Export booted system and kernel hash as well

Cargo.lock

@@ -450,7 +450,7 @@ dependencies = [
 
 [[package]]
 name = "nixos-exporter"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
  "axum",
  "reqwest",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nixos-exporter"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 
 [dependencies]

flake.nix

@@ -10,7 +10,7 @@
     in {
       nixos-exporter = pkgs.rustPlatform.buildRustPackage rec {
         pname = "nixos-exporter";
-        version = "0.1.0";
+        version = "0.3.0";
 
         src = ./.;
 

src/main.rs

@@ -59,12 +59,12 @@ impl AppState{
 }
 
 fn parse_nix_store_path(path: std::path::PathBuf) -> Result<(String, String), String> {
-    let (hash, name) = path.file_name()
-        .ok_or_else(String::default)?
+    let (hash, name) = path.iter().nth(3)
+        .ok_or_else(|| String::from("Can't read store path name"))?
         .to_str()
-        .ok_or_else(String::default)?
+        .ok_or_else(|| String::from("Failed converting store path name to string"))?
         .split_once("-")
-        .ok_or_else(String::default)?;
+        .ok_or_else(|| String::from("Failed splitting store path name for hash and name"))?;
     return Ok((hash.to_string(), name.to_string()));
 }
 
@@ -143,20 +143,33 @@ async fn main() {
         .unwrap();
 }
 
-fn get_current_system() -> Result<(String, String), String> {
-    let symlink = std::fs::read_link("/run/current-system").map_err(|err| err.to_string())?;
+fn parse_symlink(path: String) -> Result<(String, String), String> {
+    let symlink = std::fs::read_link(path).map_err(|err| err.to_string())?;
 
     let (hash, name) = parse_nix_store_path(symlink)?;
 
     Ok((String::from(hash), String::from(name)))
 }
 
-async fn metrics() -> Result<(StatusCode, impl IntoResponse), (StatusCode, impl IntoResponse)> {
-    let (hash, name) = get_current_system().map_err(|_err| (StatusCode::INTERNAL_SERVER_ERROR, ""))?;
+fn gen_prometheus_metric(path: String, infix: String) -> Result<String, String> {
+    let (hash, name) = parse_symlink(path).map_err(|err| err)?;
 
+    return Ok(format!("nixos_{}_hash{{hash=\"{}\"}} 1\nnixos_{}_name{{name=\"{}\"}} 1\n", infix, hash, infix, name));
+}
+
+async fn metrics() -> Result<(StatusCode, impl IntoResponse), (StatusCode, impl IntoResponse)> {
+    let mut out = String::new();
+    out.push_str(&gen_prometheus_metric(String::from("/run/current-system"), String::from("current_system"))
+        .map_err(|err| (StatusCode::INTERNAL_SERVER_ERROR, err))?);
+    out.push_str(&gen_prometheus_metric(String::from("/run/current-system/kernel"), String::from("current_system_kernel"))
+        .map_err(|err| (StatusCode::INTERNAL_SERVER_ERROR, err))?);
+    out.push_str(&gen_prometheus_metric(String::from("/run/booted-system"), String::from("booted_system"))
+        .map_err(|err| (StatusCode::INTERNAL_SERVER_ERROR, err))?);
+    out.push_str(&gen_prometheus_metric(String::from("/run/booted-system/kernel"), String::from("booted_system_kernel"))
+        .map_err(|err| (StatusCode::INTERNAL_SERVER_ERROR, err))?);
     return Ok((
         StatusCode::OK,
-        format!("nixos_current_system_hash{{hash=\"{}\"}} 1\nnixos_current_system_name{{name=\"{}\"}} 1\n", hash, name)
+        out,
     ));
 }