flood dissemination

1 files changed, 65 insertions, 0 deletions

diff --git a/src/swarm/flood.rs b/src/swarm/flood.rs
new file mode 100644
index 0000000..39cb096
--- /dev/null
+++ b/src/swarm/flood.rs
@@ -0,0 +1,65 @@
+//! Flooding (`--dissemination flood`, `swarm::dissemination`): a node pushes every
+//! change it gets, at once, to every neighbour but the one it came from. The broadcast
+//! HyParView's paper pairs its views with, and what PlumTree prunes down to a tree: the
+//! baseline the others are measured against. Every link carries every change about
+//! twice (once each way, where both ends got it before the other's push came), so the
+//! messages grow with the neighbours each member keeps; the latency is that of the
+//! fastest path, with no tree to compute or to repair.
+
+use async_trait::async_trait;
+
+use crate::document::ChangeHash;
+use crate::state::AppState;
+use crate::swarm::dissemination::{Dissemination, pass_on};
+use crate::swarm::topology;
+use crate::swarm::tree::Plan;
+
+pub(crate) struct Flood;
+
+#[async_trait]
+impl Dissemination for Flood {
+    fn name(&self) -> &'static str {
+        "flood"
+    }
+
+    /// Every neighbour gets the writer's changes at once, and is told of them in the slow
+    /// round too (`Plan::alone`): with every neighbour a child, no round would tell
+    /// anyone, and a push lost on a lossy link waited for the next write, or a keepalive.
+    async fn plan(&self, state: &AppState, writer: u64) -> Option<Plan> {
+        let _ = writer;
+        let neighbours = topology::our_neighbours(state);
+        Some(Plan {
+            children: neighbours.clone(),
+            alone: neighbours,
+            uncovered: Vec::new(),
+            covered: Vec::new(),
+        })
+    }
+
+    async fn forward(
+        &self,
+        state: &AppState,
+        writer: u64,
+        from: &str,
+        changes: &[ChangeHash],
+    ) -> Option<Plan> {
+        let plan = self.plan(state, writer).await?;
+        Some(pass_on(state, writer, from, changes, plan).await)
+    }
+
+    /// Counted as the trees' counters count (`/admin/stats`): a push with nothing new as
+    /// a message from another than the parent.
+    async fn note_arrival(
+        &self,
+        state: &AppState,
+        peer: &str,
+        writer: Option<u64>,
+        carried: bool,
+        authors: &[(String, Vec<ChangeHash>)],
+    ) {
+        let _ = peer;
+        if writer.is_some() && carried && authors.is_empty() {
+            state.stats.tree_from_other();
+        }
+    }
+}