Skip to main content

Pi Metrics Exporter

View source on GitHub

This guide walks you through building and running the Pi Metrics Exporter reference on Avocado OS. The app cross-compiles a Rust HTTP service that reads device health from /proc and /sys and serves it as Prometheus metrics on port 9100.

Prerequisites​

  • macOS 10.12+ or Linux (Ubuntu 22.04+, Fedora 39+)
  • Docker Desktop installed and running
  • The latest version of the Avocado CLI

For hardware targets, you will also need:

  • Your target device and any required accessories (SD card, USB cable, serial console adapter)
  • See the Support Matrix for your target's requirements

Initialize​

Initialize a new project from the reference:

avocado init --reference pi-metrics-exporter pi-metrics-exporter
cd pi-metrics-exporter

The reference defaults to the raspberrypi4 target. To target another Raspberry Pi, pass --target:

avocado init --reference pi-metrics-exporter --target raspberrypi5 pi-metrics-exporter

Install​

Install the SDK toolchain, extension dependencies, and runtime packages:

avocado install -f

This pulls the SDK container image and installs the Rust cross-compilation toolchain: nativesdk-rust, nativesdk-cargo, packagegroup-rust-cross-canadian-avocado-<target>, and the target libraries libstd-rs and libstd-rs-dev.

Build​

Build the extensions and assemble the runtime image:

avocado build

The build step runs rust-compile.sh inside the SDK container, which:

  1. Discovers the Rust target triple from RUST_TARGET_PATH (e.g., aarch64-avocado-linux-gnu)
  2. Clears SDK-injected RUSTFLAGS to avoid conflicts
  3. Generates .cargo/config.toml with the correct --sysroot and linker flags
  4. Runs cargo build --release --target $RUST_TARGET

Then rust-install.sh copies the cross-compiled binary to /usr/bin/pi_metrics in the extension sysroot.

Deploy​

Insert an SD card and provision it:

avocado provision -r dev --profile sd

Insert the SD card into the Raspberry Pi and apply power. On first boot the extension's service starts automatically.

Verify​

Log in as root with an empty password. The service starts automatically on boot.

Check the service is running:

systemctl status pi-metrics

Then query the exporter from any host on the same network, using the device's IP:

curl http://<device-ip>:9100/healthz
curl http://<device-ip>:9100/metrics

You should see output like:

# HELP pi_cpu_temperature_celsius CPU temperature in degrees Celsius
# TYPE pi_cpu_temperature_celsius gauge
pi_cpu_temperature_celsius 38.9
# HELP pi_memory_total_bytes Total memory in bytes
# TYPE pi_memory_total_bytes gauge
pi_memory_total_bytes 8185634816
# HELP pi_uptime_seconds System uptime in seconds
# TYPE pi_uptime_seconds gauge
pi_uptime_seconds 106.0
# HELP pi_load_average Load average
# TYPE pi_load_average gauge
pi_load_average{interval="1m"} 0.05

Point Prometheus at it​

Add the device as a scrape target in your prometheus.yml:

scrape_configs:
  - job_name: avocado-device
    static_configs:
      - targets: ["<device-ip>:9100"]

Customize​

Edit the Rust source​

Modify pi-metrics/src/main.rs to change the metrics collected or add new ones.

Add Cargo dependencies​

Edit pi-metrics/Cargo.toml. Keep dependencies pure-Rust so they cross-compile without a C toolchain or OpenSSL:

[dependencies]
tiny_http = "0.12"

Rebuild after changes​

avocado build
avocado provision -r dev