Caps the number of active sessions (routes users have added) on your node. A user who picks your node when it is full is told it has reached its limit; a user who picks the country gets another node.
Values
- 0: the platform default, 500.
- 1–10000: your own cap. Set a lower one on a small server rather than relying on 500.
The overload check
The platform stops sending new users to a node as soon as the people on it fill the cap. Whatever the cap, it also stops when 3 of its last 5 heartbeats show any of these:
- memory above 90%;
- a load average above twice its CPU cores, over the last 15 minutes;
- the kernel's connection table 80% full;
- connections dropped for want of room since the heartbeat before: any by a full connection table, or 10 or more new ones by a full listen queue (connections the server did not accept in time);
- bandwidth above 80% of the link speed, when it is known.
The number of connections a node holds counts for nothing by itself: an exit holds several for each connection of a user. Nor do the connections the kernel turns away for other reasons, which every server on the internet sees: a clash of two first packets, a half-open connection from an address that does not answer. The connection table is reported by agent 0.4.20 and newer, the drops by 0.4.23 and newer; an older agent is judged by the rest.
olcRTC has its own, separate limit on how many users one origin takes at a time.
The dashboard shows each node's occupancy as a bar, sessions out of the cap. Users see the same load figure on the marketplace.