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src/main.rs

@@ -0,0 +1,83 @@
+use axum::{
+  routing::get,
+  Router,
+  response::{
+      IntoResponse,
+      Response,
+  },
+  http::StatusCode,
+};
+
+use std::net::SocketAddr;
+use std::str::FromStr;
+
+#[tokio::main]
+async fn main() {
+  let mut listen = String::from("[::]:9152");
+  let mut args = std::env::args();
+  args.next();
+  loop {
+    let arg = if let Some(arg) = args.next() {
+      arg
+    } else {
+      break
+    };
+
+    match arg.as_str() {
+      "--help" | "-h" => {
+          println!("Prometheus exporter for NixOS systems");
+          println!("Use --listen <addr:port> bind the web service.");
+          println!("Output will be on /metrics endpoint. HTTP 500 if something broke while scraping.");
+          std::process::exit(0);
+      },
+      "--listen" => {
+        listen = args.next().unwrap();
+      },
+      unknown => {
+        println!("unknown option: {}", unknown);
+        std::process::exit(1)
+      }
+    }
+  }
+
+  let app = Router::new().route("/metrics", get(metrics));
+
+  let addr = SocketAddr::from_str(&listen).unwrap();
+  println!("listening on http://{}", addr);
+  axum::Server::bind(&addr)
+    .serve(app.into_make_service())
+    .await
+    .unwrap();
+}
+
+fn get_current_system() -> Result<(String, String), String> {
+  let symlink = match std::fs::read_link("/run/current-system") {
+    Ok(symlink) => symlink,
+    Err(err) => return Err(err.to_string())
+  };
+
+  let (hash, name) = symlink.file_name()
+    .ok_or_else(String::default)?
+    .to_str()
+    .ok_or_else(String::default)?
+    .split_once("-")
+    .ok_or_else(String::default)?;
+
+  Ok((String::from(hash), String::from(name)))
+}
+
+async fn metrics() -> Response {
+  let current_system = get_current_system();
+  let (hash, name) = match current_system {
+    Ok((hash, name)) => (hash, name),
+    Err(err) => {
+      println!("failed: {}", err);
+      return (StatusCode::INTERNAL_SERVER_ERROR, "").into_response()
+    }
+  };
+
+  (
+    StatusCode::OK,
+    format!("nixos_nixos_current_system_hash{{hash=\"{}\"}}\nnixos_current_system_name{{name=\"{}\"}}", hash, name)
+  ).into_response()
+}