feat(core): implement daemon process monitor in worker

espanso/src/cli/daemon/mod.rs

@@ -213,7 +213,7 @@ fn spawn_worker(paths: &Paths, exit_notify: Sender<i32>) {
     std::env::current_exe().expect("unable to obtain espanso executable location");
 
   let mut command = Command::new(&espanso_exe_path.to_string_lossy().to_string());
-  command.args(&["worker"]);
+  command.args(&["worker", "--monitor-daemon"]);
   command.env(
     "ESPANSO_CONFIG_DIR",
     paths.config.to_string_lossy().to_string(),

espanso/src/cli/worker/daemon_monitor.rs

@@ -0,0 +1,60 @@
+/*
+ * This file is part of espanso.
+ *
+ * Copyright (C) 2019-2021 Federico Terzi
+ *
+ * espanso is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * espanso is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+use std::{path::Path};
+
+use anyhow::Result;
+use crossbeam::channel::Sender;
+use log::{error, info, warn};
+
+use crate::lock::acquire_daemon_lock;
+
+const DAEMON_STATUS_CHECK_INTERVAL: u64 = 1000;
+
+pub fn initialize_and_spawn(runtime_dir: &Path, exit_notify: Sender<()>) -> Result<()> {
+  let runtime_dir_clone = runtime_dir.to_path_buf();
+  std::thread::Builder::new()
+    .name("daemon-monitor".to_string())
+    .spawn(move || {
+      daemon_monitor_main(&runtime_dir_clone, exit_notify.clone());
+    })?;
+
+  Ok(())
+}
+
+fn daemon_monitor_main(runtime_dir: &Path, exit_notify: Sender<()>) {
+  info!("monitoring the status of the daemon process");
+  
+  loop {
+    let is_daemon_lock_free = {
+      let lock = acquire_daemon_lock(runtime_dir);
+      lock.is_some()
+    };
+
+    if is_daemon_lock_free {
+      warn!("detected unexpected daemon termination, sending exit signal to the engine");
+      if let Err(error) = exit_notify.send(()) {
+        error!("unable to send daemon exit signal: {}", error);
+      }
+      break;
+    }
+
+    std::thread::sleep(std::time::Duration::from_millis(DAEMON_STATUS_CHECK_INTERVAL));
+  }
+}

espanso/src/cli/worker/mod.rs

@@ -20,13 +20,21 @@
 use crossbeam::channel::unbounded;
 use log::{error, info};
 
-use crate::{engine::event::ExitMode, exit_code::{WORKER_ALREADY_RUNNING, WORKER_EXIT_ALL_PROCESSES, WORKER_GENERAL_ERROR, WORKER_LEGACY_ALREADY_RUNNING, WORKER_RESTART, WORKER_SUCCESS}, lock::{acquire_legacy_lock, acquire_worker_lock}};
+use crate::{
+  engine::event::ExitMode,
+  exit_code::{
+    WORKER_ALREADY_RUNNING, WORKER_EXIT_ALL_PROCESSES, WORKER_GENERAL_ERROR,
+    WORKER_LEGACY_ALREADY_RUNNING, WORKER_RESTART, WORKER_SUCCESS,
+  },
+  lock::{acquire_legacy_lock, acquire_worker_lock},
+};
 
 use self::ui::util::convert_icon_paths_to_tray_vec;
 
 use super::{CliModule, CliModuleArgs};
 
 mod config;
+mod daemon_monitor;
 mod engine;
 mod ipc;
 mod match_cache;
@@ -47,6 +55,7 @@ pub fn new() -> CliModule {
 
 fn worker_main(args: CliModuleArgs) -> i32 {
   let paths = args.paths.expect("missing paths in worker main");
+  let cli_args = args.cli_args.expect("missing cli_args in worker main");
 
   // Avoid running multiple worker instances
   let lock_file = acquire_worker_lock(&paths.runtime);
@@ -104,9 +113,18 @@ fn worker_main(args: CliModuleArgs) -> i32 {
   .expect("unable to initialize engine");
 
   // Setup the IPC server
-  ipc::initialize_and_spawn(&paths.runtime, engine_exit_notify)
+  ipc::initialize_and_spawn(&paths.runtime, engine_exit_notify.clone())
     .expect("unable to initialize IPC server");
 
+  // If specified, automatically monitor the daemon status and
+  // terminate the worker if the daemon terminates
+  // This is needed to avoid "dangling" worker processes
+  // if the daemon crashes or is forcefully terminated.
+  if cli_args.is_present("monitor-daemon") {
+    daemon_monitor::initialize_and_spawn(&paths.runtime, engine_exit_notify.clone())
+      .expect("unable to initialize daemon monitor thread");
+  }
+
   eventloop
     .run(Box::new(move |event| {
       if let Err(error) = engine_ui_event_sender.send(event) {

espanso/src/main.rs

@@ -273,9 +273,8 @@ fn main() {
       SubCommand::with_name("worker")
         .setting(AppSettings::Hidden)
         .arg(
-          Arg::with_name("reload")
+          Arg::with_name("monitor-daemon")
-            .short("r")
+            .long("monitor-daemon")
-            .long("reload")
             .required(false)
             .takes_value(false),
         ),