fix(linux): add sd-notify for better systemd interop (#489)

Currently, services dependent on aw-server.service (e.g. aw-awatcher)
start just after its launch.

This patch causes systemd to launch the dependent services only after
the rocket server is up an running.

It's aimed to help slow systems to not close the dependent service
prematurely due to not being able to connect to the server.

Author: wojnilowicz

Diff for: aw-server.service

@@ -14,12 +14,12 @@
 #
 
 [Service]
-Type=simple
+Type=notify
 ExecStart=aw-server
 
 [Unit]
 Description=ActivityWatch Server (Rust implementation)
-Wants=network.target
+After=network.target
 
 [Install]
 WantedBy=default.target

Diff for: aw-server/Cargo.toml

@@ -35,6 +35,9 @@ aw-models = { path = "../aw-models" }
 aw-transform = { path = "../aw-transform" }
 aw-query = { path = "../aw-query" }
 
+[target.'cfg(target_os="linux")'.dependencies]
+sd-notify = "0.4.2"
+
 [target.'cfg(all(target_os="linux", target_arch="x86"))'.dependencies]
 jemallocator = "0.5.0"
 

Diff for: aw-server/src/main.rs

@@ -9,6 +9,8 @@ use clap::Parser;
 
 use aw_server::*;
 
+#[cfg(target_os = "linux")]
+use sd_notify::NotifyState;
 #[cfg(all(target_os = "linux", target_arch = "x86"))]
 extern crate jemallocator;
 #[cfg(all(target_os = "linux", target_arch = "x86"))]
@@ -147,9 +149,12 @@ async fn main() -> Result<(), rocket::Error> {
         device_id,
     };
 
-    let _ = endpoints::build_rocket(server_state, config)
-        .launch()
+    let _rocket = endpoints::build_rocket(server_state, config)
+        .ignite()
         .await?;
+    #[cfg(target_os = "linux")]
+    let _ = sd_notify::notify(true, &[NotifyState::Ready]);
+    _rocket.launch().await?;
 
     Ok(())
 }