Symon

Lightweight system metrics exporter for OpenTelemetry

Symon is a dedicated daemon for collecting and exporting system metrics to OpenTelemetry collectors. Unlike traditional monitoring tools with TUI interfaces, Symon is purpose-built for headless operation, making it ideal for server environments.

Features

• 🚀 Lightweight & Fast - Minimal resource footprint, optimized for server environments
• 📊 Comprehensive Metrics - CPU, memory, network, disk, processes, and temperature
• 🔍 Smart Process Filtering - Whitelist/blacklist with regex pattern support
• 📁 External Config Files - Server-specific process lists via include files
• 🔄 OTLP Native - Direct export to OpenTelemetry Collector via gRPC
• ⚙️ Zero UI Overhead - No terminal rendering, just pure metrics collection

Metrics Exported

• CPU: Usage per core
• Memory: RAM and swap usage/total
• Network: RX/TX bytes per interface
• Disk: Usage and total space per mount
• Processes: Top 10 by CPU/Memory (with optional filtering)
• Temperature: System sensors (when available)

All metrics follow OpenTelemetry semantic conventions with proper labels and descriptions.

Installation

From Source

git clone https://github.com/battilo/symon.git
cd symon
cargo build --release
sudo cp target/release/symon /usr/local/bin/

Binary Release

Download the latest release from GitHub Releases.

Quick Start

1. Create a configuration file (symon.toml):

collection_interval_secs = 5

[otlp]
endpoint = "http://localhost:4317"
export_interval_secs = 10
service_name = "symon"

[metrics]
cpu = true
memory = true
network = true
disk = true
processes = true
temperature = true

2. Run Symon:

symon --config symon.toml

3. View metrics in your observability stack (Prometheus + Grafana)

Configuration

Basic Configuration

# How often to collect metrics (seconds)
collection_interval_secs = 5

[otlp]
# OpenTelemetry Collector endpoint
endpoint = "http://localhost:4317"

# How often to export metrics (seconds)
export_interval_secs = 10

# Service identification
service_name = "symon"
service_version = "0.1.0"

# Custom resource attributes
[otlp.resource_attributes]
environment = "production"
datacenter = "us-east-1"
host = "server-01"

Metrics Selection

[metrics]
cpu = true          # CPU usage per core
memory = true       # RAM and swap
network = true      # Network interfaces
disk = true         # Disk usage
processes = true    # Top 10 processes
temperature = true  # System temperatures

Process Filtering

Monitor only specific processes to reduce cardinality:

Option 1: Inline Configuration

[metrics.process_filter]
filter_mode = "whitelist"  # or "blacklist"

# Substring match (case-insensitive)
names = ["nginx", "postgres", "redis"]

# Regex patterns (case-sensitive)
patterns = [
    "^node-v[0-9]+",           # Node.js with version
    "java.*MyApplication",      # Java with specific class
    "^gunicorn: worker \\[.*\\]" # Gunicorn workers
]

# Specific PIDs
pids = [1234, 5678]

Option 2: External File (recommended for multiple servers)

[metrics.process_filter]
include = "processes.toml"  # or "/etc/symon/processes.toml"

processes.toml:

filter_mode = "whitelist"
names = ["nginx", "postgres"]
patterns = ["^docker-.*"]

This allows different process lists per server while keeping the main config identical.

Docker Compose Testing Stack

A complete observability stack is provided for testing:

cd docker-compose
docker-compose up -d

This starts:

• OTEL Collector (ports 4317/4318)
• Prometheus (port 9090)
• Grafana (port 3000, admin/admin)

Then run Symon:

symon -c docker-compose/symon-config-example.toml

Access Grafana at http://localhost:3000 to view the pre-configured "System Overview" dashboard.

Systemd Service

Create /etc/systemd/system/symon.service:

[Unit]
Description=Symon - System Metrics Exporter
After=network.target

[Service]
Type=simple
User=symon
ExecStart=/usr/local/bin/symon --config /etc/symon/symon.toml
Restart=on-failure
RestartSec=5s

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable symon
sudo systemctl start symon
sudo systemctl status symon

Comparison with Bottom

Symon was originally developed as an OpenTelemetry export feature for bottom, but was split into a separate project as it better serves as a dedicated metrics daemon rather than a TUI tool extension.

Feature	Bottom	Symon
Purpose	Interactive TUI monitor	Headless metrics exporter
UI	Rich terminal interface	None (daemon only)
Resource Usage	Higher (rendering)	Minimal (no UI)
OTEL Export	Optional feature	Core purpose
Process Filtering	UI-based	Config-based with regex
Use Case	Developer workstations	Production servers

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option.

Acknowledgments

• Inspired by bottom by Clement Tsang
• Built with OpenTelemetry and sysinfo