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gossipsub: gate flood-publish by message size — fix drive saturation + outbox overflow (coverage ceiling) #279

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Merged
ch4r10t33r merged 1 commit into from
Jun 28, 2026
Merged

gossipsub: gate flood-publish by message size — fix drive saturation + outbox overflow (coverage ceiling) #279

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11 changes: 10 additions & 1 deletion src/protocols/gossipsub/runtime.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,15 @@ pub const GossipsubConfig = struct {
/// message delivers it to ALL subscribed peers (remote_interest), not just
/// the current mesh — decouples first-hop coverage from mesh convergence.
flood_publish: bool = true,
/// Only flood-publish messages at/below this encoded wire size; larger ones
/// (e.g. ~3 MiB blocks) fall back to mesh-forward. flood_publish on a DENSE
/// topic (block: ~31 subscribers) multiplies the originator's outbound by the
/// subscriber count — for large messages that saturates the single drive loop
/// and overflows the bulk outbox (dropping frames), for ZERO coverage benefit:
/// coverage is about small attestations, and blocks propagate fine via the
/// mesh. So flood only the small (attestation/aggregation) messages where it
/// fixes first-hop coverage. Tunable.
flood_publish_max_message_bytes: usize = 128 * 1024,
/// Extra heartbeats a pruned peer stays GRAFT-ineligible past exact backoff
/// expiry (rust-libp2p backoff_slack). Prevents lockstep re-GRAFT flap. 0 =
/// exact (no slack).
Expand Down Expand Up @@ -1565,7 +1574,7 @@ pub const Gossipsub = struct {
if (self.subs.contains(topic)) {
try self.ensureTopicMesh(topic);
const mp = self.mesh.getPtr(topic).?;
const ri: ?*TopicMesh = if (self.cfg.flood_publish) self.remote_interest.getPtr(topic) else null;
const ri: ?*TopicMesh = if (self.cfg.flood_publish and inner.len <= self.cfg.flood_publish_max_message_bytes) self.remote_interest.getPtr(topic) else null;
if (ri) |rip| {
// rust-libp2p flood_publish (default on): the ORIGINATOR delivers
// its own message to EVERY subscribed peer, not just the current
Expand Down
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