UpSlim

Minimal uptime monitoring server written in Rust.
Checks HTTP endpoints and TCP services. Alerts on Slack. Runs anywhere.

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What it does

UpSlim runs as a single process, reads a YAML config, and periodically checks your services. When something goes down it alerts you on Slack. When it recovers, it tells you that too.

• HTTP monitors — checks status codes, response times, and JSON body fields
• TCP monitors — verifies that a port is reachable within a timeout
• Smart alerting — configurable failure/success thresholds to avoid flapping noise
• Reminder intervals — re-alerts every N hours while a service stays down
• State persistence — survives restarts without duplicate alerts

Performance

Benchmarked against the production Docker image (scratch-based) on Apple M4 Pro (arm64). Each scenario ran HTTP monitors at 5-second intervals against a local mock server.

Scenario	Monitors	CPU avg	CPU peak	RAM avg	RAM peak
idle	1	0.02%	0.11%	1.2 MB	1.4 MB
light	10	0.19%	0.64%	1.6 MB	2.1 MB
medium	50	0.34%	0.63%	2.3 MB	3.1 MB
heavy	100	0.32%	0.65%	2.4 MB	3.5 MB

Docker image: 1.9 MB. RAM is measured via docker stats. CPU is sampled every 2 seconds. Scaling from 50 → 100 monitors adds ~0.1 MB of RAM — Tokio async tasks are nearly free.

Run pnpm bench from the repo root to reproduce these results.

Quick start

# config/monitors.yaml
alerting:
  - name: slack-ops
    type: slack
    token: ${SLACK_BOT_TOKEN}
    channel: "#ops-alerts"

monitors:
  - name: api
    type: http
    url: "https://api.example.com/health"
    conditions:
      - "[STATUS] == 200"
      - "[RESPONSE_TIME] < 500"
    alerts:
      - name: slack-ops

  - name: database
    type: tcp
    host: "db.internal"
    port: 5432
    conditions:
      - "[CONNECTED] == true"
    alerts:
      - name: slack-ops

docker run -d \
  -v ./config:/config:ro \
  -v upslim-state:/data \
  -e UPSLIM_STATE_DIR=/data \
  -e SLACK_BOT_TOKEN=xoxb-... \
  abians7/upslim-server:latest

Docker Compose

services:
  upslim:
    image: abians7/upslim-server:latest
    volumes:
      - ./config:/config:ro
      - upslim-state:/data
    environment:
      UPSLIM_STATE_DIR: /data
      SLACK_BOT_TOKEN: ${SLACK_BOT_TOKEN}
      RUST_LOG: info
    restart: unless-stopped

volumes:
  upslim-state:

Configuration

Field	Default	Description
interval	60s	Check frequency
timeout	30s	Max wait per check
failure_threshold	3	Failures before alerting
success_threshold	2	Successes before marking recovered
send_on_resolved	true	Send recovery notification

Supports ${ENV_VAR} substitution in any string value. Load from a single file or a directory — all *.yaml files are merged in lexicographic order.

Conditions

[STATUS] == 200
[RESPONSE_TIME] < 500
[BODY].status == healthy
[CONNECTED] == true

Build from source

git clone https://github.com/AbianS/upslim
cd upslim
cargo build --release -p upslim-server
./target/release/upslim-server --config ./config/

Requires Rust 1.86+.

Documentation

Full docs at abians7.github.io/upslim

License

MIT