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fix(planner): raise WS frame cap above doc cap (fixes sync reconnect loop)

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The Yjs sync WebSocket had MAX_MESSAGE_BYTES = 256 KB (per frame) but
MAX_DOC_BYTES = 5 MB (per session doc). A full-state sync frame carries
the entire doc, so any session doc between 256 KB and 5 MB was allowed to
exist yet could never sync: the client's sync frame tripped the 256 KB
per-frame cap, the server closed it (1008), the client reconnected, resent
the same oversized frame, and looped forever — the UI froze, the connection
flapped Verbunden/Verbinde, and the network tab filled with 101 reconnects.

Real routes hit this fast because the BRouter geometry is stored in the doc:
a 4-waypoint, 77 km cycling route was already 305 KB.

Fix: the per-frame cap must be >= the doc cap (a full-doc sync must fit in
one frame). Set MAX_MESSAGE_BYTES = MAX_DOC_BYTES + 256 KB overhead; the
5 MB doc cap stays the real size/abuse guard. Updated the test that had
codified the inverted ordering.

Verified: planner typecheck + lint clean, yjs-server 9/9, planner suite
183/183.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ullrich Schäfer 2026-07-14 08:58:24 +02:00
parent 696ffb7306
commit e34a06ff5a
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2 changed files with 18 additions and 9 deletions
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9
apps/planner/app/lib/yjs-server.test.ts
View file

@ -52,9 +52,12 @@ describe("countActiveSessions", () => {
});
describe("doc-size caps", () => {
it("MAX_MESSAGE_BYTES + MAX_DOC_BYTES are positive and ordered sanely", () => {
expect(MAX_MESSAGE_BYTES).toBeGreaterThan(0);
expect(MAX_DOC_BYTES).toBeGreaterThan(MAX_MESSAGE_BYTES);
it("the per-frame cap can carry a full-doc sync (message cap >= doc cap)", () => {
expect(MAX_DOC_BYTES).toBeGreaterThan(0);
// A full-state sync frame contains the entire doc, so a per-frame cap
// below the doc cap makes docs between the two sizes unsyncable (reconnect
// loop). The frame cap must be at least the doc cap, plus protocol room.
expect(MAX_MESSAGE_BYTES).toBeGreaterThanOrEqual(MAX_DOC_BYTES);
});
it("docByteSize returns 0 for an unknown session", () => {

18
apps/planner/app/lib/yjs-server.ts
View file

@ -11,13 +11,19 @@ import { plannerActiveSessions, plannerConnectedClients } from "./metrics.server
const messageSync = 0;
const messageAwareness = 1;
// Bound the per-WebSocket-message size and per-session doc size. Both
// guards exist to stop a single connected client from filling memory
// (or the persisted `yjs_state` blob) without limit. Picked generously
// — a multi-day route with hundreds of waypoints is well under 100 KB
// of serialized Yjs state — but small enough to refuse abuse.
export const MAX_MESSAGE_BYTES = 256 * 1024; // 256 KB per WS frame
// Bound the per-session doc size — the real abuse guard, stopping a client
// from filling memory or the persisted `yjs_state` blob without limit. A
// route with hundreds of waypoints is well under this once its BRouter
// geometry is stored in the doc, which is what actually drives the size.
export const MAX_DOC_BYTES = 5 * 1024 * 1024; // 5 MB per session doc
// Per-WebSocket-frame cap. It MUST exceed the doc cap: a full-state sync
// (initial load, or any reconnect) puts the entire doc into a single frame,
// so a frame limit below MAX_DOC_BYTES makes any legal-but-larger-than-the-
// -frame doc permanently unsyncable — the client's sync frame is rejected,
// it reconnects, resends the same frame, and loops forever (observed at the
// old 256 KB cap: a 305 KB / 4-waypoint route froze in a reconnect storm).
// The doc cap remains the size limit; this just leaves room to transmit it.
export const MAX_MESSAGE_BYTES = MAX_DOC_BYTES + 256 * 1024; // doc + protocol overhead
// WebSocket close code for policy-violation responses (1008 is the
// standard RFC 6455 code for "received a message that violates policy").
const POLICY_VIOLATION = 1008;