rust/neon
1
0
Fork 0
mirror of https://github.com/neondatabase/neon.git synced 2026-01-10 15:02:56 +00:00
Code Issues Packages Projects Releases Wiki Activity
Files
5d8597c2f0d19440eb4a5f744b0559263a35487f
neon/libs/vm_monitor
History
Em Sharnoff 722e5260bf vm-monitor: Don't set cgroup memory.max (#5333) 
All it does is make postgres OOM more often (which, tbf, means we're
less likely to have e.g. compute_ctl get OOM-killed, but that tradeoff
isn't worth it).

Internally, this means removing all references to `memory.max` and the
places where we calculate or store the intended value.

As discussed in the sync earlier.

ref:

- https://neondb.slack.com/archives/C03H1K0PGKH/p1694698949252439?thread_ts=1694505575.693449&cid=C03H1K0PGKH
- https://neondb.slack.com/archives/C03H1K0PGKH/p1695049198622759
2023-09-18 17:47:48 +00:00
..
src
vm-monitor: Don't set cgroup memory.max (#5333)
2023-09-18 17:47:48 +00:00
Cargo.toml
compute_ctl: add vm-monitor (#4946)
2023-08-24 15:54:37 -04:00
README.md
monitor/compute_ctl: remove references to the informant (#5115)
2023-08-29 02:59:27 +03:00

README.md

vm-monitor

The vm-monitor (or just monitor) is a core component of the autoscaling system, along with the autoscale-scheduler and the autoscaler-agents. The monitor has two primary roles: 1) notifying agents when immediate upscaling is necessary due to memory conditions and 2) managing Postgres' file cache and a cgroup to carry out upscaling and downscaling decisions.

More on scaling

We scale CPU and memory using NeonVM, our in-house QEMU tool for use with Kubernetes. To control thresholds for receiving memory usage notifications, we start Postgres in the neon-postgres cgroup and set its memory.{max,high}.

Structure

The vm-monitor is loosely comprised of a few systems. These are:

  • the server: this is just a simple axum server that accepts requests and upgrades them to websocket connections. The server only allows one connection at a time. This means that upon receiving a new connection, the server will terminate and old one if it exists.
  • the filecache: a struct that allows communication with the Postgres file cache. On startup, we connect to the filecache and hold on to the connection for the entire monitor lifetime.
  • the cgroup watcher: the CgroupWatcher manages the neon-postgres cgroup by listening for memory.high events and setting its memory.{high,max} values.
  • the runner: the runner marries the filecache and cgroup watcher together, communicating with the agent throught the Dispatcher, and then calling filecache and cgroup watcher functions as needed to upscale and downscale