity_inner(
agent,
ActivityBounds {
ready_to_integrate: Some(header_sequence),
..Default::default()
},
)
.await
}
/// Set activity to to integrated.
pub async fn set_activity_to_integrated(
&self,
agent: &AgentPubKey,
header_sequence: u32,
) -> DbCacheResult<()> {
self.new_activity_inner(
agent,
ActivityBounds {
integrated: Some(header_sequence),
..Default::default()
},
)
.await
}
/// Add an authors activity.
async fn new_activity_inner(
&self,
agent: &AgentPubKey,
new_bounds: ActivityBounds,
) -> DbCacheResult<()> {
self.get_or_try_init()
.await?
.share_mut(|activity| update_activity(activity, agent, &new_bounds))
}
}
/// Check activity bounds can be added.
fn update_activity_check(
prev_bounds: Option<&ActivityBounds>,
new_bounds: &ActivityBounds,
) -> bool {
prev_is_empty_new_is_zero(prev_bounds, new_bounds)
&& integrated_is_consecutive(prev_bounds, new_bounds)
}
/// Prev integrated is empty and new integrated is empty or set to zero
fn prev_is_empty_new_is_zero(
prev_bounds: Option<&ActivityBounds>,
new_bounds: &ActivityBounds,
) -> bool {
prev_bounds.map_or(false, |p| p.integrated.is_some())
|| new_bounds.integrated.map_or(true, |i| i == 0)
}
/// If there's already activity marked integrated
/// then only the same or + 1 sequence number can be integrated.
fn integrated_is_consecutive(
prev_bounds: Option<&ActivityBounds>,
new_bounds: &ActivityBounds,
) -> bool {
prev_bounds
.and_then(|p| p.integrated)
.zip(new_bounds.integrated)
.map_or(true, |(p, n)| {
(p == n) || p.checked_add(1).map(|p1| n == p1).unwrap_or(false)
})
}
/// Updates the activity state of an author with new bounds.
fn update_activity(
activity: &mut HashMap<Arc<AgentPubKey>, ActivityState>,
agent: &AgentPubKey,
new_bounds: &ActivityBounds,
) -> DbCacheResult<()> {
let prev_state = activity.get_mut(agent);
if !update_activity_check(prev_state.as_deref().map(|s| &s.bounds), new_bounds) {
return Err(DbCacheError::ActivityOutOfOrder(
prev_state.and_then(|p| p.integrated).unwrap_or(0),
new_bounds.integrated.unwrap_or(0),
));
}
match prev_state {
Some(prev_bounds) => update_activity_inner(prev_bounds, new_bounds),
None => {
// If the new bounds have `ready_to_integrate` and do not equal zero
// then they are awaiting dependencies.
if new_bounds.ready_to_integrate.map_or(false, |i| i != 0) {
activity.insert(
Arc::new(agent.clone()),
ActivityState {
bounds: ActivityBounds {
integrated: new_bounds.integrated,
..Default::default()
},
awaiting_deps: new_bounds.ready_to_integrate.into_iter().collect(),
},
);
} else {
activity.insert(
Arc::new(agent.clone()),
ActivityState {
bounds: *new_bounds,
..Default::default()
},
);
}
}
}
DbCacheResult::Ok(())
}
fn update_activity_inner(prev_state: &mut ActivityState, new_bounds: &ActivityBounds) {
if new_bounds.integrated.is_some() {
prev_state.bounds.integrated = new_bounds.integrated;
}
update_ready_to_integrate(prev_state, new_bounds.ready_to_integrate);
}
/// Updates the ready to integrate state of an activity.
/// This function is a bit complex but is heavily tested and maintains the
/// chain activity can only be set to ready if it makes sense to.
fn update_ready_to_integrate(prev_state: &mut ActivityState, new_ready: Option<u32>) {
// There is a new chain item that is ready for integration.
if let Some(new_ready) = new_ready {
match prev_state {
// Nothing is integrated or currently ready to integrate but there could
// be other chain items that are awaiting dependencies.
ActivityState {
bounds:
ActivityBounds {
integrated: None,
ready_to_integrate: ready @ None,
},
awaiting_deps,
} => {
// (0) -> Ready(0)
//
// If we have no state and new_ready is zero
// then the new ready_to_integrate is set to zero.
if new_ready == 0 {
*ready = Some(new_ready);
// (x) -> Out(x) where x > 0
//
// If new_ready is not zero then it is added to awaiting_deps.
} else {
awaiting_deps.push(new_ready);
awaiting_deps.sort_unstable();
}
}
// There is existing chain items that are ready to integrate.
ActivityState {
bounds:
ActivityBounds {
integrated: _,
ready_to_integrate: Some(x),
},
awaiting_deps,
} => {
// (Ready(x), x') -> Ready(x')
//
// If ready_to_integrate + 1 == new_ready then we know this
// new ready is consecutive from the previous ready_to_integrate.
if x.checked_add(1)
.map_or(false, |x_prime| x_prime == new_ready)
{
let check_awaiting_deps =
|x_prime_prime| awaiting_deps.first().map(|first| x_prime_prime == *first);
// (Ready(x), Out(x''..=y), x') -> Ready(y)
// (Ready(x), Out(x''..=y, z..), x') -> (Ready(y), Out(z..))
//
// If new_ready fills the gap between ready_to_integrate and the
// first sequence in awaiting_deps then we make the end of the sequence
// the new read_to_integrate.
if x.checked_add(2)
.and_then(check_awaiting_deps)
.unwrap_or(false)
{
if let Some(y) = find_consecutive(awaiting_deps) {
*x = y;
}
} else {
*x = new_ready;
}
} else {
// The new ready chain item is not consecutive from the current
// ready so we add it to awaiting_deps.
awaiting_deps.push(new_ready);
awaiting_deps.sort_unstable();
}
}
// There is an existing chain item that is integrated but
// no currently ready to integrate.
ActivityState {
bounds:
ActivityBounds {
integrated: Some(x),
ready_to_integrate: ready @ None,
},
awaiting_deps,
} => {
// (Integrated(x), x') -> (Integrated(x), Ready(x'))
//
// If the new ready is consecutive from the integrated then we
// can set the new ready_to_integrate to the new ready.
if x.checked_add(1)
.map_or(false, |x_prime| x_prime == new_ready)
{
*ready = Some(new_ready);
// (Integrated(x), a) -> (Integrated(x), Out(y)) where a != 'x
//
// The new ready is not consecutive from the integrated so we add
// it to awaiting_deps.
} else {
awaiting_deps.push(new_ready);
awaiting_deps.sort_unstable();
}
}
}
}
// Now we have updated the ready_to_integrate and awaiting_deps if
// there was a new_ready we can check if there is now a new consecutive
// sequence.
match prev_state {
// Check if there is a consecutive sequence from ready_to_integrate to awaiting_deps.
ActivityState {
bounds:
ActivityBounds {
ready_to_integrate: Some(x),
..
},
awaiting_deps,
} => {
if x.checked_add(1)
.and_then(|x_prime| awaiting_deps.first().map(|first| x_prime == *first))
.unwrap_or(false)
{
if let Some(y) = find_consecutive(awaiting_deps) {
*x = y;
}
}
}
// If there is no ready_to_integrate then
// check if there is a consecutive sequence from integrated to awaiting_deps.
ActivityState {
bounds:
ActivityBounds {
integrated: Some(x),
ready_to_integrate: ready @ None,
},
awaiting_deps,
} => {
if x.checked_add(1)
.and_then(|x_prime| awaiting_deps.first().map(|first| x_prime == *first))
.unwrap_or(false)
{
if let Some(y) = find_consecutive(awaiting_deps) {
*ready = Some(y);
}
}
}
// Check if there is a zero in the awaiting deps.
// This should not happen but is here for robustness.
ActivityState {
bounds:
ActivityBounds {
integrated: None,
ready_to_integrate: ready @ None,
},
awaiting_deps,
} => {
if awaiting_deps.first().map_or(false, |first| *first == 0) {
if let Some(y) = find_consecutive(awaiting_deps) {
*ready = Some(y);
}
}
}
}
// Now the ready_to_integrate and awaiting_deps are updated if
// the integrated is the same as the read_to_integrate then that
// chain item was integrated so there is no longer a ready_to_integrate.
if prev_state
.bounds
.integrated
.and_then(|i| prev_state.ready_to_integrate.map(|r| i == r))
.unwrap_or(false)
{
prev_state.bounds.ready_to_integrate = None;
}
}
// Out(x..y) -> (y)
// Out(x..y, z..)) -> (Out(z..), y)
//
// Take the awaiting dependencies and if there's a sequence from the start
// then remove it and return the end of the sequence.
fn find_consecutive(awaiting_deps: &mut Vec<u32>) -> Option<u32> {
if awaiting_deps.len() == 1 {
awaiting_deps.pop()
} else {
let last_consecutive_pos = awaiting_deps
.iter()
.zip(awaiting_deps.iter().skip(1))
.position(|(n, delta)| {
n.checked_add(1)
.map(|n_prime| n_prime != *delta)
.unwrap_or(true)
});
match last_consecutive_pos {
Some(pos) => {
let r = awaiting_deps.get(pos).copied();
// Drop the consecutive seqs.
drop(awaiting_deps.drain(..=pos));
awaiting_deps.shrink_to_fit();
r
}
None => {
let r = awaiting_deps.pop();
awaiting_deps.clear();
r
}
}
}
}
#[cfg(test)]
impl ActivityState {
fn new() -> Self {
Self::default()
}
fn integrated(mut self, i: u32) -> Self {
self.bounds.integrated = Some(i);
self
}
fn ready(mut self, i: u32) -> Self {
self.bounds.ready_to_integrate = Some(i);
self
}
fn awaiting(mut self, i: Vec<u32>) -> Self {
self.awaiting_deps = i;
self
}
}
impl From<DbRead<DbKindDht>> for DhtDbQueryCache {
fn from(db: DbRead<DbKindDht>) -> Self {
Self::new(db)
}
}
impl From<DbWrite<DbKindDht>> for DhtDbQueryCache {
fn from(db: DbWrite<DbKindDht>) -> Self {
Self::new(db.into())
}
}