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//! The change publisher: after document changes, which store paths they touched
//! (`AppState::change_events`, for the API's streams, the dashboard and remakes), and
//! a nudge to topology when the member list changed, and to the peer worker when the
//! forget records did.
use std::sync::Arc;
use tracing::{info, warn};
use crate::document::changes;
use crate::document::store::{self, ChangeSet, InLists};
use crate::state::AppState;
pub(crate) async fn run_change_publisher(state: AppState) {
let mut changed = state.change_tx.subscribe();
// The replica's heads (sorted, as of its last refresh: every change refreshes them).
let mut last_heads = state.doc.read().await.heads().to_vec();
info!("Starting change publisher");
while changed.changed().await.is_ok() {
let before = last_heads.clone();
let doc = Arc::clone(&state.doc);
let (heads, paths, conflicts) = tokio::task::spawn_blocking(move || {
let replica = doc.blocking_read();
let heads = replica.heads().to_vec();
if heads == before {
return (heads, Vec::new(), Vec::new());
}
// After an epoch switch the previous heads belong to the old document:
// report the root as changed, which every stream is related to.
if !changes::missing(&replica.doc, &before).is_empty() {
return (heads, vec![Vec::new()], Vec::new());
}
let mut paths = Vec::new();
let mut conflicts = Vec::new();
for changed in store::changed(&replica.doc, &before, &heads, InLists::Index) {
if changed.conflict {
conflicts.push(changed.path.clone());
}
paths.push(changed.path);
}
(heads, paths, conflicts)
})
.await
.expect("change publisher task panicked");
if heads == last_heads {
continue;
}
last_heads = heads;
for path in &conflicts {
warn!(path = ?path, "Concurrent writes produced a conflict");
}
if paths
.iter()
.any(|path| crate::swarm::topology::affects_neighbours(path))
{
state.topology_changed.notify_one();
}
if paths
.iter()
.any(|path| crate::swarm::peer::affects_forget_records(path))
{
state
.forget_records_changed
.store(true, std::sync::atomic::Ordering::Release);
state.peers_due.now();
}
// Fails only when nobody is subscribed.
let _ = state.change_events.send(Arc::new(ChangeSet { paths }));
}
}
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