rust_web_server/config_watch/
mod.rs

1//! Reload when the config file or a certificate changes (`watch = true`, #10).
2//!
3//! A background thread polls the size and modification time of
4//! `rws.config.toml` (or `RWS_CONFIG_FILE`) and of every configured TLS
5//! certificate and key once a second. A change that looks the same on two
6//! polls in a row — an editor or `certbot` finished writing — triggers the
7//! same validated reload as `SIGHUP` ([`crate::config_reload::request_reload`]):
8//! a broken config is rejected and the running one keeps serving. The set of
9//! files is re-read on every poll, so a reload that points at new
10//! certificates starts watching them. Off by default, like Caddy's `--watch`.
11
12use std::path::PathBuf;
13use std::time::{Duration, SystemTime};
14
15/// `RWS_CONFIG_WATCH`: `true` to reload when a watched file changes.
16pub const RWS_CONFIG_WATCH: &str = "RWS_CONFIG_WATCH";
17
18/// How often the files are checked.
19pub const POLL_INTERVAL: Duration = Duration::from_secs(1);
20
21/// Whether `RWS_CONFIG_WATCH` is on.
22pub fn enabled() -> bool {
23    std::env::var(RWS_CONFIG_WATCH).is_ok_and(|v| matches!(v.trim().to_ascii_lowercase().as_str(), "true" | "1" | "yes" | "on"))
24}
25
26/// The files whose change means a reload: the config file and every
27/// configured certificate and key (the default pair and each virtual host's).
28pub fn watched_paths() -> Vec<PathBuf> {
29    let var = |key: &str| std::env::var(key).ok().map(|v| v.trim().to_string()).filter(|v| !v.is_empty());
30    let mut paths = vec![PathBuf::from(var("RWS_CONFIG_FILE").unwrap_or_else(|| "rws.config.toml".to_string()))];
31    for key in [crate::entry_point::Config::RWS_CONFIG_TLS_CERT_FILE, crate::entry_point::Config::RWS_CONFIG_TLS_KEY_FILE] {
32        paths.extend(var(key).map(PathBuf::from));
33    }
34    // CRLs for client certificates: a new list applies without a restart.
35    if let Some(files) = var("RWS_CONFIG_TLS_CLIENT_CRL_FILE") {
36        paths.extend(files.split(',').map(str::trim).filter(|p| !p.is_empty()).map(PathBuf::from));
37    }
38    for i in 0.. {
39        if var(&format!("RWS_CONFIG_VIRTUAL_HOST_{i}_DOMAIN")).is_none() {
40            break;
41        }
42        for suffix in ["CERT_FILE", "KEY_FILE"] {
43            paths.extend(var(&format!("RWS_CONFIG_VIRTUAL_HOST_{i}_{suffix}")).map(PathBuf::from));
44        }
45    }
46    paths.sort();
47    paths.dedup();
48    paths
49}
50
51/// Size and modification time of each file (`None` while it doesn't exist).
52type Snapshot = Vec<(PathBuf, Option<(u64, SystemTime)>)>;
53
54fn snapshot(paths: Vec<PathBuf>) -> Snapshot {
55    paths
56        .into_iter()
57        .map(|path| {
58            let state = std::fs::metadata(&path).ok().and_then(|md| Some((md.len(), md.modified().ok()?)));
59            (path, state)
60        })
61        .collect()
62}
63
64/// Change detection, one [`Watcher::poll`] per interval.
65pub struct Watcher<F: FnMut() -> Vec<PathBuf>> {
66    paths: F,
67    applied: Snapshot,
68    pending: Option<Snapshot>,
69}
70
71impl<F: FnMut() -> Vec<PathBuf>> Watcher<F> {
72    /// A watcher of the files `paths` lists (asked again on every poll),
73    /// taking their current state as the applied one.
74    pub fn new(mut paths: F) -> Self {
75        let applied = snapshot(paths());
76        Watcher { paths, applied, pending: None }
77    }
78
79    /// `true` when the files changed and have stayed the same since the
80    /// previous poll: time to reload.
81    pub fn poll(&mut self) -> bool {
82        let now = snapshot((self.paths)());
83        if now == self.applied {
84            self.pending = None;
85            return false;
86        }
87        if self.pending.as_ref() == Some(&now) {
88            self.applied = now;
89            self.pending = None;
90            return true;
91        }
92        self.pending = Some(now);
93        false
94    }
95}
96
97/// Start the watcher thread when `RWS_CONFIG_WATCH` is on; the `rws` binary
98/// calls it after reading its configuration.
99pub fn start() {
100    if !enabled() {
101        return;
102    }
103    let spawned = std::thread::Builder::new().name("rws-config-watch".to_string()).spawn(|| {
104        let mut watcher = Watcher::new(watched_paths);
105        loop {
106            std::thread::sleep(POLL_INTERVAL);
107            if watcher.poll() {
108                println!("config watch: a watched file changed; reloading");
109                crate::config_reload::request_reload();
110            }
111        }
112    });
113    if let Err(e) = spawned {
114        eprintln!("config watch: could not start: {e}");
115    }
116}
117
118#[cfg(test)]
119mod tests;
rust_web_server/config_watch/mod.rs

rust_web_server/config_watch/
mod.rs
