nibrunnerHost capacity
How many apps a host is laid out for, what this machine holds, and how to change it.
max_apps is the first key in config.toml, above every section:
max_apps = 300Everything that counts slots follows from it: the slot ring, the eight loopback ports each slot
reserves from 21000, the nbd minors on a zerofs host, the 1024 entries an app is given in the
kernel's connection-tracking table, and what the metrics page calls nibrunner_slots{of="total"}.
A host that is full says so by naming this key.
What this machine holds
install measures three bounds, assuming an app to be 1 vCPU, 256 MiB and an 8 GiB volume:
| Bound | What it is |
|---|---|
| Runs at once | Guest memory, after the host and the storage cache, over 256 MiB. |
| Holds on disk | The disk under paths.snapshot_dir, after the storage cache and an 8 GiB reserve, over one snapshot — plus one volume on a local-file host. |
| Fits on its ports | 5567: each slot reserves eight ports from 21000, and the last port has to be a port. |
A host whose configuration install wrote gets the least of the three, with the line above the
key naming all of them. Every nibrunnerd start then says the three against the number set:
max_apps = 300: assuming an app is 1 vCPU, 256 MiB and 8 GiB to start, this host runs 29 at once, holds 320 on disk, and fits 5567 on its ports; above 29 counts on apps sleepingAbove what the memory runs at once is only said — that is what sleeping
is for. Above what the disk holds or the ports fit, start says the number to set instead. Both
are advice, not refusals: an app given more counts for more, and the number is yours to keep.
Changing it
- Edit
max_apps. - Run
nibrunnerd start.
Good to know
- Raising it on a
zerofshost asks for a reboot. The nbd module is loaded withmax_apps + 1minors, which cannot be raised in place, andstartsays so rather than reloading a module with volumes attached to it. - Lowering it below a slot an app holds moves that app to a new slot on the next start: a new loopback port and a new guest address.