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Arpad Müller 552249607d apply clippy fixes for 1.88.0 beta (#12331) 
The 1.88.0 stable release is near (this Thursday). We'd like to fix most
warnings beforehand so that the compiler upgrade doesn't require
approval from too many teams.

This is therefore a preparation PR (like similar PRs before it).

There is a lot of changes for this release, mostly because the
`uninlined_format_args` lint has been added to the `style` lint group.
One can read more about the lint
[here](https://rust-lang.github.io/rust-clippy/master/#/uninlined_format_args).

The PR is the result of `cargo +beta clippy --fix` and `cargo fmt`. One
remaining warning is left for the proxy team.

---------

Co-authored-by: Conrad Ludgate <conrad@neon.tech>
2025-06-24 10:12:42 +00:00
..
src
apply clippy fixes for 1.88.0 beta (#12331)
2025-06-24 10:12:42 +00:00
Cargo.toml
Update vm_monitor to edition 2024 (#10916)
2025-02-21 20:29:05 +00:00
README.md
vm-monitor: Switch from memory.high to polling memory.stat (#5524)
2023-10-17 15:30:40 -07:00

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 polls the neon-postgres cgroup's memory usage and sends rolling aggregates to the runner.
  • 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