In 2-process deployments (COLLAB_URL set) the standalone collab process runs
Hocuspocus onStoreDocument, which emits PAGE_UPDATED with a treeUpdate snapshot
on a collaborative rename. But CollabAppModule has no WsModule, so PageWsListener
(the broadcaster) only exists in the API process — the collab-originated tree
update never reached clients, and other users' sidebars/breadcrumbs went stale.
Bridge it over Redis pub/sub with the API process as the single broadcast
authority:
- PageTreeBridgePublisher (registered ONLY in CollabAppModule) listens for
PAGE_UPDATED and, when a treeUpdate snapshot is present, publishes it to the
collab:tree-update channel. Gated exactly like PageWsListener so content-only
saves never publish noise.
- PageTreeBridgeSubscriber (registered in WsModule, API process) subscribes on a
dedicated duplicated connection and re-broadcasts each snapshot through
WsTreeService.broadcastPageUpdated — the same restriction-aware emitTreeEvent
path, so authorization is preserved.
Double-broadcast is prevented by module placement: the publisher lives only in
the standalone collab process's root module, so in single-process mode it is
never loaded and the local PageWsListener stays the sole broadcaster.
The bridge is optional and fail-safe: publish errors, malformed payloads,
broadcast rejections, an unlistened 'error' on the subscriber connection, and a
subscribe() failure at boot are all caught and logged, never crashing or blocking
the process. NOTE: assumes a single API broadcaster; horizontal API scaling would
need a consumer-group/leader-election instead of fan-out pub/sub.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
