Fix systemd socket activation

Cargo.lock

@@ -1010,6 +1010,15 @@ version = "2.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
+[[package]]
+name = "memoffset"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "488016bfae457b036d996092f6cb448677611ce4449e970ceaf42695203f218a"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -1058,6 +1067,7 @@ dependencies = [
  "prettytable",
  "rand",
  "ratatui",
+ "sd-notify",
  "serde",
  "serde_json",
  "sqlx",
@@ -1079,6 +1089,7 @@ dependencies = [
  "cfg-if",
  "cfg_aliases",
  "libc",
+ "memoffset",
 ]
 
 [[package]]
@@ -1524,6 +1535,12 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "sd-notify"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4646d6f919800cd25c50edb49438a1381e2cd4833c027e75e8897981c50b8b5e"
+
 [[package]]
 name = "serde"
 version = "1.0.208"

Cargo.toml

@@ -20,6 +20,7 @@ nix = { version = "0.29.0", features = ["fs", "process", "socket", "user"] }
 prettytable = "0.10.0"
 rand = "0.8.5"
 ratatui = { version = "0.28.0", optional = true }
+sd-notify = "0.4.2"
 serde = "1.0.208"
 serde_json = { version = "1.0.125", features = ["preserve_order"] }
 sqlx = { version = "0.8.0", features = ["runtime-tokio", "mysql", "tls-rustls"] }

src/server/command.rs

@@ -40,10 +40,6 @@ pub async fn handle_command(
 ) -> anyhow::Result<()> {
     let config = read_config_from_path_with_arg_overrides(config_path, args.config_overrides)?;
 
-    // if let Err(e) = &result {
-    //     eprintln!("{}", e);
-    // }
-
     match args.subcmd {
         ServerCommand::Listen => listen_for_incoming_connections(socket_path, config).await,
         ServerCommand::SocketActivate => socket_activate(config).await,
@@ -61,14 +57,12 @@ async fn socket_activate(config: ServerConfig) -> anyhow::Result<()> {
 }
 
 async fn get_socket_from_systemd() -> anyhow::Result<TokioUnixStream> {
-    let fd = std::env::var("LISTEN_FDS")
-        .context("LISTEN_FDS not set, not running under systemd?")?
-        .parse::<i32>()
-        .context("Failed to parse LISTEN_FDS")?;
+    let fd = sd_notify::listen_fds()
+        .context("Failed to get file descriptors from systemd")?
+        .next()
+        .context("No file descriptors received from systemd")?;
 
-    if fd != 1 {
-        return Err(anyhow::anyhow!("Unexpected LISTEN_FDS value: {}", fd));
-    }
+    log::debug!("Received file descriptor from systemd: {}", fd);
 
     let std_unix_stream = unsafe { StdUnixStream::from_raw_fd(fd) };
     let socket = TokioUnixStream::from_std(std_unix_stream)?;