Node lookups spike memory and the spike persists on JS-heavy pages (linkedin.com/in/<account>, behind login)

[dashn9]

Repeated node lookups against a logged-in linkedin.com/in/<account> push memory up sharply, and it does not come back down between lookups. Ordinary pages are fine; it shows on DOM-heavy, script-heavy ones.

Two things in the CDP lookup path look like they contribute.

1. DOM.getDocument on every locate

locate resolves the document root before every query:

https://github.com/dashn9/rustenium/blob/main/rustenium/src/conduit/cdp/adapter.rs#L316

let root_id = self.get_root_node_id().await?;
let cmd = QuerySelector::builder().node_id(root_id)...

Each DOM.getDocument makes Chrome's DOM agent mint and retain a fresh NodeId → backend-node mapping. That map is owned by the browser and is only dropped on document update or DOM.disable, so it grows per call and the growth is browser-side — which matches the spike persisting rather than being reclaimed when the DomNode goes out of scope on our side. locate_all and wait_for (which polls locate every 100ms) multiply it.

2. DescribeNode with depth(-1)

describe_by_id asks for the whole subtree:

https://github.com/dashn9/rustenium/blob/main/rustenium/src/conduit/cdp/adapter.rs#L305

DescribeNode::builder().node_id(node_id).depth(-1).build()

So matching a container selector on a LinkedIn profile serialises and deserialises that entire subtree into a DomNode tree, every time. Most callers want the node itself — its box, its attributes, its text — not its descendants.

Repro

1. Open a logged-in linkedin.com/in/<account>.
2. Loop locate on a container selector (or any wait_for, which polls it) a few hundred times.
3. Watch RSS of the browser process and of the driving process. Both climb; neither returns to the baseline after the loop ends.

Suggested direction

• Cache the document root per navigation instead of calling DOM.getDocument per lookup, and invalidate it on Page.frameNavigated / DOM.documentUpdated.
• Take the depth as an option rather than hardcoding -1, defaulting to the node alone. A caller that wants a subtree can ask; today everyone pays for one.