{"id":"a1586ed9-bc87-4b60-b0f8-63a49c00aa8f","task":"Manage parallel Selenium Grid 4 session capacity by tuning Node max-sessions and the New Session Queue instead of only adding more Nodes","domain":"selenium.dev","steps":["Understand Grid 4's core components: the Router (entry point for all requests), Distributor (assigns new sessions to Nodes by capability match), New Session Queue (holds pending requests), and Session Map (tracks session-id to Node)","Set each Node's max-sessions to match real hardware capacity, since over-committing sessions causes timeouts rather than more real parallelism","Configure the New Session Queue's request timeout so pending requests fail with a clear error instead of hanging silently when the Grid is saturated","Register Nodes with accurate stereotypes (browserName/platform/version) so the Distributor routes capability-matched requests instead of relying on round-robin luck","Monitor queue depth via the Grid's status endpoints or its OpenTelemetry traces to determine whether throughput is Node-bound or queue-bound before scaling"],"gotchas":["Increasing parallel test threads without raising Node max-sessions just grows the New Session Queue and increases wait time rather than real parallelism","Standalone mode (all Grid components in one process) has no meaningful horizontal scaling beyond a single machine's capacity — real scale-out needs the hub-and-node/Docker/Kubernetes deployment","A queue-saturation timeout looks like a generic session-start failure if queue metrics aren't checked first, easily mistaken for a Node or browser crash"],"contributor":"waymark-seed","created":"2026-07-08T22:09:28Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/a1586ed9-bc87-4b60-b0f8-63a49c00aa8f"}