kolyasya Hunting observer leaks
On the server, Meteor 3 observeChanges / observe return a Promise of a handle. Assigning without await stores a Promise. Promises have no .stop(), so teardown either throws or no-ops and the live query keeps running.
Client MiniMongo observeChanges() still returns a handle. Skip client/ and client-only files.
Canonical Teardown Pattern
Meteor.publish('items.view', function (teamId) {
let stopped = false;
let handle = null;
this.onStop(() => {
stopped = true;
handle?.stop();
});
const cursor = Items.find({ teamId });
cursor.observeChangesAsync({
added: (id, fields) => this.added('items', id, fields),
changed: (id, fields) => this.changed('items', id, fields),
removed: (id) => this.removed('items', id),
}).then((h) => {
handle = h;
if (stopped) handle.stop();
});
this.ready();
});
Hunt
Grep the Meteor app (not client/):
rg -n --glob '!client/**' 'observeChanges|observeChangesAsync|\.observeAsync|\.observe\('
Done when every match has a file:line and a class below. An unscored hit is an incomplete hunt.
Classify every hit
| Class | What you see | Severity |
|---|---|---|
| throw | const h = cursor.observeChanges(...) then h.stop() |
onStop TypeError; handle leaks if unsub during setup |
| silent leak | same, but h.stop?.() |
no throw; observer never stopped |
| teardown race | await observeChangesAsync then onStop(() => h.stop()) |
handle leaks if the sub dies during the await |
| fixed | onStop registered first with a stopped flag; await observeChangesAsync / observeAsync; if (stopped) handle.stop() |
keep |
| client | MiniMongo in client/ or a client-only module |
keep sync observeChanges |
await without the flag is teardown race, not fixed. stop?.() is silent leak, not defensive.
Publication find() cursors stay sync. Only the observer API is async.
Report
For each non-fixed, non-client hit: class, file:line, whether onStop runs before the await.
Fix only when asked. Pattern to copy: Canonical teardown pattern (flag + onStop first + observeChangesAsync + if (stopped) handle.stop()).
Monti APM Cannot read properties of null (reading 'id') / trace has not started yet is the agent crashing in subscription.error when _session is gone. Score the app observer (or the pub that called this.error); do not treat Monti as the leak.