rust/neon

mirror of https://github.com/neondatabase/neon.git synced 2026-01-04 12:02:55 +00:00

Files

Em Sharnoff cc29def544 vm-monitor: Ignore LFC in postgres cgroup memory threshold (#8668 )

In short: Currently we reserve 75% of memory to the LFC, meaning that if
we scale up to keep postgres using less than 25% of the compute's
memory.

This means that for certain memory-heavy workloads, we end up scaling
much higher than is actually needed — in the worst case, up to 4x,
although in practice it tends not to be quite so bad.

Part of neondatabase/autoscaling#1030.

2024-10-07 21:25:34 +01:00

src

vm-monitor: Ignore LFC in postgres cgroup memory threshold (#8668 )

2024-10-07 21:25:34 +01:00

Cargo.toml

Remove unnecessary dependencies (#9000 )

2024-09-17 17:55:45 +03:00

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}.

See also: neondatabase/autoscaling
See also: neondatabase/vm-monitor, where initial development of the monitor happened. The repository is no longer maintained but the commit history may be useful for debugging.

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