Access queue

An access queue (waiting room) keeps your site up during a launch, a ticket sale or a sudden spike: Corvus lets in only as many visitors as your service can handle and queues the rest in order. Waiting visitors see a page with their position, localized in 8 languages, that refreshes by itself.

Set it up

1. Open Access queues and click Add access queue.
2. Set the capacity (see below) and save.
3. Open the proxy host and choose the queue under Access queue. Protected path / protects the whole site; /event only that part.

Settings

Setting	Meaning
Max concurrent visitors	How many visitors can be inside at once
Admission rate	How many new visitors per second are let in (0 = as soon as a slot frees up)
Inactivity expiry	A visitor's slot is released after this long without requests
Turn validity	A visitor whose turn has come must enter within this time
Queue abandonment	Waiting visitors who stop checking in are removed
When the cache DB is down	Let everyone in (fail-open, favours availability) or Block access (fail-closed, protects capacity)
Max queue length	Beyond this, new visitors are asked to come back later (0 = unlimited)
Queue joins per IP	New queue entries one IP may create per minute
Bind admission to the client network	Admission only works from the same network, so it can't be shared. Visitors who change networks queue again

Choosing the capacity

Start with the number of simultaneous users your service handled comfortably in a load test, and watch Active and Waiting on the dashboard during the event.

During the event

• The dashboard and the Access queues page show active and waiting visitors live.
• Emergency release lets everyone straight through, for example when the spike is over. Turn back on restores the queue.
• An alert can notify you when the backlog grows.

APIs and apps

Pages, images and API calls under the protected path all need an admission. A browser gets it automatically (a cookie) while it waits on the queue page. Requests that can't show the waiting page, such as fetch/XHR calls or apps, get 429 Too Many Requests with a Retry-After header and a small JSON body while they wait. They don't count as server errors.

Cross-site clients

The admission cookie is SameSite=Lax. A client on another site (for example a web app on app.example.org calling api.example.com) won't send it and stays queued. Protect only the paths people open in a browser (e.g. / of the web shop) or put the API on a host without a queue.