Allow specifying polling/debounce frequency.

src/daemon.rs

@@ -14,9 +14,6 @@ use std::time::Duration;
 // TODO(jrpotter): Add logging.
 // TODO(jrpotter): Add pid file to only allow one daemon at a time.
 
-// Used for both polling and debouncing file system events.
-const WATCH_FREQUENCY: Duration = Duration::from_secs(5);
-
 // ========================================
 // Polling
 // ========================================
@@ -49,7 +46,7 @@ fn resolve_pending(tx: &Sender<DebouncedEvent>, pending: &HashSet<PathBuf>) -> V
     to_remove
 }
 
-fn poll_pending(tx: Sender<DebouncedEvent>, rx: Receiver<PollEvent>) {
+fn poll_pending(tx: Sender<DebouncedEvent>, rx: Receiver<PollEvent>, freq_secs: u64) {
     let mut pending = HashSet::new();
     loop {
         match rx.try_recv() {
@@ -61,7 +58,7 @@ fn poll_pending(tx: Sender<DebouncedEvent>, rx: Receiver<PollEvent>) {
                 resolve_pending(&tx, &pending).iter().for_each(|r| {
                     pending.remove(r);
                 });
-                thread::sleep(WATCH_FREQUENCY);
+                thread::sleep(Duration::from_secs(freq_secs));
             }
             Err(TryRecvError::Disconnected) => panic!("Polling channel closed."),
         }
@@ -142,7 +139,7 @@ impl<'a> WatchState<'a> {
 // Daemon
 // ========================================
 
-pub fn launch(mut config: PathConfig) -> Result<(), Box<dyn Error>> {
+pub fn launch(mut config: PathConfig, freq_secs: u64) -> Result<(), Box<dyn Error>> {
     let (poll_tx, poll_rx) = channel();
     let (watch_tx, watch_rx) = channel();
     let watch_tx1 = watch_tx.clone();
@@ -150,12 +147,12 @@ pub fn launch(mut config: PathConfig) -> Result<(), Box<dyn Error>> {
     // watch, but this fails if no file exists at the given path. In these
     // cases, we rely on a basic polling strategy to check if the files ever
     // come into existence.
-    thread::spawn(move || poll_pending(watch_tx, poll_rx));
+    thread::spawn(move || poll_pending(watch_tx, poll_rx, freq_secs));
     // Track our original config file separately from the other files that may
     // be defined in the config. We want to make sure we're always alerted on
     // changes to it for hot reloading purposes, and not worry that our wrapper
     // will ever clear it from its watch state.
-    let mut watcher: RecommendedWatcher = Watcher::new(watch_tx1, WATCH_FREQUENCY)?;
+    let mut watcher: RecommendedWatcher = Watcher::new(watch_tx1, Duration::from_secs(freq_secs))?;
     watcher.watch(&config.0, RecursiveMode::NonRecursive)?;
     let mut state = WatchState::new(poll_tx, &mut watcher)?;
     state.update(&config);

src/lib.rs

@@ -13,8 +13,8 @@ pub fn run_add(_config: PathConfig) -> Result<(), config::Error> {
     Ok(())
 }
 
-pub fn run_daemon(config: PathConfig) -> Result<(), Box<dyn Error>> {
-    daemon::launch(config)?;
+pub fn run_daemon(config: PathConfig, freq_secs: u64) -> Result<(), Box<dyn Error>> {
+    daemon::launch(config, freq_secs)?;
     Ok(())
 }
 

src/main.rs

@@ -19,7 +19,25 @@ fn main() {
                 .takes_value(true),
         )
         .subcommand(App::new("add").about("Add new configuration to local repository"))
-        .subcommand(App::new("daemon").about("Start up a new homesync daemon"))
+        .subcommand(
+            App::new("daemon")
+                .about("Start up a new homesync daemon")
+                .arg(
+                    Arg::new("frequency")
+                        .short('f')
+                        .long("frequency")
+                        .value_name("FREQUENCY")
+                        .help("How often (in seconds) we poll/debounce file system changes")
+                        .long_help(
+                            "There exists a balance between how responsive changes are \
+                    made and how expensive it is to look for changes. \
+                    Empirically we found the default value to offer a nice \
+                    compromise but this can be tweaked based on preference.",
+                        )
+                        .takes_value(true)
+                        .default_value("5"),
+                ),
+        )
         .subcommand(App::new("init").about("Initialize the homesync local repository"))
         .subcommand(App::new("list").about("See which packages homesync manages"))
         .subcommand(App::new("pull").about("Pull remote repository into local repository"))
@@ -44,7 +62,18 @@ fn dispatch(matches: clap::ArgMatches) -> Result<(), Box<dyn Error>> {
             let config = homesync::config::load(&candidates)?;
             match subcommand {
                 Some(("add", _)) => Ok(homesync::run_add(config)?),
-                Some(("daemon", _)) => Ok(homesync::run_daemon(config)?),
+                Some(("daemon", matches)) => {
+                    let freq_secs: u64 = match matches.value_of("frequency") {
+                        Some(f) => f.parse().unwrap_or(0),
+                        None => 5,
+                    };
+                    if freq_secs > 0 {
+                        homesync::run_daemon(config, freq_secs)?;
+                    } else {
+                        eprintln!("Invalid frequency. Expected a positive integer.");
+                    }
+                    Ok(())
+                }
                 Some(("list", _)) => Ok(homesync::run_list(config)?),
                 Some(("pull", _)) => Ok(homesync::run_pull(config)?),
                 Some(("push", _)) => Ok(homesync::run_push(config)?),